WMD - 8 May - Rear Suspension work

[HIZNHRZ]

Jim and Yun, a serious thank you helping to think through the latest set of actions, each helping to improve the listing of my Z?s back end from passengers side to drivers side. At it?s worst point last year, the passengers side was an inch and a half higher than the drivers side. We have improved the situation to where the delta is now less than 1/2". The average ZR-1 is has a 1/4" or less difference between the height of the drivers and passenger sides.

Prior to yesterday and at separate times the stock rear leaf spring bolts and castle nuts were replaced and adjusted with longer bolts. These are the parts that are sold as the rear end lowering kit. While using the bolts to lower the car, the ride height problem also improved about a half of an inch.

The rear leaf spring was then removed and inspected. It looked just as one would expect the leaf spring of a low mileage ZR-1 to look. Because you can?t always see a defect, we rotated the leaf spring 180 degrees when we put it back in. No difference in ride height was noted.

Yesterdays objective was to first inspect the position of the bat wing relative to the ground. Not surprisingly, the left side was still higher. We then measure several chassis point to ground and verified the same difference between the passenger and drivers side. There appears to be little that can be done to adjust out the height difference. What we did, however, was loosen the front and rear C-beam bolts and jack up the back end of the car. We artificially corrected the listing problem by jacking up the drivers side inch and a half higher than the passenger side. We then tightened the C-beam bolts, lowered the car, drove it and re-measured ride height. There was a 5/8? improvement verifying Yun?s theory that the C-beam was in tension. We tried the same approach by loosening, jacking up, and retightening the bolts that hold the bat wing to the frame. No further improvement was noted.

At this point the car is 3/8" to a 1/2" off level. While this is a little more than the average Z it is a whole lot better than it was. Thanks again guys.

I'll post some pictures when I get a chance.

[QB93Z]

It was an interesting day. I learned a few things about the C4 suspension. There is no doubt that the body list (leaning to one side) is determined by the differential housing batwing position. There is no "adjustment point" for the body height. The batwing is rigidly attached to the transmission/engine by the c-beam. The engine is mounted to the frame at the motor mounts.

We attempted to change the body tilt by taking all of the slack/movement in the c-beam connections in the same direction. In the pic you can see the wood block on the driver's side of the frame with the c-beam bolts loosened. Then we tightened the bolts and revoved the jack.



We were able have an effect on the side to side height difference but we couldn't get all of the tilt out.

Jim

[Scrrem]

Sorry I missed, but got my shed completed today, start emptying the garage today, so time was well spent.

OK, from what I am reading in your post Jim, does that mean that possibly the frame is twisted since the batwing is catty-wompas?
Rich

[QB93Z]

It has got to be a feeling of accomplishment to get the shed finished and start clearing out the garage. Next the lift.

I do not think the frame is twisted. I suspect that the remaining 1/2" may be in suspension components, either front or rear.

Jim

[secondchance]

Originally Posted by HIZNHRZ

Jim and Yun, a serious thank you helping to think through the latest set of actions, each helping to improve the listing of my Z?s back end from passengers side to drivers side. At it?s worst point last year, the passengers side was an inch and a half higher than the drivers side. We have improved the situation to where the delta is now less than 1/2". The average ZR-1 is has a 1/4" or less difference between the height of the drivers and passenger sides.

Prior to yesterday and at separate times the stock rear leaf spring bolts and castle nuts were replaced and adjusted with longer bolts. These are the parts that are sold as the rear end lowering kit. While using the bolts to lower the car, the ride height problem also improved about a half of an inch.

The rear leaf spring was then removed and inspected. It looked just as one would expect the leaf spring of a low mileage ZR-1 to look. Because you can?t always see a defect, we rotated the leaf spring 180 degrees when we put it back in. No difference in ride height was noted.

Yesterdays objective was to first inspect the position of the bat wing relative to the ground. Not surprisingly, the left side was still higher. We then measure several chassis point to ground and verified the same difference between the passenger and drivers side. There appears to be little that can be done to adjust out the height difference. What we did, however, was loosen the front and rear C-beam bolts and jack up the back end of the car. We artificially corrected the listing problem by jacking up the drivers side inch and a half higher than the passenger side. We then tightened the C-beam bolts, lowered the car, drove it and re-measured ride height. There was a 5/8? improvement verifying Yun?s theory that the C-beam was in tension. We tried the same approach by loosening, jacking up, and retightening the bolts that hold the bat wing to the frame. No further improvement was noted.

At this point the car is 3/8" to a 1/2" off level. While this is a little more than the average Z it is a whole lot better than it was. Thanks again guys.

I'll post some pictures when I get a chance.

No need to thank me Scott.
So many, including Jim, David and so forth, have been generous with their help in solving mysteries and helping me get my car back to where it is now.
I feel I owe the same to all ZR-1 brothers (and sisters if they are out there).