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TR4/4A TR4A IRS Rear Spring Bridge

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KVH

KVH

Obi Wan
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I'm getting a little bang or "kick in the rear" on two occassions: a) taking off from a stop while letting the clutch out; and b)shifting at high rpms.

I'm told to check the rear bridge securing studs and the half axle splines and u-joints.

Any advice and suggestions as what to check first, and how?

I'd like it to be something easy like u-joints, but that thump seems to be coming from the center/rear, which makes me worry it's something more tedious to address.

My car does have a Nissan RX200 LSD Differential.

thx
 
It is difficult, and I can't tell what may have to be loosened before being checked.

Any real examination may require removal of the mufflers.

It doesn't look very roomy up there.

I'm really discouraged by all the "literature" about how the frame components on the IRS models are supposedly fragile in this area, needing welded strap iron supports and other upgrades available from Revington TR, Moss, Roadster Factory, etc.

It appears that a thorough removal and reinstallation of the differential and half shafts may be indicated in many cases--just to be sure everything is healthy.

I guess I might be headed in that direction, and would love to be talked out of it.
 
You can see it pretty well from the wheel well when you take one of the rear tires off. Usually the two mounting studs that are diagonally opposed to each other, (one front, one rear) pull out under torque. I have repaired mine a few times. The first time we actually cut holes in the rear shelf with a holesaw and used round electrical plugs to plug the holes when we were done. Welded down through the hole. Later, I had the frame off and did a better job. You do have to drop the pumpkin to repair it though.

Dan B
South Charleston WV
 
Dan, you actually cut circular holes out thru the top of the rear shelf to access the top of the spring bridge?

How large?

Then, you weld down thru that hole to fasten the bolt?

Is it hard to control the welding equipment inside the car in close quarters like that?

How hard is it to drop the differential? Hours?

thx
 
I would have hoped that if someone spent the money and effort to put the Nissan differential in that they would have addressed any issues in this area.

Dropping the standard differential isn't hard other than balancing the differential on a jack while removing it and reinstalling it. Remove any exhaust pieces that are in the way. Remove 12 nuts and bolts for the half-shafts and driveshaft. Remove the 4 nuts for the differential mounts and lower the differential. I'm not familiar with the Nissan replacement though.

Scott
 
I agree with Scott. Dropping the diff is pretty easy. As far as the holes in the rear shelf are concerned, we went to an hardware store and found the biggest sheet metal plug we could find (round) and got a holesaw the same size. Yes you have to stick weld from the top through the hole, so it is key to get the hole centered pretty much over the attachment.
I would recommend dropping the pumpkin and taking a look at everything there before pulling any interior. Depending on what kind of damage you have, you may be able to address it from the bottom. A lift would certainly be helpful if you have access to one. I did mine on jackstands.
 
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