Hello all.

I have an 83 FB with 2.8L Vin 1 5spd that has a problem that has been driving me and my mechanic nuts.

The car shifts and drives forward fine all the time. Reverse is a different story. The car will reverse fine when its cold. Drive it for about 10 miles and the trouble starts.

After the car has been driven for about 10 miles, putting the trans into reverse just to park the car makes the tranny lug like I'm trying to start out in 3rd gear going forward. The problem is so bad I once had to drive around the block to park the car because it would not go back 20 feet. The only way to get the car to move in reverse is to race the engine and severally slip the clutch which doesn't do anybody any good.

My mechanic watched me back up and said that he could see the driver's side rear wheel hopping, but he can't find anything in the suspension or drivetrain that would allow for it. Everything looks fine.

The clutch is new, the flywheel was recently resurfaced, new shocks and springs all around, and it has a rebuilt T5 with less than 1,000 miles on it.

I'm stumped. Any input would be appreciated.

Thanks,
Joe

 

Just a thought here.

My mechanic found that the torque arm insulators at the tranny end of the torque arm are bad.

Is it possible that bad torque arm insulators could allow for enough change in the driveline angle to cause resistance in reverse?

Are the insulators the same as the Energy Suspension torque arm mount bushings sold on Jeg's?

 

I thought that I would post an entry to this thread even though I am the only one who has posted anything to it. I am doing this in case anyone else has had the same problem that I described.

The following is a thread that I started in the V6 group regarding flywheel availability:
https://www.thirdgen.org/techbb2/sho...hreadid=210125

It turned out that the problem with getting the car to move in reverse without lugging was based in the flywheel. According to my mechanic, there was some old documentation talking about a problem with warping of the flywheel on the externally balanced 2.8L after is reaching operating temperature or higher.

I replaced the flywheel from the source described in the other thread and the problem is fixed.

 

Good fault finding there!
Was the car doing strange things in the forward gears when warm? Surely if the flywheel was warping when warm it would at least judder-even when going forward?
Do you or your mechanic know why it warps?

Andy.

 

Hi Andy.

I wish I could say it was good fault finding. Alot of it was trial and error both on my and my mechanic's part because we were stumped.

The strange thing about the problem was that the car ran through all five forward gears fine. There was what seemed to be more than the normal engine vibration at higher RPMs. Other than that, the only thing that I notice different now is that the old clutch, which was replaced in May 03 and had less than 1000 miles on it, had a harsh engagement. I would have to concentrate to keep it from banging at times.

At times, there was some juddering, but I attribute that to my trying too hard to find it. I would be concentrating so hard on hearing and feeling the clutch that I wouldn't give it enough gas or would give it too much clutch. Aside from the occasional harsh engagement, there was no discernible problem when I just "became the car" and drove it with my focus on traffic.

That was the kicker. The clutch had been replaced in May 03, the T5 had been replaced a couple of months ago, the rear drum brakes were wearing fine, and the rear was opened up and found to have no problems. Forward fine. Reverse not so fine. And we both concluded that the addition of MAC SFCs magnified the problem.

My mechanic talked to a couple of his buddies who remember having read old GM docs about flywheel warping on the 2.8L. Apparently, it has to do with the bell shape of the flywheel when viewed on edge. As the flywheel heats, the pressure of the clutch forces the flywheel to bend backward slightly. (The only thing that I can compare it to would be placing a Frisbee on top of a soda can (i.e. the crankshaft) and lightly pressing down on the ribs on the top of the Frisbee.) This, as I understand it, somehow put a greater load on the engine because driveline components that should be straight were bending slightly. The bending was reducing the ability to transfer the power from the engine and increasing the heat in the flywheel.

This was occuring in the forward gears but not as badly as reverse because the load on the rear wheels is different in reverse than it is going forward. As you go forward, the front of the car wants to rise. In reverse, the front of the car is forced down which, I guess, increases drag which, in turn, increases the load on the engine. The SFCs magnified the problem because there was no flex in the body.

So, now I have a new reman flywheel, new reman T5 with a Hurst shifter, and a better, higher performance clutch in place. For the first time in 3 years since we've had the car, it reverses fine.

Now to tackle the sound system. . .

Joe

 

Wow.
Thanks for the comrehensive reply! I like the coke can and frisbee explanation! Very clear.
Good job your mechanic and his friends have a good memory! Makes you wonder how the problem was discovered all those years ago. Some very clever people around.
Again, thanks for the reply. Always good to hear how problems are solved. This will surely help others out.

Good luck with your sound system and your future project! Must be nice to know another major hurdle is solved.

Andy.

 

You're welcome, Andy!

Yeah, this was a hurdle that was stressing me out. I had put a good chunk of change into the restoring of the body of the car. (It is my daughter's car and we are doing the Knight Rider thing.) I didn't want to give it back to her unless it was 100% drivable. So, I've been stressing over it since May 03 taking care of the mechanical hard-to-find, hard-to-do, and hard-to-get-done items before moving forward with the audio and restoring the interior.

I've spent a good deal of time in Thirdgen boards looking for answers. I've found many that have helped me with my T/A's (two 87s) and her FB. A detailed solution to an unusual problem is the least I could add to the sum of knowledge already here.

If it helps one other person, the job cost me half as much.

Joe