Thread: Replacing the flexplate on a GM ZZ502/502

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Have a starter that will not mesh. Checked the flxplate and it is showing some serious flat spots. I just got a new flexplate from GM and am getting ready to install it and could use some pointers.
Engine is a ZZ502/502, tranny is a 700r4, in a 94 Yukon 4WD. I will be doing this in my garage. This is my plan, please point out any obvious errors

Drop the front and read drive shafts
Support the tranny with a floor jack and some wood
unbolt the torque converter from the flewplate (I have to turn it a little to get to all the bolts)
Unbolt the bell housing from the engine (I think it's 4 bolts, at least that's all I can see)
unbolt the tranny from the crossmember supporting it
Slide the tranny back a few inches
Remove the flexplate
Install the new one, and put everything back where it belongs.

Does this sound like it will work? I really do not want to pull the engine (I do not have a hoist) and I don't want to pay $300.00 to have someone do it for me.

What are the major pitfalls I can encounter.

The engine is fairly new, only about 2000 miles on it, the tranny is 2 months old with only about 100 miles on it. The guy I bought it from shimmed the starter out wrong and messed up the fleplate, now it eats starters, and at $129.00 a pop for the autozone gear reduction starter, eating them ius not a good thing.

any suggestions would be greatly appreciated

thanks, John

sounds good to me .but on the trans use longer bolt on the block 4 1/2 to 5 the bottom two is will let you slide it back an keep it off your head the dip tube will have to come out six bolt hold the trans on a chevy and the trans cooler lines shifter link and kick down cable have to come off. trans oil will come out of tail shaft and trans lines so watch out put the drive shaft back in to keep the oil from making a mess. shiming starter can be a pain alot of times they need to go up if you know somone with a mill it can be done or use a big file the air gap should be 0.25 some of the gear reduction starter do not fit great you will have to play with it

Originally posted by DennyW
There should be 6 bolts in the bell housing. A safety, if you have the room, is take the left and right bell housing bolts out, install 2 long bolts that will give you up to 3 inches of room. That way, you can support the trans with a jack and blocks, and let the trans slide back on the 2 long bolts. Once you get the flywheel changed (flex plate), you can bolt up the starter, and check the clearance.

ya'll making that look to easy.

I have no illusions that this will be easy. I have never attempted doing something like this will the engine still in the car, but I don't have much choice. There are two nagging problems.

1. I like to do stuff myself, no point in having a hotrod that you don't wrench on.

2. I don't have the 300+ bones just laying around to pay someone to do it for me.

I don't think there is much in the way of linkage since the tranny shifts electronicaly. How much fluid do you think will leak from the driveshafts after I drop them?

Thanks a-lot guys for the tips.

John

the tough part is getting the trans oil out of you hair .but dawn works good and it works on oily ducks quack quack

I'm in the Army, not much hair to wash it out of, however, if it gets too bad, I can just shave it off and it'l grow back in a month

Originally posted by ScjohnK
I have no illusions that this will be easy. I have never attempted doing something like this will the engine still in the car, but I don't have much choice. There are two nagging problems.

1. I like to do stuff myself, no point in having a hotrod that you don't wrench on.

2. I don't have the 300+ bones just laying around to pay someone to do it for me.

I don't think there is much in the way of linkage since the tranny shifts electronicaly. How much fluid do you think will leak from the driveshafts after I drop them?

Thanks a-lot guys for the tips.

John

i was just joking youll do ok. keep the trans about leval and if its not over full you shouldnt loose a lot. i thought they had yokes on them , if they do you wont loose nothing.

i have done 400 trans but it will be the same way how much trans oil will you lose ?? put the drive shaft back put a pan down if it is leve not much?? i do not kown it is hard to say sometimes pulling the drive shaft out can make it come out from the drawing out the drive shaft

it's a 700r4, basicly a turbo 350 with overdrive. It's also 4WD which just makes this job even more of a pain. My only experience with 4WD vehicles has been working on Hummers in the Army. Just more crap to get in my way tomorrow when I tackle this beast.

Well, it has all been going quite smoothly, only one problem. Does anyone have a suggestion as to how I can get to the top 2 bolts on the bell housing. Once I get this one tackled, the rest should be smooth sailing

A couple of the guys suggested that I put some long bolts into the 2 bottom holes on the bell housing to allow me to slide the tranny back out of the way with greater safety. Does anyone have a suggestion as to where I can find some 4-5 inch long 9/16 bolts that are long enough. i'm out here in BFE and do not have a lot of stores to get stuff from. Any idea wether auto zone or O'Rileys would have something like this? Or any suggestions of something that I could use that I would have like alternator or starter bolts? I don't want to mess up the threads in the block, so trial and error are out. I was hoping that some of you experts could enlighten me as I am as shade tree as it gets.

I got the top 2 bolts out. I actually had enough clearance between the engine and the firewall to get my hand behind it. I could not believe it, but it's true.

Also need to know what to torque the flywheel bolts to, the torque converter bolts, and the bell housing bolts once I am ready for reassembaly.

I know.... I ask a-lot, but I really do appreciate it

Thanks guys,

John

P.S. If you want to see what a ZZ502 looks like in a Yukon, check out my album

i have used two starter bolts they are 3/8 16 NC they can be grade 5 . any hardware should have them .it s is hard to get a to torque wrenche in there .' but i have a built in torque in my arm ' ha ha
i use threadlocker loctite on them crank to fly wheel 65. and conveter ??? uses threadlocker and say 45 to 50 this should give you a ideal on the torque.

I mentioned this on another thread, but it bears repeating. Be dam sure you get the flex plate in the right way! Some aftermarket ones don't have a lip,on the center hole, making it possible to put it in backwards. The right way puts the ring gear closer to the engine so the starter engages all the way.

it's not aftermarket, it's GM performance products, and they must have seen this happen a-lot too since they stamped "Engine Side" on the inside of the flexplate

Thanks,

John

What, you read directions?????