700R4 Information Thread

EvilGenius said:

My reverse input drum is the second style with the round feed hole.

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NickTransmissions said:

I have identified the problem!

Next step is placing that drum into the scrap bin and purchasing a new AC Delco rev input drum. Your current belleville plate, piston, return spring and clutch pack w/backing plate will all transfer over. That should solve your clearance problems and enable you to install an Alto wide red band vs the stock band.

Also, verify you dont have first design rev input clutches - those were thicker than all of the subsequent clutch designs and used a waved plate instead of a belleville plate. They were only found in the first design drums w/the steel piston.

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EvilGenius said:

I was hoping to avoid buying a new drum as this one wasn't warped noticeably and wasn't the cursed first design. Also I already have a replacement band, whichever comes in this kit here.

My old (and new) frictions measure out to .07. I have the aluminum piston.

Would you still say that my only real option is to get a new reverse input drum?

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NickTransmissions said:

You need at least .040 to be on the safe side so get it however you need to get it. Your existing drum is prob warped but even if it's not, it's an inferior design. Those drums also had a lot of variability; I have had issues with them and clearance as well in the past. You can machine a step into the backing plate on the snap ring side, if necessary but Ive never elected to do it.

I also never reuse them - all my 700R4s get a new rev input drum, wide band and vette servo. It's good practice to update those three things for longevity and reliability.

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