Strange clunking noise

[pdplot]

Drove '71 TR-6 into garage after usual in-town run. Everything fine. Next morning, drove out of the garage and heard a strange noise when I let the clutch out. Sounded like it came from just back of the transmission. Thereafter, everytime I accelerated hard, I heard and felt the clunk. Might be a front universal? Motor mounts seem fine - engine secure on its mounts. Any ideas? Thanks.

PD Plotnick - Stamford, CT

 

[mrv8q]

Broken differential mount pin? LOTS of discussion on this very subject....

 

[TR3driver]

But check the U-joints first, they're a lot easier to check (and replace).

 

[M_Pied_Lourd]

Check your shocks/shock links as well just for fun.

Cheers,
M. Pied Lourd

 

[kodanja]

U-JOINTS~!!!!!!!


DIFFY MOUNTS'

 

[bnw]

I did a nuts and bolts 76 tr6 in 1990. I had a clunk. I replaced all the u-joints. I replaced the rear dif mounts with the upgraded poly units. I even replaced the half shafts. The clunk never went away. I drove the car 30,000 miles over 16 years. The clunk never went away. Good luck!

 

[BritBox]

Lots of good suggestions so far. Here's one that's a little more far-fetched:

If your differential's pinion gear has started backing away from the crown gear for any reason, you will get a clunk similar to what you are experiencing. The pinion shifts front to back as it loads and unloads from when you get on the gas and then the brakes.

It's something to consider after you check the more likely scenarios.

 

[HerronScott]

I'd check u-joints first , then rear transmission mount and finally the differential mounts.

Scott

 

[hondo402000]

If you are still running the lever shocks check the bolts that hold the lever shocks to the frame, they work loose but usually that clunk is when you go over bumps

Hondo

 

[poolboy]

If you have the original type rear differential mounts, they have an inner metal sleeve that surrounds the mounting pin.
Whatever adhesive they used to bind the metal sleeve to the rubber can give out. When that sleeve comes loose a sudden change in speed will cause the sleeve to clunk, clank? against the pin.
I don't think it hurts anything, but it does make you wonder if you gave a cracked right front mount or worn axle shaft splines.

 

[DanB]

Probably is the differential mount. Opposite corners of it break loose from the frame under torque. If the frame isn't rusted out it can be welded.

Dan B

 

[pdplot]

Thanks for all the suggestions. You guys are great. When I get some time, I'll take the car to a shop and have them put it up on the lift. When I drove the car again yesterday, it seemed to come from the left side under my seat and made the noise when I backed off the gas abruptly, not under acceleration.

PD

 

[YYCDave]

One other thing to check is the axle splines. If they're not fully lubricated they can bind up a bit and give a bit of a clunk. Do you notice any noises from the rear when cornering? If so that could also be a symptom of dry splines. Fairly easy to deal with, be sure to use the gray Moly type grease.

 

[startech47]

Exhaust pipe hitting frame or floor pan?

 

[Dino_V]

I had a similar sound coming from around the rear diff area, and later realized it was just the exhaust.

 

[Rrbbeerrttoo]

The only clunk I ever heard during accel or dec in my tr4a turned out to be a bad right rear u-joint

 

[pdplot]

Put the car on a lift today. Good mechanic could find nothing wrong. All bolts tight, motor & tranny mounts tight, tube shocks ok, etc. Slight play in both rear wheels but its always had that. One chrome exhaust extension was loose & rattling but that wasn't the clunk when accelerating or decelerating with force. Drive the car smoothly and there's no noise (other than the usual TR rattles & bangs over bumps). I'm stumped.

PD

 

[M_Pied_Lourd]

Anything loose in the trunk like the Jack or something else rolling around?

Cheers,
M. Pied Lourd

 

[Andrew Mace]

Nothing against your 'good' mechanic, but sometimes it takes a good bit of brute force to detect a worn/broken mount, u-joint, etc. I'm thinking good-size pry bar kind of brute force. Apologies to your mechanic if he/she used same....

 

[TR3driver]

Nothing against your 'good' mechanic, but sometimes it takes a good bit of brute force to detect a worn/broken mount, u-joint, etc. I'm thinking good-size pry bar kind of brute force. Apologies to your mechanic if he/she used same....

Indeed, I've heard similar stories where even a big pry bar wouldn't produce the clunk. But once the diff was dropped and a good light used, it became obvious that the mounting studs were tearing their way out of the frame.

160 ft-lb, times about 3:1 in first gear means some 480 ft-lb being applied to the diff in one dimension, plus 480 times 3.7 in another. Hard to match that with a pry bar!