tpi88camaro

iTrader: (7)

ATSG update handbook says 93-up reverse input housing that has large square feed hole cannot be used on 87-92 transmissions. Is this entirely true? What would happen if it was used in place of a housing with the .095 round hole? Thanks

Pro Built Automatics

They are wrong. In fact on the later 700R4's they used this drum and it worked better. I have installed and have hundreds of these out there with no problems. The "feed bleed system" works better with the larger feed hole in the drum. DO NOT restrict the feed hole in the aluminum piston in the reverse input drum. If there is a restrictor installed in the hole, drill it to .070" - .076". Otherwise the clutches try to come on at high rpm in 1st & 3rd gear. You will find the clutches will burn and the steels will have hundreds of "leopard marks" on them. I have seen this dozens of times. TransGo tells you to add this restrictor and they are wrong in doing that. I have told them what I have seen in tearing down transmissions over the years, but to no avail.

tpi88camaro

iTrader: (7)

Thank you for a quick response and a great explanation.

When I tore the transmission apart I noticed the reverse input housing had this large square hole in it as opposed to the small round hole it was supposed to have. The case says it's a '91 but had been rebuilt sometime before. I am curious as to what the apply piston looks like. I will post back with that info.

I have another question. Are there any identifying marks on the valve body telling you what year it is? If so, what should I look for. Thanks again.

tpi88camaro

iTrader: (7)

I finally got the time to break the reverse input drum down. It has the steel piston in it which is the 82-87E drum. It's in very good condition with only .003 wear on the outside. If I can use this drum, what mods would have to be done?

Pro Built Automatics

Since it is the early drum there is nothing to be done. The area where the band rides must be flat, not dished. Otherwise, install it as is. This drum was used 1982 - 1986. Starting in 1987 they went with the aluminum piston and the feed/bleed system. If your drum is dished, replace it with the later drum and piston. The spring assembly is the same.