Thanks for sharing, interesting. I have a similar issue, definitely not as bad, Im thinking is the aluminum driveshaft, should be looking into it at some point in Sept.
Drivetrain clunk greatly reduced...for now
Just wanted to share my troubleshooting journey with everyone. I finally found a major cause of my drivetrain clunk and managed to reduce it to a barely perceivable level. TL;DR at the bottom.
A little bit of history: the clunk started to manifest less than 6 months after the car was driven off the dealer lot. Everything was still stock. Basically, the simplest way to explain it would be whenever there was a difference in the chassis's momentum vs. the driveline's forward or backward thrust. So situations like going from reverse to forward, letting off the throttle and then back on again, or clutching in and out during shifts. It would sound semi-metallic and slightly deadened, but clearly came from the rear or middle of the car. It got worse over time until I installed the AM Alum 1-Piece driveshaft (Axle Exchange), which pretty much eliminated that clunk altogether. Sure, I could make some sort of noise back there if I shifted like a tard, but I think that's the case with any manual.
About a year later, the clunk started coming back again. Based on extensive research on the InterWebz (and because I was going to upgrade the suspension anyway), I installed the Steeda Street UCA, J&M LCA's, Steeda PHB+Brace, Steeda Sport springs, and Koni Yellows. Got it back from the mechanic and immediately noticed it was still there. It was a more solid feeling/sounding clunk, but still present nonetheless. So, after more forum lurking, I thought it might be the (2mm?) bolt hole size difference between the UCA and the mount. Even though the Steeda UCA included stepped-spacers (which my mechanic confirms he installed), I didn't want to take any chances so I had the Steeda UCA Mount installed. Still had the clunk.
Then, I had my mechanic check the rear-end's ring gear backlash. It was completely in-spec. Actually very tight, he noted. At the same time I changed out the rear diff fluid to RP 75W-140 (maybe mixed with 0.5 qts of 75W-90 because Pep Boys had just run out of the former). The rear end got a little quieter in terms of gear noise, but I still had the same clunk. I didn't think it had much to do with the rear-end to begin with, but I crossed that off the list anyway. Also at the same time, I had the pinion angle re-verified for the 3rd time, making sure that the -2 degrees was relative to the angle of the transmission flange, not the ground or the drive shaft itself. All was fine there too. Not that an improper pinion angle was likely to cause a clunk, but whatever...I was running out of things to check.
At this point, I couldn't think of what else it could be and decided to leave it alone and try to live with it. Especially since many have said "it's normal" and that all Mustangs "have a clunky drivetrain to a certain degree". Now, it's true that there are those typical small thud and clacking noises from the transmission or rear-end, but I've always felt like this clunk wasn't exactly "normal" since, to me, it seemed like it also delayed the time it took for the car's weight to transfer front-to-back.
Couple months later, I installed the BMR LCA Relocation Brackets. Instructions said bolt-in only for street was OK! Got a bunch of new noises from what felt like a slightly pivoting rear axle that would clunk on hard turns or going up ramps sideways. Eventually I had my mechanic weld them in. Other than a little increase in road noise, there were no more "falling apart" noises were coming from the rear suspension so I was back to just the driveline clunk.
Note: after installing the brackets, it was getting hard to get into gear...almost as if I never changed transmission fluid from OEM to BG SS II and also kept the factory shifter bushing. It turned out that while my rear axle thrust angle was always slightly off from the factory, it became out of spec after installing the brackets. I switched to Whiteline adjustable LCA's and had an alignment shop put thrust angle as close to 0.0 as possible and re-centered the rear axle via adjustable panhard bar. This made it much easier to get into gear while shifting.
Fast forward to about a month ago. I happened to run across a post on another forum that described the symptoms I had, IE - same ways to produce the clunk. He had a stock drive shaft and fixed the problem by re-greasing the slip joint. I contacted my drive shaft manufacturer (Axle Exchange) and asked if this was something that needed to be maintained over the life of the drive shaft. Mark said that the grease is sealed by a rubber boot over the splines and that some customers never have to re-grease it. However, if I shipped the drive shaft back to them, they would inspect the U-Joints and the re-grease the slip for me, no charge (except for shipping to). Since I really didn't want to ship an entire drive shaft from CA to NJ, I asked if he could provide instructions on how to do it myself. Mark actually did one better and shipped me the proper clamps/grease and gave detailed instructions over the phone!
So finally, this past weekend, I managed to find some time to take apart the slip joint. There was grease inside, covering all the splines, but it felt a little bit thin. Maybe the grease had deteriorated being so close to the exhaust, not sure. I applied all the grease that was provided covering as much of both male and female ends of the joint as possible. After reinstalling the drive shaft, almost ALL of the clunk was gone. It's as close to the feeling and sound of when I first installed the drive shaft. The only time I can still get it to barely make a "thud"is if I let off in 5th or 6th under 2k RPM and quickly get back on it.
However, I've read elsewhere that sometimes the clunk comes back after a couple months. One possible solution...use more grease. Pack a bunch into the bottom of the female end of the slip joint. But what I'm thinking is that the heat from the exhaust pipes are making the grease more viscous over time, resulting in the slip joint not providing enough driveline shock absorption...or something like that. Maybe putting heat wrap around that section of the exhaust might make the grease last longer.
In any case, just thought I'd share my experience of troubleshooting this "normal" clunk. I'm sure others could have figured this out much faster, but doing all this research and messing with stuff under the car for the past year actually helped me know my car a little better. Anyways, hope this helps others with similar issues and levels of OCD.
TL;DR:
I've went through a good number of things to check while troubleshooting a driveline and/or rear suspension clunk. I'm sure this is just a subset of possible problem areas, but here's what I've personally found. The re-greasing of the drive shaft slip joint is what ultimately fixed it for me.
Possible causes of drivetrain or rear suspension clunk:
- drive shaft slip joint needs re-greasing
- rear upper control arm mounting hole too big
- rear-end ring gear backlash out of spec
- rear-end gear oil low or low quality
- pinion angle out of spec
- rear axle thrust angle out of spec
- driver shift behavior
Solutions or actions taken:
- re-grease slip joint
- stepped spacers or replace UCA mount
- check and/or shim ring gear backlash
- replace rear-end gear oil
- verify pinion angle
- adjustable LCA to correct thrust angle
- analyze clutch/shift timing, faster/slower, maintain momentum
Results:
- clunk reduced to almost nothing
- slightly more solid rear-end feeling
- no effect, was in-spec
- small reduction in rear-end gear noise
- no effect, was in-spec
- car no longer "dogtracking", less resistance getting into gear
- developed consistent shift timing to base "clunk" observations on
A little bit of history: the clunk started to manifest less than 6 months after the car was driven off the dealer lot. Everything was still stock. Basically, the simplest way to explain it would be whenever there was a difference in the chassis's momentum vs. the driveline's forward or backward thrust. So situations like going from reverse to forward, letting off the throttle and then back on again, or clutching in and out during shifts. It would sound semi-metallic and slightly deadened, but clearly came from the rear or middle of the car. It got worse over time until I installed the AM Alum 1-Piece driveshaft (Axle Exchange), which pretty much eliminated that clunk altogether. Sure, I could make some sort of noise back there if I shifted like a tard, but I think that's the case with any manual.
About a year later, the clunk started coming back again. Based on extensive research on the InterWebz (and because I was going to upgrade the suspension anyway), I installed the Steeda Street UCA, J&M LCA's, Steeda PHB+Brace, Steeda Sport springs, and Koni Yellows. Got it back from the mechanic and immediately noticed it was still there. It was a more solid feeling/sounding clunk, but still present nonetheless. So, after more forum lurking, I thought it might be the (2mm?) bolt hole size difference between the UCA and the mount. Even though the Steeda UCA included stepped-spacers (which my mechanic confirms he installed), I didn't want to take any chances so I had the Steeda UCA Mount installed. Still had the clunk.
Then, I had my mechanic check the rear-end's ring gear backlash. It was completely in-spec. Actually very tight, he noted. At the same time I changed out the rear diff fluid to RP 75W-140 (maybe mixed with 0.5 qts of 75W-90 because Pep Boys had just run out of the former). The rear end got a little quieter in terms of gear noise, but I still had the same clunk. I didn't think it had much to do with the rear-end to begin with, but I crossed that off the list anyway. Also at the same time, I had the pinion angle re-verified for the 3rd time, making sure that the -2 degrees was relative to the angle of the transmission flange, not the ground or the drive shaft itself. All was fine there too. Not that an improper pinion angle was likely to cause a clunk, but whatever...I was running out of things to check.
At this point, I couldn't think of what else it could be and decided to leave it alone and try to live with it. Especially since many have said "it's normal" and that all Mustangs "have a clunky drivetrain to a certain degree". Now, it's true that there are those typical small thud and clacking noises from the transmission or rear-end, but I've always felt like this clunk wasn't exactly "normal" since, to me, it seemed like it also delayed the time it took for the car's weight to transfer front-to-back.
Couple months later, I installed the BMR LCA Relocation Brackets. Instructions said bolt-in only for street was OK! Got a bunch of new noises from what felt like a slightly pivoting rear axle that would clunk on hard turns or going up ramps sideways. Eventually I had my mechanic weld them in. Other than a little increase in road noise, there were no more "falling apart" noises were coming from the rear suspension so I was back to just the driveline clunk.
Note: after installing the brackets, it was getting hard to get into gear...almost as if I never changed transmission fluid from OEM to BG SS II and also kept the factory shifter bushing. It turned out that while my rear axle thrust angle was always slightly off from the factory, it became out of spec after installing the brackets. I switched to Whiteline adjustable LCA's and had an alignment shop put thrust angle as close to 0.0 as possible and re-centered the rear axle via adjustable panhard bar. This made it much easier to get into gear while shifting.
Fast forward to about a month ago. I happened to run across a post on another forum that described the symptoms I had, IE - same ways to produce the clunk. He had a stock drive shaft and fixed the problem by re-greasing the slip joint. I contacted my drive shaft manufacturer (Axle Exchange) and asked if this was something that needed to be maintained over the life of the drive shaft. Mark said that the grease is sealed by a rubber boot over the splines and that some customers never have to re-grease it. However, if I shipped the drive shaft back to them, they would inspect the U-Joints and the re-grease the slip for me, no charge (except for shipping to). Since I really didn't want to ship an entire drive shaft from CA to NJ, I asked if he could provide instructions on how to do it myself. Mark actually did one better and shipped me the proper clamps/grease and gave detailed instructions over the phone!
So finally, this past weekend, I managed to find some time to take apart the slip joint. There was grease inside, covering all the splines, but it felt a little bit thin. Maybe the grease had deteriorated being so close to the exhaust, not sure. I applied all the grease that was provided covering as much of both male and female ends of the joint as possible. After reinstalling the drive shaft, almost ALL of the clunk was gone. It's as close to the feeling and sound of when I first installed the drive shaft. The only time I can still get it to barely make a "thud"is if I let off in 5th or 6th under 2k RPM and quickly get back on it.
However, I've read elsewhere that sometimes the clunk comes back after a couple months. One possible solution...use more grease. Pack a bunch into the bottom of the female end of the slip joint. But what I'm thinking is that the heat from the exhaust pipes are making the grease more viscous over time, resulting in the slip joint not providing enough driveline shock absorption...or something like that. Maybe putting heat wrap around that section of the exhaust might make the grease last longer.
In any case, just thought I'd share my experience of troubleshooting this "normal" clunk. I'm sure others could have figured this out much faster, but doing all this research and messing with stuff under the car for the past year actually helped me know my car a little better. Anyways, hope this helps others with similar issues and levels of OCD.
TL;DR:
I've went through a good number of things to check while troubleshooting a driveline and/or rear suspension clunk. I'm sure this is just a subset of possible problem areas, but here's what I've personally found. The re-greasing of the drive shaft slip joint is what ultimately fixed it for me.
Possible causes of drivetrain or rear suspension clunk:
- drive shaft slip joint needs re-greasing
- rear upper control arm mounting hole too big
- rear-end ring gear backlash out of spec
- rear-end gear oil low or low quality
- pinion angle out of spec
- rear axle thrust angle out of spec
- driver shift behavior
Solutions or actions taken:
- re-grease slip joint
- stepped spacers or replace UCA mount
- check and/or shim ring gear backlash
- replace rear-end gear oil
- verify pinion angle
- adjustable LCA to correct thrust angle
- analyze clutch/shift timing, faster/slower, maintain momentum
Results:
- clunk reduced to almost nothing
- slightly more solid rear-end feeling
- no effect, was in-spec
- small reduction in rear-end gear noise
- no effect, was in-spec
- car no longer "dogtracking", less resistance getting into gear
- developed consistent shift timing to base "clunk" observations on
1 - 16 of 16 Posts
Mine has done that since new, thank you for confirming exactly what I thought it was. I'm going to get a real suspension shop to check my alignment, I didn't get the printout from the rack when I dropped it at the dealer for first service. I figured it was the spline joint, but your work was not done in vain.Just wanted to share my troubleshooting journey with everyone. I finally found a major cause of my drivetrain clunk and managed to reduce it to a barely perceivable level. TL;DR at the bottom.
A little bit of history: the clunk started to manifest less than 6 months after the car was driven off the dealer lot. Everything was still stock. Basically, the simplest way to explain it would be whenever there was a difference in the chassis's momentum vs. the driveline's forward or backward thrust. So situations like going from reverse to forward, letting off the throttle and then back on again, or clutching in and out during shifts. It would sound semi-metallic and slightly deadened, but clearly came from the rear or middle of the car. It got worse over time until I installed the AM Alum 1-Piece driveshaft (Axle Exchange), which pretty much eliminated that clunk altogether. Sure, I could make some sort of noise back there if I shifted like a tard, but I think that's the case with any manual.
About a year later, the clunk started coming back again. Based on extensive research on the InterWebz (and because I was going to upgrade the suspension anyway), I installed the Steeda Street UCA, J&M LCA's, Steeda PHB+Brace, Steeda Sport springs, and Koni Yellows. Got it back from the mechanic and immediately noticed it was still there. It was a more solid feeling/sounding clunk, but still present nonetheless. So, after more forum lurking, I thought it might be the (2mm?) bolt hole size difference between the UCA and the mount. Even though the Steeda UCA included stepped-spacers (which my mechanic confirms he installed), I didn't want to take any chances so I had the Steeda UCA Mount installed. Still had the clunk.
Then, I had my mechanic check the rear-end's ring gear backlash. It was completely in-spec. Actually very tight, he noted. At the same time I changed out the rear diff fluid to RP 75W-140 (maybe mixed with 0.5 qts of 75W-90 because Pep Boys had just run out of the former). The rear end got a little quieter in terms of gear noise, but I still had the same clunk. I didn't think it had much to do with the rear-end to begin with, but I crossed that off the list anyway. Also at the same time, I had the pinion angle re-verified for the 3rd time, making sure that the -2 degrees was relative to the angle of the transmission flange, not the ground or the drive shaft itself. All was fine there too. Not that an improper pinion angle was likely to cause a clunk, but whatever...I was running out of things to check.
At this point, I couldn't think of what else it could be and decided to leave it alone and try to live with it. Especially since many have said "it's normal" and that all Mustangs "have a clunky drivetrain to a certain degree". Now, it's true that there are those typical small thud and clacking noises from the transmission or rear-end, but I've always felt like this clunk wasn't exactly "normal" since, to me, it seemed like it also delayed the time it took for the car's weight to transfer front-to-back.
Couple months later, I installed the BMR LCA Relocation Brackets. Instructions said bolt-in only for street was OK! Got a bunch of new noises from what felt like a slightly pivoting rear axle that would clunk on hard turns or going up ramps sideways. Eventually I had my mechanic weld them in. Other than a little increase in road noise, there were no more "falling apart" noises were coming from the rear suspension so I was back to just the driveline clunk.
Note: after installing the brackets, it was getting hard to get into gear...almost as if I never changed transmission fluid from OEM to BG SS II and also kept the factory shifter bushing. It turned out that while my rear axle thrust angle was always slightly off from the factory, it became out of spec after installing the brackets. I switched to Whiteline adjustable LCA's and had an alignment shop put thrust angle as close to 0.0 as possible and re-centered the rear axle via adjustable panhard bar. This made it much easier to get into gear while shifting.
Fast forward to about a month ago. I happened to run across a post on another forum that described the symptoms I had, IE - same ways to produce the clunk. He had a stock drive shaft and fixed the problem by re-greasing the slip joint. I contacted my drive shaft manufacturer (Axle Exchange) and asked if this was something that needed to be maintained over the life of the drive shaft. Mark said that the grease is sealed by a rubber boot over the splines and that some customers never have to re-grease it. However, if I shipped the drive shaft back to them, they would inspect the U-Joints and the re-grease the slip for me, no charge (except for shipping to). Since I really didn't want to ship an entire drive shaft from CA to NJ, I asked if he could provide instructions on how to do it myself. Mark actually did one better and shipped me the proper clamps/grease and gave detailed instructions over the phone!
So finally, this past weekend, I managed to find some time to take apart the slip joint. There was grease inside, covering all the splines, but it felt a little bit thin. Maybe the grease had deteriorated being so close to the exhaust, not sure. I applied all the grease that was provided covering as much of both male and female ends of the joint as possible. After reinstalling the drive shaft, almost ALL of the clunk was gone. It's as close to the feeling and sound of when I first installed the drive shaft. The only time I can still get it to barely make a "thud"is if I let off in 5th or 6th under 2k RPM and quickly get back on it.
However, I've read elsewhere that sometimes the clunk comes back after a couple months. One possible solution...use more grease. Pack a bunch into the bottom of the female end of the slip joint. But what I'm thinking is that the heat from the exhaust pipes are making the grease more viscous over time, resulting in the slip joint not providing enough driveline shock absorption...or something like that. Maybe putting heat wrap around that section of the exhaust might make the grease last longer.
In any case, just thought I'd share my experience of troubleshooting this "normal" clunk. I'm sure others could have figured this out much faster, but doing all this research and messing with stuff under the car for the past year actually helped me know my car a little better. Anyways, hope this helps others with similar issues and levels of OCD.
TL;DR:
I've went through a good number of things to check while troubleshooting a driveline and/or rear suspension clunk. I'm sure this is just a subset of possible problem areas, but here's what I've personally found. The re-greasing of the drive shaft slip joint is what ultimately fixed it for me.
Possible causes of drivetrain or rear suspension clunk:
- drive shaft slip joint needs re-greasing
- rear upper control arm mounting hole too big
- rear-end ring gear backlash out of spec
- rear-end gear oil low or low quality
- pinion angle out of spec
- rear axle thrust angle out of spec
- driver shift behavior
Solutions or actions taken:
- re-grease slip joint
- stepped spacers or replace UCA mount
- check and/or shim ring gear backlash
- replace rear-end gear oil
- verify pinion angle
- adjustable LCA to correct thrust angle
- analyze clutch/shift timing, faster/slower, maintain momentum
Results:
- clunk reduced to almost nothing
- slightly more solid rear-end feeling
- no effect, was in-spec
- small reduction in rear-end gear noise
- no effect, was in-spec
- car no longer "dogtracking", less resistance getting into gear
- developed consistent shift timing to base "clunk" observations on
Well done!
Sometimes OCD can be a good thing....thx for the info/post.
Sometimes OCD can be a good thing....thx for the info/post.
One more thing that I thought of since yesterday. It occurred to me that I didn't remove all of the old grease from the splines before applying the new grease. This was probably not the best idea. If my theory is correct, the old heat-cycled grease has become less viscous and should be removed altogether so that the slip can expand/contract with the characteristics of the fresh grease. I'm guessing that this may be related to why the clunk returns quicker than expected for some people.
GM has a special grease just for spline clunk.
if your clunk returns, I would try some of the GM stuff.
if your clunk returns, I would try some of the GM stuff.
I've heard of the GM stuff mentioned on a lot of truck forums. I think it's this stuff. Don't think I need 1 lb. of it so hopefully it comes in a smaller tube somewhere.GM has a special grease just for spline clunk.
if your clunk returns, I would try some of the GM stuff.
I've also heard good things about Motorcraft XG-8 PTFE Lube.
Does anyone know what these feel like? IE - tacky, thick, runny, thin, goopy? The grease the Axle Exchange (AE) sent me was some industrial SKU in the Shell Gadus family. Problem is, I can't tell which model it is, so I'm not sure about its chemical composition. It's near-black and it's pretty thick and tacky so at least I don't think it's lithium-based. I would assume that any alternative would probably need to have roughly the same consistency as the stuff AE provided for heat resistance and shock load. Mark from AE suggested something Moly-based would be pretty good.
And oh, for reference, the sizes of the two single-use ear-clamps that go on both sides of the rubber slip joint boot are 82mm and 95mm. They are Oetiker stepless hose clamps that look like this. I assume those were the min diameter figures. It was recommended that these specific clamps were used and also replaced in the exact same position because the DS is balanced with them on.
Were the splines plastic coated? Also, packing too much grease in there may hydrolock it and force grease out the relief hole (assuming it has one).
The splines were blue-colored on the male end which I assume means it's plastic-coated like the stock DS spline would be.
I didn't see a relief hole, but manually moving it in and out produced a sort of gassing sound.
When I had it apart, the inside of the female end actually had a good amount of space (maybe 2") past the splines. So I'm thinking some additional grease, without completely filling that chamber, wouldn't be too much of a problem.
The clunk was the most apparent when transitioning from coasting to accelerating and I think that's when the slip contracts. So maybe some extra grease where the male end meets the deepest part of the female end would provide some buffering.
Damn...is it just me, or were there a lot of sexual innuendos in this post??
I didn't see a relief hole, but manually moving it in and out produced a sort of gassing sound.
When I had it apart, the inside of the female end actually had a good amount of space (maybe 2") past the splines. So I'm thinking some additional grease, without completely filling that chamber, wouldn't be too much of a problem.
The clunk was the most apparent when transitioning from coasting to accelerating and I think that's when the slip contracts. So maybe some extra grease where the male end meets the deepest part of the female end would provide some buffering.
Damn...is it just me, or were there a lot of sexual innuendos in this post??
You're just making it too hard.
Does anyone have an update to this thread? The description of the clunk is exactly what I have heard/felt, but I am certainly not eager to exchange all those parts in pursuit of a solution.
I just got an explanation from the dealer for my 2014 stock 3.7 automatic. He said the issue is "drive-line lash" and the clunk is coming from the slip yoke. Since Ford was calling this normal behavior for all Mustangs (they test drove three other 2014s) I asked about aftermarket drive shafts and perhaps there was an alternate way to get rid of the clunk. The adviser said that eliminating the lash would damage the differential. This is my 5th Mustang and the only rear drive car I've ever driven that had drive-line lash.
I just got an explanation from the dealer for my 2014 stock 3.7 automatic. He said the issue is "drive-line lash" and the clunk is coming from the slip yoke. Since Ford was calling this normal behavior for all Mustangs (they test drove three other 2014s) I asked about aftermarket drive shafts and perhaps there was an alternate way to get rid of the clunk. The adviser said that eliminating the lash would damage the differential. This is my 5th Mustang and the only rear drive car I've ever driven that had drive-line lash.
good writing! I wonder why I didn't read this earlier.
Yes going to a one piece "can" damage the rear end, the reason ford went to a 2 piece DS was to limit the abuse on the rear end, the GT500 as a one piece but it's carbon fiber so it allows for flex because it's carbon fiber. As for actual damage caused by the single piece it's not typical, many people have had less issues with the single than the 2 piece. If you want the added security of the less abuse on the rear end and the the added security for the 1 piece the carbon fiber DS is about 1200 if you can find them. Good luck
Sent from AutoGuide.com Free App
Sent from AutoGuide.com Free App
Looking for a update on this thread - Will an application of grease to the "stock" drive shaft slip joint fix a 2-1 down shift clunk? - (6r80) auto transmission 2-1 down shift clunk?
It might it is a common occurrence on the F-150 and that is the fix on them.
1 - 16 of 16 Posts
- This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
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