View Full Version : Broken diff mounts???

09-05-2008, 09:02 AM
I love driving my recently finished 4a, but have this pesky "clunk" in the rear half of the car. Before everyone jumps on the "it's broken diff mounts" bandwagon, let me give some background. I had the body off the frame and the frame stripped down to nothing. Then I had the frame sandblasted to bare metal. At that point, I spent lots of time inspecting the diff mounts as well as other suspension areas (both front lower A-frame brackets were cracked) and didn't see ANY signs of cracking, stress or cause for alarm around the diff pins. Is it possible these are fine and the noise is coming from something else? Has anyone had this problem before? Are there any audio clips of what a broken diff pin sounds like???

Thanks for the help!

67 4a

09-05-2008, 09:34 AM
You might need to also check your universal joints. Those can make that clunking noise. When were those last replaced?

09-05-2008, 11:01 AM
Or the differential has a lot of play in it.

09-05-2008, 03:45 PM
Thanks for the quick replies! I should have elaborated a bit - when I did the body off resto, there was no bolt, rubber, or U-joint that didn't get replaced. All U-joints are new, but I could have screwed up installing one as they were buggers to get in correctly.

Could the half-shaft splines be causing the problem? These are original and I've noticed some play in them...

Andrew Mace
09-05-2008, 03:48 PM
I'm not clear on exactly when this clunk happens. Depending, one other common cause is nothing more than a loose lever shock absorber. Worth checking out as well.

09-05-2008, 04:26 PM
The clunk happens when I let the clutch out - starting off, shifting, etc - and when I go over some bumps.

Rear shocks are converted to piston style. It's *possible* I have a bad shock (new) or adapter plate...

09-05-2008, 07:27 PM
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Rear shocks are converted to piston style. It's *possible* I have a bad shock (new) or adapter plate...[/QUOTE]

Or loose plates. Those should be checked after the first 500 miles and every season after that. That advice came from a friend who had the same problem after converting and now does that tightening regularly.

Oh, welcome to the forum!

11-18-2008, 05:05 PM
I wanted to follow up and let the group know of an issue I resolved. First,
thanks to everyone who has provided help / feedback over the past year I've
been hunting the cause of this issue.

The car is a 1967 TR4A, IRS; the issue is a rear end clunk upon take-off,
shift, and bumps. Having welded in enough extra support and reinforcement to
the IRS pins while the frame was bare, I was pretty certain I could cross
these off the list of possible causes. I even swapped out a diff unit
thinking it was a bad inner bearing (any one need a spare IRS diff??), but
still had the issue. It wasn't until I had bought a second hand half shaft
and was about to dismantle it to clean and check that I noticed there was
absolutely *NO* play in the sliding splines! I checked the axels on the car,
and sure enough, you could hear a very faint 'click' when you rotated the
halves against each other. Upon further inspection of the donor axle, I
found the splines to be heavily smeared with grease. Mine weren't of course
because I had cleaned them up nicely and didn't give thought to really
packing the grease in. After packing the grease in the spline cavity and
reassembling, I had a quiet and smooth riding 4A!

Moral of the story - if it slides, rotates, or rubs, pack it full of

1967 TR4A, no clunk, clink, or clank!

11-18-2008, 07:38 PM

Welcome to the forum and thanks for the update. I have a similar knock that's been driving me nuts. I too checked everything: u-joints, diff mounting pins, shocks, even had a used diff rebuilt by Quantum Mechanics and the knock is still there. I suspected the half-shafts, but now I'm going to check them out for sure come spring. Come on spring!:c

11-18-2008, 09:35 PM
Also if you have wire wheels check the splines on the hubs/wheels.