Need advice on transmission - Ford Mustang Forum
 
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post #1 of 12 (permalink) Old 09-12-2017 Thread Starter
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Need advice on transmission

Hi All. I have an 07 mustang gt with 127k on it. I just put on some longtube headers and I only plan on keeping the car another 3-5 years. Probably closer to 4 years. The past couple months I have been driving around with my trans grinding gears from the 2-3 upshift only when cold. When I dropped my car off last weekend to get the headers put on, 1-2 started to grind too I'm thinking now with the headers, I wanna enjoy and get the most out of the car and I don't want to let the transmission ruin that for me so I will get it fixed in a month or too. My question is should I get a used one or rebuild mine? I noticed if I buy a rebuilt one a lot of the times they want your transmission back as a core charge which means paying return shipping on my end. I have money but I really would like saving a couple hundred bucks here. I also am not sure about how trust worthy people/places are when it comes to listing mileage on the transmissions. Has anyone here had any luck with used 3650's? What would you do if you were me? Thanks for any replies!

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post #2 of 12 (permalink) Old 09-12-2017
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are you still on the original shifter/motor mounts/transmission mount/transmission fluid? all of these account for hard shifting, being locked out at high rpms etc, all the issues you are having. your transmission is probably fine. do yourself a favor and invest in an MGW shifter, poly motor mounts (should have done with the long tubes), poly transmission mount and a drain and fill of 3.2 quarts of Mobil1 synthetic auto transmission fluid. if your motor mounts are shot, your motor twists as it revs putting strain on the input shaft of the transmission and that twisting tightens the gears basically and you cant shift till you let off the gas, letting the engine fall back on the worn mounts, easing the stress thru the transmission. also, the headers didn't really gain you much but sound, not as much as you think, TBH. good luck

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post #3 of 12 (permalink) Old 09-12-2017 Thread Starter
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Transmission fluid was replaced last october. Person doing the install said the motor mounts were ok. Also Poly ones can cause clearance issues with Longtubes. I never get locked out of gear when shifting at even 6k. My only issues are with shifting while cold. I've been considering the mgw shifter but most things I've read have lead me to believe I have worn out Synchros. Transmission mounts were something I thought could help also but I honestly believe it's just worn out synchro's. There is 127k on it after all. A huge reason I did headers was sound and I bought used American Racing Headers. My car got Dyno'd at 303 RWHP even with that mileage! My only other Mod is a Roush CAI. If he did a before Dyno I will post both sheets. I'm fairly certain Roush CAI with a tune would Dyno high 280's at best based on what I've seen. I don't believe there are very many options to make power with these cars. I understand Cams would have made a little bit more gains and would have been more cost effective possibly (probably not as I got a good labor quote for the headers and bought used) but I'm not a fan of the rough idle.
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post #4 of 12 (permalink) Old 09-18-2017
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Originally Posted by NAs197 View Post
Transmission fluid was replaced last october. . . . . My only issues are with shifting while cold. . . . I honestly believe it's just worn out synchro's. There is 127k on it after all. . . . .
What fluid did you use? In my experience it does not make a big difference, but the best synthetics are a little better when cold.

I guess the crunching shifts have gotten worse lately; did not happen in the past?

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post #5 of 12 (permalink) Old 09-18-2017
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Where are you located? I may have a 3650 for sale. It'd just mean decommissioning my parts car. Lol

Current:
2007 Mustang GT 302 stroker 6060 swap, 3.73 gears, Hidden Hitch Receiver, Barton Short Throw, JBA LTs, Borla Touring Axle Back, Lito tuned SCT X4. BMR SP009, Bilsteins, J&M CC plates, J&M LCAs. 4 Piston Brembos
DOB GT450 with VMP Gen II 2.3 TVS | 13/14 GT500 HE & IWP | GT500 hat & DW340s | FRPP 52lb | CMS Stage 2 Blower Cams | Comp 113 Springs & Retainers | 8 rib conversion | Track Spec GT500 Vents | PTFE Heat Barriers
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post #6 of 12 (permalink) Old 09-18-2017
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Assuming the fluid is good, it sounds like either the TO bearing is not traveling the correct distance or the syncro rings are worn........ either way, those are pretty cheap to replace as compared to an outright rebuild/replacement

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post #7 of 12 (permalink) Old 09-19-2017
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your OEM motor mounts are shot. Period. there is a cup that goes over them so you really cant see how bad they are. they are collapsed and allow the engine to twist when revved and while trying to shift. your shop knows no better and that's on both of you. poly mounts will work for your setup but your shop didn't want to do the work. your engine right now is sitting about 1/2" lower than it should cuz the mounts are shot. quit bitching about hard shifts and fix the easy problems and be done with it. you will however experience a bit more NVH but not much, especially if you can shift thru the gears. good luck
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post #8 of 12 (permalink) Old 09-20-2017 Thread Starter
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What fluid did you use? In my experience it does not make a big difference, but the best synthetics are a little better when cold.

I guess the crunching shifts have gotten worse lately; did not happen in the past?
Whatever OEM fluid is, that's what I used. I think Mercon V if I'm not mistaken. It did not happen in the past and I think it might have gotten worse lately but it's hard to tell.
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post #9 of 12 (permalink) Old 09-20-2017 Thread Starter
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Where are you located? I may have a 3650 for sale. It'd just mean decommissioning my parts car. Lol
I live in Southeastern PA.
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Ah, I'm in Southwest AL. Shipping would probably cost nearly as much as the transmission.

Current:
2007 Mustang GT 302 stroker 6060 swap, 3.73 gears, Hidden Hitch Receiver, Barton Short Throw, JBA LTs, Borla Touring Axle Back, Lito tuned SCT X4. BMR SP009, Bilsteins, J&M CC plates, J&M LCAs. 4 Piston Brembos
DOB GT450 with VMP Gen II 2.3 TVS | 13/14 GT500 HE & IWP | GT500 hat & DW340s | FRPP 52lb | CMS Stage 2 Blower Cams | Comp 113 Springs & Retainers | 8 rib conversion | Track Spec GT500 Vents | PTFE Heat Barriers
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Whatever OEM fluid is, that's what I used. I think Mercon V if I'm not mistaken. It did not happen in the past and I think it might have gotten worse lately but it's hard to tell.

Does it 100% only happen when cold?

Honestly, I would drain the tranny fluid yourself. The shop probably botched the job with too much or too little or used garbage fluid.

Use mobil 1 synthing ATF mercon V and when you drain the fluid, it is imperative that the car is parallel l to the floor and gravity so it all comes out of the pan. So basically all 4 sides on jacks. 3.2 quarts exactly. Tranny's are sensitive to this - I've ever heard of bad things happen even when guys use 1/8th of a quart more than 3.2 quarts.



I mean this is the only thing that has changed and it was working fine last year right? It's the cheapest thing to start off at. $30-$40 for the fluid at advance auto parts.
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post #12 of 12 (permalink) Old 09-30-2017 Thread Starter
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Does it 100% only happen when cold?

Honestly, I would drain the tranny fluid yourself. The shop probably botched the job with too much or too little or used garbage fluid.

Use mobil 1 synthing ATF mercon V and when you drain the fluid, it is imperative that the car is parallel l to the floor and gravity so it all comes out of the pan. So basically all 4 sides on jacks. 3.2 quarts exactly. Tranny's are sensitive to this - I've ever heard of bad things happen even when guys use 1/8th of a quart more than 3.2 quarts.



I mean this is the only thing that has changed and it was working fine last year right? It's the cheapest thing to start off at. $30-$40 for the fluid at advance auto parts.
The 1 to 2 shift pretty much grinds every time now. It went bad quickly once it started. The 2-3 grinds only when cold. It has been that way for over 6 months. I trust the shop that did the job, they do good work and I had the fluid level checked when I got headers installed. Also something I didn't mention is the input shaft bearing is definitely bad as when the car is in neutral and my foot isn't on the clutch, i can hear a slight noise (it's not throwout bearing noise, I'm familiar with what that sounds like). i was going to start with just the fluid but that noise pretty much confirms it's not in the best shape. I'm pretty sure the transmission is in need of a partial rebuild as are multiple mechanics I had check it out. I decided I'm going to buy a used one and sell my broken one and just hope for the best that I got a good one.
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