L98 in 735i update, and need-

[htrdbmr]

The car is done, on the road, all is well. But- The 4.27 rear is waaaay to short for every day driving, and the 700R4 trans just doesn't know what to make of it. I'm in top gear almost instantly, and can't get a downshift above 35 or 40 MPH. Does any one here know where I can get a 3.64 rear for a 7 series ?

[sausrigging]

educate me on what an l98 is.

[rao]

It is the motor before the LT1. Fuel injected, cast iron block.

[LeMansGT]

I would want more like a 3.31 for a L98. Lots of tq but no rpm

[htrdbmr]

What car had a 3.31, and would it fit a '92 735?

[Captain Morgan]

What car had a 3.31, and would it fit a '92 735?

its a popular (older) GM gear ratio, the common rear diff in GM these days is 3.42 and would probably make your 700R4 a bit happier, as well as your wallet.

Not sure what kinda rear the 7-Series came with, but Im sure with a little welding and creativity, you could make many diffs fit in there.

[LeMansGT]

its a popular (older) GM gear ratio, the common rear diff in GM these days is 3.42 and would probably make your 700R4 a bit happier, as well as your wallet.

Not sure what kinda rear the 7-Series came with, but Im sure with a little welding and creativity, you could make many diffs fit in there.

I am not sure about BMW ratios as I come from a Corvette back ground. I would not go any numerically higher than a 3.42 if possible otherwise I would look into a TPIS miniram to extend the power band on the L98.

[htrdbmr]

I didn't think you could still get the old TPIS stuff, but it would certainly help the motor, as it is a 383. Since you're a 'vette guy, what was the factory gear in a '91 L98 vette?

[Captain Morgan]

I didn't think you could still get the old TPIS stuff, but it would certainly help the motor, as it is a 383. Since you're a 'vette guy, what was the factory gear in a '91 L98 vette?

there were 4 gear ratios for the vette in '91
2.59
3.45
2.73
3.07

3.07 seems to be the most common rear and was available with the L98, usually with Automatics. The 2.59 gear seems to be with Autos as well, so i can only assume the 2.73 is the standard 6-speed ratio and the 3.45 was optional, but thats just my guess, dont quote me on that :D

[Rob Levinson]

BMW large gearset size 3.64 is available (in fact, I've got one in my M5).

The E46 M3 uses the 3.64/3.62 (gearset varies slightly by BMW OE parts supplier) and should be easy to find used given how many M3 owners switch to a 3.91 or 4.10.

If memory serves me, you may get lucky and find one in a 1982 733i.

[MWrench]

3.64 large gear set is also standard in the E31 850Ci w/auto box, and the E32 750 after 7/90 chances are it will not be LS (a few were made but it is rare) but at least it is the ratio you want and large gear set. It will bolt into the E32 735 but you may have to shorten the driveline a bit, the 6 cylinder diff is shorter then the V-12 diff.

HTH

[htrdbmr]

Thanks for your responces, I've since found out that almost all the 5 series rears fit, and 3.46, 3.64, 3.73 are available.

[Rob Levinson]

Thanks for your responces, I've since found out that almost all the 5 series rears fit, and 3.46, 3.64, 3.73 are available.

E34 only! E39 (not incl M5) uses a different gearset type.

- Rob

[scabzzzz]

Would diffsonline.com not provide something that is rebuild and or custom and ready to drop in?

[LeMansGT]

there were 4 gear ratios for the vette in '91
2.59
3.45
2.73
3.07

3.07 seems to be the most common rear and was available with the L98, usually with Automatics. The 2.59 gear seems to be with Autos as well, so i can only assume the 2.73 is the standard 6-speed ratio and the 3.45 was optional, but thats just my guess, dont quote me on that :D

I think the 6 speeds were 3.31 or 3.54 for the L98s. All LT1/LT4/LT5 (Zr1) 6 speeds were 3.45s. The ZF in the C4 and the T56 in C5s as well as other vehicles were all double overdrives. The ZF was a 0.50 6th.

http://www.corvetteactioncenter.com/specs/c4/1989/89prod.html

[LeMansGT]

I didn't think you could still get the old TPIS stuff, but it would certainly help the motor, as it is a 383. Since you're a 'vette guy, what was the factory gear in a '91 L98 vette?

http://www.tpis.com still has it listed. I don't know if you can get it for sure or not. Accell had another intake. Thirdgen.org used to have some good info on the L98s. I have not looked into building these motors in a long time. A ZZ9 or LPE 211/219 cam and a TPIS mini ram with a 3.64 gear in a 7 series would be :evil2 A LT1 intake might be another option http://www.lt1intake.com/

[Fast 7]

Thanks for your responces, I've since found out that almost all the 5 series rears fit, and 3.46, 3.64, 3.73 are available.

I've got a 3.73 diff out of a 1980 745 if yo uare interested.

[Fast 7]

http://www.tpis.com still has it listed. I don't know if you can get it for sure or not. Accell had another intake. Thirdgen.org used to have some good info on the L98s. I have not looked into building these motors in a long time. A ZZ9 or LPE 211/219 cam and a TPIS mini ram with a 3.64 gear in a 7 series would be :evil2 A LT1 intake might be another option http://www.lt1intake.com/
Can't use a LT1 intake on a l98 motor. Lt1 have opti spark and has no hole for a distibuter so this won't work. L98's are the old style blocks and the only in take upgrade he ca use is an aftermarket tpi intake, like a ram jet. Which really wouldn't do much because you can buy bigger intake runners for hte TPI motors from SLP and biggger throttle bodies.

[rao]

That's exactly what www.lt1intake.com is all about, using LT1 intakes on SBC blocks with an accommodation for a traditional distributor.

[Fast 7]

I just don't think the gain will be worth the expense.

[rao]

I just don't think the gain will be worth the expense.

That is probably true if the motor already has TPI.

[LeMansGT]

Can't use a LT1 intake on a l98 motor. Lt1 have opti spark and has no hole for a distibuter so this won't work. L98's are the old style blocks and the only in take upgrade he ca use is an aftermarket tpi intake, like a ram jet. Which really wouldn't do much because you can buy bigger intake runners for hte TPI motors from SLP and biggger throttle bodies.

The bigger runner helps power but another problem with the L98 intake is the runner length is so long which helps tq but kills hp. Every complete aftermarket intake I know of has shortened the runner length. The Lt1 maybe a cheaper option than a TPIS mini ram or Accell Superram.

It all depends on your goals. I would research any changes on the f-body and Corvette boards.

[htrdbmr]

The modified LT1 is much cheaper than the mini-ram, or accel "pizza box" For now, I'm digging the torque an L98 383 makes.

[moorepwr]

Use the Holley Stealth Ram if you have room under the hood. Better than the original L98 intake, way cheaper than the TPiS MiniRam, and not a jacked-up attempt at fitting a square peg in a round hole like the LT1 intake conversion