cshaw07

iTrader: (14)

Im going to look at an 89 GTUs today. I've had a few 1st gens but never even looked at a FC until yesterday. The body has 130k (kinda rusty) and the engine/trans has 70k. It also comes with an 86 base model rolling shell with NO RUST. The "70k engine and trans part" worries me because the NA GTUs trans has a different 5th gear than the the other NA's. I read earlier that the in a stock GTUs with the 4.30 LSD rear diff, when cruising at 80mph in 5th gear, the tach should read 3500RPM.

Question:

With a regular NA trans and a 4.30 rear diff, what rpm would I be at doing 80 in 5th gear?

Im not that sure what do divide to figure that out.

Thank you!

RXSpeed16

iTrader: (41)

I believe the gtus has a turbo 5th gear (.719 vs .697) That puts it at about 3% difference. So that would only drop engine speed by about 100 rpm. You are probably splitting hairs unless you are doing a restoration. If my numbers are wrong, you can figure it out the same way.

jerd_hambone

I wasn't aware the 5th gears were different. But you are really worrying about that too much. The difference is minimal. Very minimal.

Molotovman

iTrader: (49)

The 5th on a GTUs is different than all other models. It's a .756, and it has the 4.30 rear.
To make sure it's a GTUs look at the wheel/tire size in the door. It should say the proper wheel & tire size is 205/55/16 just like a Turbo. It also should have no sunroof, crank windows, and no rear wiper.

Good luck, they're only getting harder to find!

jerd_hambone

Learn something new every day.

cshaw07

iTrader: (14)

its a rot box. felt like the subframe was going to fall out over 50mph. thanks for the help