MT tranny swap: driveshaft length questions

[infinity5]

Is there a good table or resource for figuring out which drive shaft lengths will fit with which trasnmissions in which cars? or somehting along those lines? what else back there might not fit right if you did a AT to MT swap?

my auto's been acting up and its starting to slip and i dislike automatics anyway so i thought i'd start doing some research on swapping it out. i've seen Gale's write up and a few other peoples and it doesn't seem impossible, although especially gales is sort of hard to follow for me :)

any suggestions in general? i don't have access to a lift or a pit, so this would have to happen on jackstands over the summer. think i could do it? heh :)

thanks guys

[pmlmotorsports]

a tranny swap w/o a lift ?...........Wow you are a brave man. I'm sure it COULD be done, but I think it would be making a difficult job near impossible. Btw, the MT driveshaft is a tad shorter and must be swapped along with the tranny and many other components. Good luck. You can contact these people http://www.theeurodepot.com/92535i0512.html for all the info you need in making the swap. Hope this helps.

[Jon K]

Is there a good table or resource for figuring out which drive shaft lengths will fit with which trasnmissions in which cars? or somehting along those lines? what else back there might not fit right if you did a AT to MT swap?

my auto's been acting up and its starting to slip and i dislike automatics anyway so i thought i'd start doing some research on swapping it out. i've seen Gale's write up and a few other peoples and it doesn't seem impossible, although especially gales is sort of hard to follow for me :)

any suggestions in general? i don't have access to a lift or a pit, so this would have to happen on jackstands over the summer. think i could do it? heh :)

thanks guys

All you need is the trans, the driveshaft, input flange to the diff, center bearing, guibo, pedal cluster, hydraulics, slave cylinder/mastercylinder, and new trans mounts. It can be done without a lift, just need tall jack stands and a couple floor jacks. I recommend dropping the exhaust from the cats back, jacking up the new trans, bolt it up but leave the rear mounts out for a little so that the driveshaft is easier to swing up. The hinged design of the shaft sucks. The splined coupling pinches REAL bad, so watch out for that, I had blood blisters in my two fingers for a couple of weeks.

[infinity5]

thanks for the link pmlmotor (i've already emailed them) and especailly thanks to jon. it doesn't seem too awful. hopfully the kind people at the euro depot can fix me up a convient little kit. i really just need to work up the courage as the money and time are pretty much there.

ah, thats what i was wondering most about, the input flange to the diff.. i'll need a new one.

what about the diff its self? will the ratio be fine? any strange and freakish tools i'll need? i don't have air tools so it'll all be good old fashioned by hand (and hammer ;)

[Jon K]

what about the diff its self? will the ratio be fine? any strange and freakish tools i'll need? i don't have air tools so it'll all be good old fashioned by hand (and hammer ;)


Well you will prob need a torx socket set i think for the removal of the transmission. You will need a 19mm slim box wrench for the driveshaft coupling bolt as i recall. you will also need some u-joints I think to undo and redo the shift linkage (redo, in your case since you have an auto). As for the diff, automatic transmissions are usually mated to higher ratio differentials since they try and use lower ratio gearing to keep strain down. For instace, a manual 330i has a 2.93 diff, but a automatic has a 3.46 or so. Not sure which car you have, I am thinking its a 530i, in which case I think you have a 3.15, which is good because a 530i (m60) has a 3.07 diff when paired with a 5 speed, so you gain that slight little edge of acceleration, but it won't be TOO noticeable.


525i M20 89-91
Automatic 4.10

525i M50 All 3.23

535i ->6/90 Automatic 3.91

535i 7/90-> Automatic 4.27

530i Automatic (M60) 3.15

So essentially, since you have an automatic, and you are reverting to 5 speed, you are basically giving yourself a performance increase by KEEPING your current diff (from automatic config). You will slightly hinder your top speed, but you gain significant acceleration!

[RobPatt]

a while back I considered a 4.27 but declined after realizing my '93 525ia already had a 3.91; not much increase at all. However your post says the M50s have a 3.23 instead of the 3.91. Ok I'm running to check my bentleys and etk/tis.... if it's got a 3.23 I may be looking for a 4.27; a seemingly well noticable acceleration gain from the little 6 m50TU. -Thanks, Rob.


Well you will prob need a torx socket set i think for the removal of the transmission. You will need a 19mm slim box wrench for the driveshaft coupling bolt as i recall. you will also need some u-joints I think to undo and redo the shift linkage (redo, in your case since you have an auto). As for the diff, automatic transmissions are usually mated to higher ratio differentials since they try and use lower ratio gearing to keep strain down. For instace, a manual 330i has a 2.93 diff, but a automatic has a 3.46 or so. Not sure which car you have, I am thinking its a 530i, in which case I think you have a 3.15, which is good because a 530i (m60) has a 3.07 diff when paired with a 5 speed, so you gain that slight little edge of acceleration, but it won't be TOO noticeable.


525i M20 89-91
Automatic 4.10

525i M50 All 3.23

535i ->6/90 Automatic 3.91

535i 7/90-> Automatic 4.27

530i Automatic (M60) 3.15

So essentially, since you have an automatic, and you are reverting to 5 speed, you are basically giving yourself a performance increase by KEEPING your current diff (from automatic config). You will slightly hinder your top speed, but you gain significant acceleration!

[Jon K]

a while back I considered a 4.27 but declined after realizing my '93 525ia already had a 3.91; not much increase at all. However your post says the M50s have a 3.23 instead of the 3.91. Ok I'm running to check my bentleys and etk/tis.... if it's got a 3.23 I may be looking for a 4.27; a seemingly well noticable acceleration gain from the little 6 m50TU. -Thanks, Rob.


Like M3s, the M50 has 3.23 diff. Since you do have a 3.23 diff, a 4.27 is ENTIRELY too short!!! Your top speed would be somewhere around 80mph. A 3.46 or 3.64 is recommended, a 3.64 being the highest you should go!

[RobPatt]

diff calculators....


Like M3s, the M50 has 3.23 diff. Since you do have a 3.23 diff, a 4.27 is ENTIRELY too short!!! Your top speed would be somewhere around 80mph. A 3.46 or 3.64 is recommended, a 3.64 being the highest you should go!