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Clunking Sound from differential

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jerrybny

jerrybny

Jedi Knight
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I think TR6 driving season may be over. :-(. I am getting a clunking sound out of my differential when shifting from 1st to 2nd and 2nd to 3rd on my 73 TR6. Is it time for a differential rebuild? Was in the high 70's and 80's this week in NY. Sure glad I did a lot of driving this last week. Thanks in advance for all responses.
 
I'd have a quick check of the halfshafts if you didn't already.

It might be that one is loose or has a 'tired' u-joint if you are really lucky. Mine clunks going into and out of reverse for this exact reason. I initially thought the diff was broken until I had them out for something else.

Good luck...
 
Have you checked the diff mounts? They have a tendency to slowly crack even with no rust involved. The first one to go is usually the front passenger side.

To check this jack up the rear of the car and you should be able to see both of the front mounts, use your finger to feel where the bolt feeds through the bottom of the mount.
 
Sometimes the clunk, if not too great, is play in the halfshaft splines, which I have. All of my u-joints are new. I did replace the really worn halfshafts with some "good" used orignals, but there is still some play on taking up drive. From what I have read and been told it is something to live with. The case hardening on the splines should last a good long while.
Plus some of the clunk is actual wear in the diff itself, which has at leat 80K miles. Again this could go on for ages before a major problem occurs. There is no whining or other nasty noises under power or "on the overrun" as the Brits say. I'll live with both until the noise becomes too unbearable.
A clunk when shifting gears when already on the move warrants closer examination. Check the diff mounts as suggested.
 
Unfortunatly the only way to uncover the problem is to examine the drive train. Start with the u-joints, looking for looseness by rotating back & forth. This is not always easy to spot, there should be no rotational play between the two parts.
Next check the trany mounts, these are often overlooked & are often worn or broken (soaked in gear oil).
Axle spline wear is pretty much a given on most cars but you usually won't get it in the higher gears. You should also remove them for inspection & repack them with a quality moly base grease. This helps with hard shift binding as well.
The diff mounts are a weak point & need to be looked over carefully. Check for cracks at the "bridge" where the stud passes through. If these are in need of repair TRF has a pdf template available on line to make steel plates to box these in & reinfoce the mounts.
Last but not least is the diff itself. This unit has a bad rap & is certainly not the beefiest unit ever made but I know of many hard driven cars with over 100,000 miles on original units. It's a crap shoot to get a good one it seems. The side carrier spider gears have a fiber washer that wears .

There's alot to look over & the drive train has always had slop issues, so unless it's unusally bad it just might be normal, what ever that is.
 
I have it up on jack stands with the tires off. I had the wife put it in gear and then sit depress and release the clutch while I was underneath the rear. Every once in awhile I would hear the clunk when she popped the clutch. Wouldn't this elimnate the mounts(not that I'm not gonna check them while I'm down there)? It sure sounds like its coming from the differential. I also put my hand on the bottom of the differential and I swear I can feel it when it clunks, though maybe the feel is normal. I will look at everything that was suggested. Would it hurt anything to remove the outer axle shaft assembly to see if it goes away? That way there I have it down to the differential or the driveshaft connections. Thanks
 
Make sure When you jack the car up you put blocks under the rear trailing arm & lower the car to simulate normal stub axle angle. Not only is it not good for the U-joints to be stressed but you will mask any looseness .
Unless the clunk is extreme , it's normal to get some clunk from the diff. You will also notice some movement of the entire diff on the rubber mounts. Check these for cracks & deterioration. If I remember corectly , you should not have more than 1/2" of rotation of the axle if you hold the pinion flange. This is certainly not scientific or an accurate measurment but it's a baseline for the obvious.
 
Well maybe I lucked out. I found a bad inner u-joint that was really really loose. It didn't even have a grease fitting. I am gonna replace all six and keep my fingers crossed that this was the problem and not the differential. Thanks to all who responded with suggestions. I checked them all.
 
Well I was finally able to get the 6 out after replacing all the u-joints. The good news is that they seemed to have been the problem. The clunking noise is gone.
thanks for all the suggestions guys.
 
Yeah, I'm glad you sorted that one out. I didn't think it was diff mounts. Mine never clunked when they went South. They chirped like a little bird was following me around. The chirp was the metal on both sides of the cracked mount rubbing against each other. What a pain to fix that one! Ugh!
 
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