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Discussion Starter · #1 ·
I have a 1965 fastback mustang. It has a 302 in it along with a C4 transmission and 8inch rear axle. Im really not sure what my trouble is coming from. Whenenever i put it into drive or into reverse from neutral it seems to stall and then kick in. I had this problem before i put in a rebuilt transmission and ive also shanged the rear axle twice. I thought for sure this would fix it but I still have the problem. Its like the power builds up and then kicks in and its like a thud that can be felt. I thought it was play in the rear axle, but after changing it out twice im not so sure any more. any help would be greatly appreciated.
 

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Hello.:) :welcome: My first guess would be a torque converter problem, from what you describe, but it's not very easy to be certain without actually having the car here to check. You might want to consider taking the car to someone that you trust and that's familiar with automatic transmissions and have them check it out. :)
 

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thanks for the welcoming! I should of stated this earelier... I changed the torque converter when i changed the transmission. Ive had someone shif it while i looked under it and itll shift and then a second or so after it kicks in. I can see that the drive shaft will turn the differential jst enough without the tire turning or anything. This is where i will get the thud.
 

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Hi again.:) If you are saying that, when you put the car in ' Drive', the drive shaft will go around a half-turn or so without the wheels moving, and then there is a thunk, and then the wheels try to start turning, but that it does not do that when you put it in 'Reverse' , that's probably the backlash in the differential. If it also does that in reverse, you might have a busted or worn out tranny mount. But, if you can rotate the driveshaft a quarter of a turn or more by hand with the transmission in neutral and the rear wheels unable to turn, that's the differential. If you have changed the rear end out a couple of times, I would look for the common denominator. If the rear end was set up by the same guy, then that guy doesn't know what he's doing and has made the same set of mistakes in a very consistent manner.:gringreen
 

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OK...I want Veronica and others to check my logic on this but...

1) Put it in Park, chock the front wheels and jack the rear end up enough to get the tires off the ground and put some jack stands under the back (safety first).

2) Slowly rotate your drive wheel (if you have a posi you should be able to use either one).

3) Watch the rear end yoke where the drive shaft connects as you rotate your wheel. If the wheel turns a significant amount before the yoke begins to turn...it's slop in the rear end. If the yoke turns before the drive shaft starts to turn it's the rear u-joint.

4) If the yoke and drive shaft turn at the same time back up the wheel and watch the drive shaft/tranny yoke connection for slop. Slop there is the front u-joint.

5) If everything turns with no major slop the problem should be from the tranny forward.

I've had a beer or two so somebody double check me.
 

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Hi again.:) He doesn't have a U-joint problem. If it was a U-joint that was that bad, it would be doing a whole lot more than just one thunk and then take off ok from there. It would sound like a drum roll with sledge hammers as he went down the road, and, again, if it was a U-joint that was bad enough for the pinion to rotate far enough to be visible to the naked eye, there would also be a fair amount of lateral play. He would be able to grab the drive shaft with his hand and wiggle it around. Definitely not a U-joint. His problem is clearly either the differential, the torque converter, a transmission mount, or something inside the transmission, but I seriously doubt that it's something inside the transmission. It also might be that the description of the problem isn't really as detailed and accurate as it could be, since the title of the thread was something about either a tranny or rear end problem, and he ruled out the tranny and rear end straight out of the box.:gringreen It could be something as simple as he has the engine idle speed set way too high and it clunks when it goes into gear because of that. But, Montana's Stang, :) Lifting the car, putting it on jackstands and having someone put it in gear is a good idea. It would be very obvious where the noise is coming from then. That would be a very sensible, systematic approach to the problem. First, figure out what's making the noise. Then you figure out why.:)
 

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how about this!

:waveyHI! dne' here,
there are people that replace things without proper diagnosing. They do unwarranted work and spend hard earned money. I think it's this, so replace it without just cause. Do you think your rear end/third member was ok to begin with? You replaced it and does the same thing. you've replaced the the tranny and converter and still have the same thing. You know your u-joints are OK? a u-joint may look ok, but be totally rusted internally and upon inspection while installed in the car show no lateral movement or that of a typical worn out u-joint, or the clang associated when putting the car in gear. If you had the driveshaft out, its usually instinct to grasp the joints and move them around checking them~ did you do that.
Specifically a sound making a 'thud' sound reminds me of a bad left side motor support.

insanity: doing the same thing over and over again and expecting different results.
 
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