I am working on an 87 z28 that the previous owner installed a 91 305 with a 6 cylinder T5. I bought an 85 z28 parts car with a good t5 to put back in the 87. To put the 85 t5 behind the 91 305, is all I need to do is change the clutch? And will the clutch from the 85 work on the 91 flywheel,or do I need a clutch for a 91 V8?

The engine in the 87 good car has the bolt holes through the valve covers. The 85 parts car has the old style valve covers.

1. Do the flywheels from 85 to 91 interchange?
2.Will the clutch from the 85 fit on the 91 flywheel?.
3. Is there a different flywheel for 6 cylinders and v8s?

I hope this is enough information, to get an answer, Thanks, Chris

 

the flywheel in the 85 will not fit the 91 in 87 gm changed to a one piece rear main seal so all of the bolt holes moved. the clutch disk should be the same but in not positive and i am pretty sure the v6 and v8 flywheels are different. hope my little bit of info helps.

 

v6 clutch has smaller splines v8 has larger the clutch itslef is the same on v8 83-92 as far as i have come across

 

I ran into this problem last year and spent a year trying to figure out the clutch flywheel setup. I swapped an 84 305 HO (was blown) for an 87 305. We had to replace the flywheel and the clutch kit both. The clutch was the same for the T-5 the whole third gen run to my knowledge. You may end up using a 91 flywheel for the 91 motor. Just a word of warning from my experience. Make sure the flywheel fits in the bell housing. We used a 12.5 inch flywheel eventually and a 10.4 inch clutch from a fuel injected F code for a H code four brrl carb setup.

 

Someone correct me if I'm wrong but a T5 from a 6 cylinder car won't bolt up to a V8 block. In other words the T5 you currently have in your car was what came with a 305. You should fine out if the T5 you have in there now is a world class or non world class T5. I think the T5 from 85 was a NWC and would be weaker if you have a WC T5 in there now.

 

vbMike - yes, you can bolt a V6 T5 to a V8. All you have to do is unbolt the V6 bellhousing and bolt up a V8 bellhousing. Where you run into problems is with the clutch disc. The input shafts on V6 T5's have 14 splines whereas the V8 T5's have 26 splines. You end up having to use a V6 clutch or a special clutch disc from Advance Adapters to get it to work. The regular V8 flywheel and pressure plate are used.

Your right about the WC/NWC though. WC T5's started in 89.

To the OP - In order, your answers are: NO YES YES. You just need to make sure your clutch disc has the correct number of splines for your input shaft.

 

The WC-T5 was in the 88 years also. https://www.thirdgen.org/forums/tran....html:welcome:

 

Oops, missed that typo. Your right, it was 88.

 

OK, I think I have all the info I need. Obviously I have a correct flywheel and bellhousing because it does start run and drive OK.Trans wont go into first gear.

I am sure it has a 6 cyl trans in it. The guy I got it from was honest with me and told me so, and gave me a v8 T5 with the car. I know the main difference is the clutch/input splines on the trans.

By checking ebay I think I verified that the clutch kit for a v8 spans the years 85-91. So Im pretty sure the clutch from the 85 will go on the flywheel in the car.

Thanks to all, and correct me if Im wrong.I dont want to have to stop and look for parts when I start changing the trans out.

Thanks,Chris

 

All you really NEED is the clutch assuming everything else is in good shape. It should already have a V8 pressure plate. You may need to have the flywheel turned since the clutch that is in there is probably smaller than the one you will be replacing it with. I would check it over real good for grooves/scoring/ etc. That being said, while you are in there, you might as well replace the pilot bushing/bearing, throwout bearing, clutch, pressure plate, transmission fluid, and transmission mount. Might as well get as much preventive maintenance done as you can while it's apart to save you from having to take it back apart again. I know with my luck, I'd be tearing back into it in a month or so if I didn't.

 

I will check it all. The parts car with the good t-5 is supposed to have had the trans rebuilt and a new clutch kit installed recently.I drove it around and it seems good. Thanks alot. Chris