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Hello / Tranny Swap Questions

3K views 6 replies 4 participants last post by  El Presidente 
#1 ·
Hello folks! I've just signed up on this forum (after reading through 40 pages of the 3 series discussions). I'm one of the "old timers", and have had several BMWs through the past 20+years. (My personal car now is a '90 535). I also have some mechanical background, and am still an active crewman on a sports car racing team (not BMW however).

My daughter has a '95 325iA that is beginning to have some tranny issues. Since I am the "built in" maintenance department for this car also, I have been considering my options. I'd like to convert this to a 5 speed, and I have been thinking though what parts I'd need to do the conversion. I've got some idea already, but was very interested to read some of the threads from some of you who have already done this swap.

I have some specific questions that I would appreciate help on. Do all of the manual transmissions from E36 cars match up with the engine bell housing of the 2.5L engines? Specifically -- would a '97 M3 trans bolt up to the engine OK?

I know that I'll need a different ratio rear end, since the 5 speed is 1:1 in 5th, not 0.72 as the automatic is locked up. And I believe that the drive shaft length is different. The transmission control module should come out, I believe, but do I also need to swap out the ECU with one from a manual trans??

I think that I can figure out the shift linkage and clutch pedal & linkage etc., but would sincerely appreciate answers to the above, and any other comments you guys would care to offer. THANKS!!! Dick (Speedwrench)
 
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#2 ·
Speedwrench, I can't give you a direct answer to your question. I would start by ordering a Bentley manual for the car if you don't have one.

I'm in a similar situation with an 86 535i that has a bad 5 speed. I'm in the process of installing a 5 speed out of an 82 528e that was wrecked.
I have the car here to use for parts as I need them.

As I have progressed thru this conversion, I found the speed pickups on the bellhousing were different so I researched with the Bentley manual and found I could bring those over from the old tranny.

I am also the built-in maint dept. for this car (it's my girlfreinds daughters).

I would not do this conversion, auto to manual. Too big for my shoes unless you have lots of time and most important: an available parts car nearby.

Good Luck.......
 
#4 ·
Hi Guys --

Thanks for the response and for the welcome. Yes, I do already have the manual, and I'm not real concerned about doing the job. It's only that as well as being the "built in maintenance dept", I am likely also the "banker" on this one. I'm more concerned about overlooking some big expense item, and starting to go one direction, or buying the wrong parts and still not being able to finish the job. My daughter lives down on the Oregon coast, and I'm in Seattle, so it's not always easy to get the car to study over the project.

I have not been able to find in the manual or in the parts info that I have wheather there is a different ECU in a manual vs auomatic equipped car. I also have seen some differing opinions about the ability to match up a later (than '95)E36 transmission on a '95 car.

In my parts listings it shows a different length drive shaft for a 325i with manual or automatic. I don't have a listing that includes the M3 however. Don't know if the M3 manual and 325i manual are the same......

All info will be greatfully received....... Thanks!!!!
 
#5 ·
If you were to use the tranny, DS, and diff from an m3 then you wouldn't have any issues, other than a slower-than-normal 325i. The two will mat together fine. I am curious as to why you want an M tranny over a 2.5 tranny? If the car is not heavily modded, I don't see the benefit. Also, the cars ECU makes no distinction between auto and manual. All that is stored in the tranny's ECU.

Regardless, a new DS is required, and a new diff is reccomended.
 
#6 ·
Hi El Presidente --- thanks for the response! I'm afraid I don't quite understand your comment.... Could you explain why the M3 combination would be slower than a standard 325i?

My reason for suggesting the '97 M3 trans was only that I found one with low miles and it was cheaper than others were asking for their 325i versions. The car is a basic box stock, and I'm only looking for functionality and durability. I know that a 325i manual drive shaft is longer than an automatic one (1512mm vs 1275). I also know that the rear end gear ratio is lower numberically for the 325i manual vs 325i auto (I believe that manual is 3.15 vs 3.91 for auto). I don't know how the M3 parts compare...........

If I were to use the '97 M3 trans with a 325i (manual) driveshaft and rear end, doesn't this put me back to the same over-all gear ratios as it had before with the automatic?

I agree with your comment on the ECU. I found a listing today of the part numbers for a programmed ECU for 325i manual and auto, and the part numbers are the same.

Thanks for your thoughts!! Dick
 
#7 ·
The gearing in the m3 tanny and diff are different. The top speed would be increased, but acceleration would decrease. Using the m3 tranny and the auto diff would meet somewhere in the middle, but not exactly where it was before. I don't know the Ms gearing off hand so i can't check what the actual speed would be.
 
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