The semi-Comprehensive M60b40 into E30 swap Q&A

[bmwmech1]

Is the only added complexity for the 6 speed the trans brace fab and DS fab? I saw something about severe trans tunnel modification but it seemed to be for the auto only.

This is correct^^^... The 6 speed is a significantly larger unit, both in size and weight, as I've had both on my shop floor and compared them. In all of the builds I've researched, there have been no mods necessary to the tunnel. Because of the length difference, both the trans brackets and the DS have to be custom made, but that is it, in my understanding. The nice thing about the 5 speed is it is a completely bolt-in affair, using off the shelf parts. With a lower numerical rear gear, the freeway RPM's will not be overly annoying and the increased torque from the V8 will still make the car very quick from a standstill. Final drive ratio in the 5 speed is 1:1 and the 6 speed is .83:1, IIRC. It really is a matter of preference and how much extra work one is willing to do for the 6 speed install...

Garey

[Mr Two]

Not that it matters, since he isn't looking to build a track/autocross/hpde car, but most people pick 5speed over 6speed actually to shift less :) S2k vs e30/v8 is like apples and oranges though. S2k keeps up because it keeps making hp higher and does not run out of air by 6k, and of course it's gearing was chosen for it's lack of torque.

This was vs my S52 car, that makes all it's power up top as well. I also had a buddy build a trans for his B16 powered Civic hatch for track use that only had a top speed of 115 or so. It was geared perfectly for NSS here and the car was fast as hell.

Is the only added complexity for the 6 speed the trans brace fab and DS fab? I saw something about severe trans tunnel modification but it seemed to be for the auto only.

[BruceBe]

i just like the idea of bolt-up oem stuff as opposed to custom fabbing, where applicable.

The 5-speed is a "bolt-up oem stuff" affair, with the exception of the shift linkage modifications, which are reasonable.

For racing, at a given track, we try to maintain the engine between torque peak and HP peak, and then attempt to minimize the number of shifts. This is what drives the transmission and differential gear selection. If the torque curve is relatively flat and broad, with quite a bit of separation between TQ/HP peaks, the car will tolerate and thrive on wide gearing.

Given the trade-offs associated with installation complexity, cost, and intended use, the 5-speed could be a good choice.

Best,
-Bruce

[mkcman17]

i was referring more to trans mounts and driveshaft, but you get my drift.

[Jean]

Well, both 5speed and 6speed are bolt-up :) Drive shaft should be the LEAST of your worries with this swap to tell you the truth.

[mkcman17]

it's not to say that i haven't/won't track my car, it just won't be a purpose track rat. drive-ability for me is tops, but i don't mind rowing gears either.

i just like the idea of bolt-up oem stuff as opposed to custom fabbing, where applicable.

[Jean]

It doesn't seem like the 6 speed is THAT much worse.

Assuming they are geared for the same top speed in top gear, a 6 speed car will be WAY faster than a 5 speed around a track. Gearing is awesome, and its one reason why my friends S2k keeps up as well as it does.

Not that it matters, since he isn't looking to build a track/autocross/hpde car, but most people pick 5speed over 6speed actually to shift less :) S2k vs e30/v8 is like apples and oranges though. S2k keeps up because it keeps making hp higher and does not run out of air by 6k, and of course it's gearing was chosen for it's lack of torque.

[george graves]

If you match the ends for the tranny/diff , then any good driveshaft shop should be able to do this given you take the needed dimensions.

Keyword is "good". I tried 4 local shops. Most of the mom-and-pop kind DS shops won't touch BMW shafts. The ends are joined to the tubes using friction welding at the factory. People say that places that repair semi drive shafts do the best job for less.

[Mr Two]

It doesn't seem like the 6 speed is THAT much worse.

Assuming they are geared for the same top speed in top gear, a 6 speed car will be WAY faster than a 5 speed around a track. Gearing is awesome, and its one reason why my friends S2k keeps up as well as it does.

[Jean]

If you match the ends for the tranny/diff , then any good driveshaft shop should be able to do this given you take the needed dimensions.

[mkcman17]

if i decided to keep the 6, could a stock e30 driveshaft be shortened to accommodate the longer trans?

[Jean]

Well, they are easily available :) Just not cheap.

[mkcman17]

6speed is over-priced / big / and expensive to repair..... i can see wanting one if you are building a cruiser..(why would you even do that with e30 though is beyond me lol)... you can just use 5 and a taller diff.

the exclusiveness of the 6th gear is a really lucrative incentive for me. my car is primarily more of a cruiser than a track rat, and i know i'll regret if i give up the 6 for a 5. in a practical sense you're definitely right...but since when is building cars a practical endeavor anywho? ha.

[Teaguer]

"Semi-comprehensive". Hahahaha! Classic r3v right there! :rofl:

[Jean]

6speed is over-priced / big / and expensive to repair..... i can see wanting one if you are building a cruiser..(why would you even do that with e30 though is beyond me lol)... you can just use 5 and a taller diff.