63 rear end clunk

[Harry S.]

Just looking for different opinions.

Symptom, I back up and hit the brakes and I get a clunk in the rear. It only happens once. When I go forward and hit the brakes I hear the clunk but it only happens once. This tells me something is shifting in the rear depending on direction.

I have a 64 style front differential bracket with the welded washer to go in with a new snubber. The 63 bracket I put in looked perfect when I put that in.

I removed the 4 spring plate bolts. They are the correct length 3 7/32. I put them back in and tightened the dog poop out of them.

Besides the holes being out of round on the front differential bracket, what else is there to look at?

Thanks

[Marco H.]

Re: 63 rear end clunk

Harry, Id check for movement in the pinion bracket, against the diff housing. Sounds like the bolts are tight enough for it not to rattle, but lose enough for the bracket to slightly shift. I would weld up the oval shaped holes. Most likely thats where your issue lies.
Another issue may be a worn pinion cushion which allows play/movement.
Hope this helps,
Marco

[Harry S.]

Re: 63 rear end clunk

Marco, agree with what you suggest. I do have the 64 style with the welded washer as well and new cushions (snubber). The hole in the 64 bracket is nice and round. Anything else you can think of?

[Marco H.]

Re: 63 rear end clunk

Harry, Only other items coming to mind are the condition/tightness of the upper crossmember cushions/bolts, and possibly the four bolts that hold the diff to the crossmember. (Rather unlikely). Ive seen several worn pinion brackets. So I believe you're on the right track.

[Frank D.]

Re: 63 rear end clunk

Am I understanding that you haven't installed the reinforced bracket yet ?
If not, what you are describing is a classic symptom of a "wallowed" out bolt hole... I can post the TSB if you like...
My next thought would be the snubber...

And, this may sound silly, but try running your scenario with everything out of the jack storage compartment and spare tire tub...
Don't even ask how I know this...

[Richard G.]

Re: 63 rear end clunk

Harry;
Add the half-shaft retaining clips/nuts to the inspection list. Axle and differential mounted yolks can also work on the splines. I have also observed worn differential spider gears cause this sound as the slack it taken up. Excessive side play, like if the washers are damaged or missing can cause this.
This is simple to check. Raise the car, block the wheels, put the car in neutral and move the drive-line back an forth. Also a good method to check the other areas for looseness. You can use a bar in the U-joint area for more leverage. Be careful and use large blocks or tie downs! Should have two people so one can turn and the other listen.
I would also inspect the brakes for the cause.

If after you have inspected everything and the clunk continues you may consider putting it over a pit, like the oil change places have.
Then you would be able to listen and watch as it is moved slightly forward and backwards.

The small traffic cams can also be mounted under the car long enough to move the car a foot or so.
Sometimes one has to be really innovative to track this stuff down.


Rick

[Timothy B.]

Re: 63 rear end clunk

Harry,

My experience is to raise the car leaving the weight on the tires, remove the front differential mount bolts and swing the mount down out of the way then remove the rubber bushing paying close attention to the top rubber bushing.

While the mount is hanging down you can look at the front holes and determine if the part is wore. Also, take a look at the tapped holes in the rear housing to make sure they don't look like they are starting to hammer oblong. If there is any gear oil seepage from around the pinion splines that will destroy the top rubber mount.

[Edward J.]

Re: 63 rear end clunk

Harry, to add to the checks, try the trailing arm bolts at the front. 63 had the shims that would fall out( early to mid I believe cars).

[Harry S.]

Re: 63 rear end clunk

Am I understanding that you haven't installed the reinforced bracket yet ?
If not, what you are describing is a classic symptom of a "wallowed" out bolt hole... I can post the TSB if you like...
My next thought would be the snubber...

And, this may sound silly, but try running your scenario with everything out of the jack storage compartment and spare tire tub...
Don't even ask how I know this...

Frank, All brackets and cushions are installed. The bracket and the cushions were in excellent shape when I installed them. I'm making the assumption that the front bracket has worn and is the culprit. I have replacement parts. I'm just looking for other suggestions. I like you test, I'll empty out the jack compartment.

Cheers

[Gary R.]

Re: 63 rear end clunk

I have seen some play in the splines of the outer axles and flanges, while the play was small and the parts still good you could feel the move, similar to backlash. while it most likely is not your issue you might as well check it when going over the car. If you hear a clicking sound that could be bad spiders but then you will know as they are on their last leg at that point.

As you know the brackets had issues until '69. The 63-4 front bolts are tapped and not through holes like 65-79's. Make sure they are tight.

[Frank D.]

Re: 63 rear end clunk

I have a reinforced bracket and, when this devilish hurricane passes, I have to change the pinion seal on my split window. Strongly considering putting the beefier bracket in at that time...

The reason I mentioned the spare tire tub is because I have an S-10 compact spare in there and it can move around a bit....makes more of a dull "thud" than a "clunk" though.

I started stuffing some packing foam around it to prevent the issue recently...

[Gary R.]

Re: 63 rear end clunk

I would use the 69-79 bracket if it were my car. Use a SKF/CR seal, pack the spring with grease and RTV on the OD. I now use Permashield on the splines of both the yoke and pinion.

[Frank D.]

Re: 63 rear end clunk

I would use the 69-79 bracket if it were my car. Use a SKF/CR seal, pack the spring with grease and RTV on the OD. I now use Permashield on the splines of both the yoke and pinion.

'Thanks - I literally just got back from NAPA and they had the seal on the shelf (surprised me) and it is an SKF...don't know if I'll need longer bolts for the reinforced bracket though...

Will do all the recommendations...(sorry for the sort of hijack Harry!)

[Duke W.]

Re: 63 rear end clunk

... could be wear on the backing plate pads that the sides of the shoes rest on. It can usually be corrected with a little filing to smooth out the typical "notch" that can form over the miles.

Duke

[Michael G.]