Question: Flex Plate Replacement -- do able?? Anyone done it??

[dmdodd]

Guys/Gals,

I'm certain that the flexplate on my '79 L-48 has lost some teeth and therefore won't turn-over (I'm inspecting this weekend to makesure it's not just the starter solenoid work, as audibly you can hear the starter rotoring the gear and grinding a little).

Anyways, heard it's a real heartache.
Any advice? ;help
Anyone got some info on where I can get the procedure from and torque ratings on the plate bolts?
Tools needed? Heard a transmission jack is essential - gonna be expensive, I wonder if I can hire one...

Thanks once again.

~Dan

 

[Evolution1980]

It would serve you well to the get Assembly Instruction Manual ("AIM") as it will have everything you need to know.
I didn't feel like replacing mine when it lost some teeth, so I just bought a brand new crate engine with a flexplate already on it.
But seriously...even if someone here can chime in with the answer, it's a good idea to get the AIM. If you are willing to tackle a job like this, you're probably willing to do other larger jobs and the AIM can be a great resource for all those jobs.

 

[killain]

I wouldn't consider it a particularly difficult job, might take you five hours or so. 1. Disconnest battery, Get a 1979 AIM, & disconnect the driveshaft & crossmember bolts, cap the tailshaft so you don't lose fluid 2. take out the bolts at the bellhousing, remove the flywheel cover and fluid lines and the torque converter to flexplate & seperate the transmission from the engine, move it back about five or six inches. 3. remove the six crankshaft bolts, remover the flex-plate, fit the new flex plate ( Make sure it has the exact same number of teeth) and is same dia. use a little medium loctite on the crankshaft bolts and torque the bolts to the specs in the AIM. 4. fit the transmission back onto the engine and tighten the torque converter to flexplate bolts. reattach the fluif lines and crossmember bolts, and put the driveshaft back in. Start it up and see if everything is OK. Job done.

 

[Phill]

I would recommend a FSM(factory service manual), not a chilton. i pulled the trany on my 79 in my garage while on jack stands. it was quit a big job but with the help of the service manual and a friend it wasnt all that hard. but dont get me wrong its a big job to do. a transmission jack isnt a must but itll make it a bit easier.

 

[dmdodd]

Thanks for all the comments and advice.

I do indeed have an AIM, however I've always found it very hard to navigate, and very counter-intuitive to find specific parts.
I did find diagrams on p384 of the underpan, and how the 4 bolts need torquing to 8-12 N.m (~6-9 ft.lbs).
On p364 I found the flexplate-to-converter torque values as 40-54 N.m (~30-40 ft.lbs)
Annoyingly however the AIM shows the engine coming already 'pre-assembled' with the flexplate attached, and therefore no where can I find the torque values needed. Anyone know what values these should be?

I do have a Chiltons, but indeed, that's fairly cr*p too.
Looks like I need to invest in the shop/factory manual on CD me thinks.
Good to hear I might not need the tranny jack, saves a few cents!

 

[Crimson Thunder]

I hate to suggest this because i know we all like to work on our Vettes,but call some transmission shops and ask how much they charge to replace your flexplate.A competent mechanic with a lift and tools could probably tackle the job in two hours.The labor cost might offset the time it would take you to do it.

 

[dmdodd]

Yeah, took the underpan and starter motor off today and indeed, the flexplate teeth are all screwed and worn.
So it's going to be a big job. Will get some quotes from the local corvette mechanics and make a choice - as it will be fairly major undertaking.

Thanks again for all the advice.
~Dan

 

[TJay]

dmdodd,
To someone with limited skills which I'm not saying you have. This is not a hard or confusing job to complete, just alot of bull work and balancing to get the tranny out and back in. Ask a friend to help as it's much easier with 2 people. Get the car on 4 jack stands, (3 ton min. bigger the better) use a trolly jack under the tranny to slide it back, down and out from under the car, it's easier to balance and handle. Once the tranny is out of your way, your looking at the flex plate and thats the easy part to change it. You would be wise also to support the motor, as it will want to tilt toward the rear once the crossmember is removed. It's only support will be the motor mounts at this point.
Good luck which ever way you decide to tackle it.

 

[chevy50]

Just my 2 cents worth,I had an old truck with a bad flexplate but couldn't find anybody to replace it for me.I read somewhere about a neat trick,get about 4 pieces of all-thread the same size of the bolts that hold the trans to the engine and replace the bolts with the all-thread as you take them out.Once done,just slide the trans back far enough to get your hand in to get to the bolts.Once done I had to use a set of small rope blocks to get it back in place,no one to help me,but all the bolt went back in without any trouble.One thing I did forget was lock tite on the new flex plate bolts and torqure converter bolts.

 

[TimAT]

Not a bad job. Not a "quick and easy" but not bad either.

You really need the factory service manual for the torque specs. The AIM won't show you the flexplate to flywheel torque. And the FSM will also have instructions for pulling the trans. It's a doable thing with a floor jack. I have a plate that I mount on the jack's pad so the trans has a little more support under the pan and is a bit more secure.
Chevy50's idea is good too- just remember to pull the distributor cap before you lower the back of the trans. And the bolts are 3/8 USS thread BTW.

 

[Curtis]

torque flex plate attaching bolts to 60 with medium locktite.. same as a flywheel.