Geared up...

[nigel911]

Thinking about dropping a 3.2 into my 72T

* Would the original (915?) gearbox be strong enough to cope or will the engine just tear it up?

* Gearing?

* Would the gearbox from the 3.2 be better and if so will the car need any modification to fit it?

All thoughts appreciated.

[n8marx]

The 3.2 came hooked up to a 915 tranny from the factory from '84 to '86. I'd say your 915, if that's actually what you have, will probably be able to handle it.

[pu911]

The 72 915 had the short R&P, these are supposedly a weak point. The 915 are good to about 400HP with proper cooling, high torque motors can be hard on them. I have a 3.5 L rsr twin plug motor with a 915 has held up just fine.
Phil

[Paul Thomas]

You tranny would bolt right up to the new motor BUT the general consensus is that the 7:31 ring and pinion wouldn't last very long with the added torque. There was a thread about this the other day.

Edit: Phil, it sounds like we have the exact same setup. what year 915 are YOU running? Mine is a euro '86 and i want to shorten the gears.

Paul

[masraum]

The 915 from your car will require the bell housing to be notched for the sensor on the flywheel. If the engine is from 84-86 then it had a 915 with the notch already. If you get an engine from 87-89 then it had a G50 which will be a b!tch to adapt to an earlier car requiring putting new torsion bar carriers in or cutting out the rear torsion bars and going to coilover suspension.

[Paul Thomas]

Steve,
How was the 3.2 with G-50 different from the 3.2 with 915? I would think that you would only have to start cutting if he were gonna try to use the g50.

Paul

[IROC]

Originally posted by P-THOMAS
Steve,
How was the 3.2 with G-50 different from the 3.2 with 915? I would think that you would only have to start cutting if he were gonna try to use the g50.

Paul

I think he's referring to using the G50. I've got an '88 3.2 mated to my '76 915 and everything fits fine.

One on-topic note is that many people cut two notches in their gearbox to clear the flywheel sensors, but only one notch is required. The "TDC" sensor at 12 o'clock on the flywheel engine management function and isn't needed.

Mike

[pu911]

Paul,
I don't know what year the gearbox is in my car. It has the 8:31 R&P. The gear ratio's have been shortened up. The car has been sitting in a shop all summer w/ carb problems, I'll drop you a line when it's going again I can figure out what gearing is the box. The ratios are matched very nicely to the engine.
Phil

[TimT]

I have a warmed over 3.2 coupled to a 901 box with short gears...the car is a rocket.

Im careful not to abuse 1st gear, other than that the tranny is fine, and seems to be holding up to the 270 or so hp going through it....

The 915 should fare even better.

[Jack Olsen]

A stock US 3.2 isn't exactly a torque monster. I'd guess an early 915 would handle it just fine. If you track the car or do drag-race starts, it's a different story.

[silverc4s]

My 73 has it's original 915 (rebuilt in 96), attached to a stock USA 3.2. Case notched for the DME sensors as described above, no problems in the time since rebuild.

[dd74]

Originally posted by JackOlsen
A stock US 3.2 isn't exactly a torque monster. I'd guess an early 915 would handle it just fine. If you track the car or do drag-race starts, it's a different story.

Jack just touched on something I've been curious about with the 3.2: the 3.0 has 190 lbs of torque, doesn't it? And the early 3.2 has 185 lbs of torque.

Unless I'm wrong about the numbers, shouldn't the 3.0 be the more feared culprit of the 7.3:1 r/p?