915 Transmission with a Turbo car. Will it work?

[kevinw]

I am considering purchasing a turbo car with K27 turbo upgrade with a 3.3 litre engine. It has been upgraded to a 915 5 speed and am getting mixed answers about whether the tranny is strong enough. Any input would be appreciated

[dtw]

The 930 used the original iteration of the G50 trans, which is a real heavy brick of a unit. It is engineered to deal with that power, and had to compromise heavy engineering for cogs. (They only had 4 forward gears which is why many switched to the weaker 915).

I would be wary of a stock 915 in a turbo application, especially one whose power had been uprated. However, if the 915 has been strengthened to deal with the power, it may be a good setup.

Usually stronger differential cover plates are installed to help cope with sudden on-boost conditions. Transmission coolers are also installed; from simpler setups like the Euro 915 setup to custom jobs with individual gear squirters. There are other miscellaneous mods that be done to the guts to beef things up too. Check for receipts on any of this work. If none exist, my opinion is "run away"

-d

------------------
Dave
1972 911T (E motor) RSR replica project
http://members.nbci.com/dtwinters/garage/

[89911]

I have read, (I read alot about 911's), that the HP limits for a standard 915 are around 250 HP or less. Of course this figure can vary and people run substantially more. That said, I would not trust a 400HP car on it unless extensive modifications were made if possible. When the upgraded to the G50, the limits were greatly raised.

------------------
8 9 9 1 1, The last of the line.

[This message has been edited by 89911 (edited 07-08-2001).]

[RarlyL8]

I'm counting on the 915 being strong enough. That's whats going in front of my 3.3T swap in my SC.
How long the clutch and tranny last is up to you. No dragrace starts or speed shifting allowed, narrow tires are a plus.
They use these trannies with V8 conversions all the time. The turbo can't match the instant torque of a V8, which is what destroys them.
I would not call the 930 4spd to 915 5spd an "upgrade". You would have to add a later 930 5spd or a 993 6 spd for that. The advantage to swapping in a 915 is just the gearing. I spoke with a fellow some time back who did this swap. He said it was like adding 100hp to the car.

[john walker's workshop]

i've got an 81 915 box hooked to a 77 3.0 turbo with SC cams and a K27. haven't killed it yet. clutch seems to be holding out too.

[Roland Kunz]

Hallo

the 915 tranys are made in stages;
2,7 with magnesium case
2,7 RS with Oilpump
3,0 with aluminium case
3,2 with Oilpump and oilcooler

The 3,2 L unit will have enough strenght to handle a high torqe turbo for street applications. The load on the trany is a calculation from the tourqe deliverd from the engine and how much resistance come from the tires. Now if you have normal tires they will spinn if you overload them and the trany will not see all the tourqe deliverd by the engine. If you have wide tires and race sliks the story looks an other way.

All tranys will handle enourmus power but get stressed on the long run. The stock 3,2L unit will handle 300+ HP in Race cars ( lighter but wide rubber )
The magnesium case is to weak and the 3,0 will need a oilpump and oilcooler to cool down.
Those tranys where constructet and ratet to withstand race situations or full load high speed driving on the high way.

I think the R&P will withstand the turbo load the weak point are the gears.

This is the reason why Porsche made the 930 trany and it only contains four gear sets. Basically it is a beefed up 915 trany.

Now if you race you can go to straight gears witch will handle much more power. Also you can use other race stuff to push the limits.

The G50/50 came in 1989 on the turbos and are basically the 964 tranys.

Grüsse