Alright guys, first time poster here. Usually I can figure out everything I need to know by reading but this ones giving me some trouble. Ok, I just got done w/ my tranny swap on my 99 Jimmy 4dr 4wd. I got it together drove it for almost a week with no problems, shifted good, everything. Just the other day though, I left school and was driving down the road when I heard a wierd..."chirping" sort of noise. I got it home and put it up on the lift and realized it was coming form the bell-housing. I pulled the inspection hole cover and realized there was some scoring on the block to the engine side of the flexplate around where the torque converter bolts would be, so I pulled the starter figuring somehow one of the bolts loosened up. I checked the bolts and they were all tight so I threw the starter back on and started it up and went underneath to take a look and realized the felxplate had a nasty wobble to it. I've started tearing it back apart to put a new flexplate in but I want to know what could've caused it to get bent. I read somewhere if the T.C. isn't removed properly it will cause some sort of allignment to be thrown off. When putting the trans up my buddy wasn't paying attention and the T.C. slid out and fell about 4 feet onto the concrete floor but seem undamaged and slid right back in. Any ideas guys, all input appreciated. Thanks

 

If your transmission bolts came loose that will cause that too

 

I just split the tranny from the motor last night and all the bellhousing bolts were tight.

 

Been a while since I`v pulled\dealt with a flex plate. If I remember there are small weights to balance them. One may have been jarred loose in the fall, or loosened just enough to let go during the RPMs while driving. I`m guessing the second since toy were able to drive it without any problems initially.

 

Flexplate was never loosened up during the swap. It stayed attached to the engine the whole time.

 

Sorry. Mis-read. You are saying the torque converter hit the floor.

Last time I dealt with a TC was the last time I dealt with a flex plate. I know the TCs are balanced as well. Not sure if it`s via external weights or not.

 

There are several ways to warp a flexplate.
Loose mounting bolts, since you didnt remove it, I doubt thats the problem.

Loose flexplate/torque converter bolts, or loose starter bolts. Sounds like you ruled both of thsoe out as well.

Loose tranny to engine bolts, or you didn't reinstall the support brackets and the tranny/engine has been flexing, warping the flewplate. I believe in '98 GM went to the aluminum oil pan which bolts to the tranny and eliminated the support brackets.

Your torque converter is warped from the fall or it sustained internal damage during the fall and did cause the damage to the flexplate.

You must pull the torque converter and flexplate to inspect and replace. While you have them out look for damage.
No need to remoave the tranny from teh truck completely. Take a bellhousing bolt to ACE Hardware and buy 4 bolts about 6"-8" long. Remove the lower 4 bellhousing bolts and replace witht he longer versions. Remove the top two bellhousing bolts, remove driveshaft(s), t-case/tranny suuport bracket, tranny cooler lines, unbolt torque converter from flexplate, and anything else in the way. Then slide the tranny back as far as possible, you should have enough room to remove both the flexplate and torque converter. Lay the torque converter on a flat level surface and take mearurements to see if its warped. I hope you didnt damage the tranny pump. That isn't cheap to replace, and it only takes a scratch no thicker than your finger nail to damage the face. That scratch will lead to total tranny failure.

 

If it is bent, and wasn't before the install, I would guess it got bent when you bolted up the converter. They are pretty thin, and are prone to cracking. Been a while since I have installed a TC, but I used to put it on and spin it both directions a bit to be sure it is seated correctly. If it is not It will put stress on the flex plate.

 

The TC just slid out...idk if that would affect the pump or not. Will any damage to the pump be quite obvious when inspecting?