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240 Clunk/looseness in rear end after M47 swap

cmsuter

cmsuter

Member
Joined
Feb 11, 2019
Recently Completed an M47 swap (from AW70) in my 92 244. When I hit the throttle or let off, there is a clunk in the rear end. You can definitely feel it. My initial thought was torque rods but I double checked and they are definitely tight (double checked every bushings and nut/bolt in the rear end). All the bushings are about 2 years old and all SuproPro poly bushings. All the U-joints are brand new (Moog) and the center support bearing and bushings are new. Any ideas? It feels like just a whole lot of play in the rear end, which wouldn't be so crazy since it has 275k miles, but it didn't do it before the swap.
 
The suspension is pretty good at loading up and hiding slop. In addition to /\ /\ /\ you might try putting it in 1st/reverse and on level ground, hand brake off, rock the car back and forth, see if it clunks in an easier to find setting. Also try it in neutral with the handbrake on.

Another clunk that hid from me a bit in a sneaky way is the double-sided rear shock mount. The bolt holding the shock on can be snug, but the back side of that bolt has to be tightly bolted through the subframe.
 
If you don't find excessive play in the ring/pinion gears, my bet is on your Poly bushings. They wear out excessively fast and leave about 1/32-1/16" slop around the steel sleeve. Enough that with a manual transmission, they pop/clunk all the time.
 
Here's an old pic from my 244DL with this exact issue:

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EDIT - and a Youtube clip! https://youtu.be/KyAltmjkrMg
 
If I could do it again, I probably wouldn't go Poly. I was a Volvo noobie and was due for bushings. The price of Poly vs OE Volvo rubber was appealing as well as the ease of installation. But regardless, it wasn't doing any of this when I had the automatic, so I'm skeptical that the poly is the issue.
 
I swapped my 244DL from AW70 to M47 in 2009 and I noticed this same thing. The automatic and driveline don't move around as much as the M47 setup. Whenever I actually start working on the car again, I am installing a new axle with Ben's spherical TABs, hybrid torque rods and spherical panhard bar.
 
cmsuter said:
If I could do it again, I probably wouldn't go Poly. I was a Volvo noobie and was due for bushings. The price of Poly vs OE Volvo rubber was appealing as well as the ease of installation. But regardless, it wasn't doing any of this when I had the automatic, so I'm skeptical that the poly is the issue.
Click to expand...

An automatic transmission does a much smoother job accelerating/decelerating than a manual transmission does. the slip in the converter covers up all kinds of chassis problems. I've driven automatics with torque rod bushings so shot they move 1/2" and yet, they didn't clunk. The car would wander because the rear axle was steering it. The same situation with a manual transmission will thump/clunk every time the transmission is shifted or throttle is applied/released.
 
2manyturbos said:
An automatic transmission does a much smoother job accelerating/decelerating than a manual transmission does. the slip in the converter covers up all kinds of chassis problems. I've driven automatics with torque rod bushings so shot they move 1/2" and yet, they didn't clunk. The car would wander because the rear axle was steering it. The same situation with a manual transmission will thump/clunk every time the transmission is shifted or throttle is applied/released.
Click to expand...

I just drove a car the other day that had torque rod bushings that were completely shot and yet no clunk. I was very surprised. My M47 244 has a combo of rubber/poly. Poly in torque rod/panhard bar, front control arms. Everywhere else rubber and I have no clunks or squeaks. Drives very well for what it is
 
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