1990 V8 305 RS auto. As far as we know, engine is stock. My son wants to have a 383 stroker put in early next year and now he needs a transmission. He wants the tranny he gets now to work on the future engine. So he's looked into 700-r4. Mechanic that's going to do it says it's a good swap but I'm looking for experience before he pays all this money. Will that trans work on both engines?

 

does he need a transmission today?

Yes, the 700R4 will work with a higher torque/HP engine but not in stock dress. You will need an upgraded unit be it from places like monstertransmission.com or local folks who can build it.

If you need a tranny today, and can afford it, and are 100% certain that he really is going to spend the $$$ and put in a bigger engine then go for it

If he's unsure, and his current trans is toast, then yank it, bring to a shop for a bench rebuild for about $350-$450 (assuming you don't need a mechanic to remove a trans and replace and refill 12 quarts of fluid)

 

Yes he will need a tranny now. It has a huge delay going into 3rd.

 

The current transmission should be a 700 R4 they just renamed it to the 4L60 in 1990 due to the horrible reputation the 700r4 earned in the mid 80's. How good a used 700r4 is depends on several factors. Year or revision of the transmission. Anything pre 1985 will be problematic unless it was updated. The other factor is how it was configured. A 700r4 out of a Corvette will have more clutchs and more planetary gears. It could have other upgrades like a better shell and strong servo springs. The other end of the spectrum would be the 700r4 build for a carbed 1986 305 out of a Malibu.

As stated above no stock trans from that era will hold up to a decent 383. Even the Vet trans would not last long against a 383. It may last longer then the really weak rear GM put in those cars

 

I did not even touch upon what Gorn said about the rear end. I guess you could just use skinny tires which never hook. I recall before I started to trailer my drag car that it had no issues on the street. On my second run of the evening it hooked well. Thankfully, my friend had a trailer and I did not live far from the track.

Unless he is absolutely sure that he is going to spend the $thousands to upgrade the engine, then just get rebuilt what you have. If he can't do the work himself, then add money to the budget of remove/replace trans and the same when it's engine time