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Old 01-24-2014, 08:34 AM   #1
LTDScott
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M50/G260 to M50/ZF

After breaking two G260s in my crap can racer (bent shift forks, I think), I'm considering swapping to a ZF transmission because they're stronger and I found a great deal on one. My car is a bit of a mutt, so it's not always easy to find info relevant to my specific combo, and after researching I'm still not positive about what it'd take to convert over to the ZF. Here's what I've got:

-7/86 325e body
-92 M50NV from an E36
-G260 and slave cylinder from ~89 325i
-Single mass flywheel (shaved)/clutch/starter from 85 325e (scavenged from the original eta motor, after I converted from dual to single mass)
-Original 7/86 driveshaft with big (135mm) guibo
-3.73 rear end

This combo has worked great (other than breaking the G260s), so I don't want to alter the way things work if possible. From what I've read, in order to swap to the ZF trans, I'd definitely need:

-The transmission itself
-M50 pilot bearing
-Original E30 trans crossmember (I have a custom angled one for the G260 currently)

But I'm not sure about a few things.

-Throwout bearing: I *think* I can use the current '85 unit because according to my sources, pretty much every E30 and E36 uses the same one.
-Clutch slave cylinder: I'm guessing I should use an E36 slave to match the trans?
-Driveshaft: The consensus I've seen is that you normally need to swap to an E36 (328i or M3) driveshaft when going to the ZF trans. I think this is because the output flange of the ZF trans uses the big 135mm guibo, and most '87+ E30s have the small guibo. My car has the big guibo though (early '87), and according to RealOEM, the original driveshaft I have is 1483mm long and the E36 is 1492mm long. Based on that, I believe I can use my original driveshaft?

Anything I'm missing here?

In regards to my steep rear end gear, this is a track only car, and according to a calculator I have, based on the gear ratio and my tire size the car would top out at about 120 at redline in 5th, which is the maximum speed we normally hit at most tracks.

Of course, the other alternative is to just keep the 260 that's in the car now (seems to be fine, survived our last race) and buy a spare for $100, but I don't really want to do another trackside transmission swap.

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Last edited by LTDScott; 01-24-2014 at 09:09 AM.
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Old 01-24-2014, 08:43 AM   #2
Bmwdayz
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Sounds like you have it figured out. The Zf will shift a lot smoother, although the 3.73 gears will make 1-2 gear pretty useless.

Zf trans with shifter arm and selector rod
e36 clutch slave
Pilot bearing
Your drive shaft should be fine if it has the bigger guibo
Stock trans cross member
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Old 01-24-2014, 09:05 AM   #3
LTDScott
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1-2 is useless on the track anyway. With the G260, we're pretty much always in 3rd and 4th gear.

Are you saying I'll need the shifter arm and selector rod that goes with the ZF trans? I thought I could use my stock E30 stuff (after I re-bend my selector rod back straight).
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Old 01-24-2014, 09:19 AM   #4
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I just did the swap myself last week. I had to go back to the wrecking yard because the getrag shifter arm and selector rod are the wrong length.
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Old 01-24-2014, 09:30 AM   #5
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Did you start with with a 24V/G260 as well?
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Old 01-24-2014, 09:58 AM   #6
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No I didn't start with a Getrag behind my s52. I tried to use the Getrag shifter and selector rod with the ZF and it was way off center and to short. After I got the correct shifter and selector rod everything lined up
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Old 01-24-2014, 09:59 AM   #7
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The ZF's ratio spacing might work better than the Getrag's. If you never get out of 4th on track, then the Getrag's 5th is useless. The ZF would give you 3 gears in the space of the Getrag's 2.

That being said, if you're bending shift forks, you're pretty hard on the transmission.

I've heard that a 265 can be built to take decent abuse. It has the same ratios as the 260, but is about 20 lbs heavier.
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Old 01-24-2014, 10:59 AM   #8
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Im also running a G260/M50 setup in my car and my trans rattles like a can. Im going to be also looking into swapping the ZF trans into my car. I was told i can use the 89 325i driveshaft is that true?
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Old 01-24-2014, 11:22 AM   #9
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Quote:
Originally Posted by Bmwdayz View Post
No I didn't start with a Getrag behind my s52. I tried to use the Getrag shifter and selector rod with the ZF and it was way off center and to short. After I got the correct shifter and selector rod everything lined up
So you swapped from M20/G260 to S52/ZF and ran into this? Interesting, nothing I've read has ever said the E36 shifter carrier and/or selector rod had to be used if using the original E36 trans (either ZF or G250) is used in the swap. I'd be buying a trans that's already pulled from a car, so if that's the case, I'd have to buy the shifter arm and selector rod separately. Not a big deal, but something to consider.

Quote:
Originally Posted by The Dark Side of Will View Post
The ZF's ratio spacing might work better than the Getrag's. If you never get out of 4th on track, then the Getrag's 5th is useless. The ZF would give you 3 gears in the space of the Getrag's 2.

That being said, if you're bending shift forks, you're pretty hard on the transmission.
Yep, on the tracks we usually run (most frequently Buttonwillow), our car usually hits redline at the top of 4th gear of the G260 at the end of the longest straight. I suspect we'd be hitting redline in 5th with the ZF. I'm undecided as to whether this would be a good or bad thing, though. On the one hand, having 3 gears to use means the car will stay in the power band longer, but on the other hand, I don't like shifting unnecessarily. I'm mainly looking at the ZF for reliability.

I'm not positive that we bent the shift forks on the 260, but it's my best guess. On the first one, the trans got stuck in 2nd gear, and on the second, the trans would pop out of 4th gear every time. But yeah, I gotta instruct my drivers (and myself) to be gentle with the shifter.
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Old 01-24-2014, 11:55 AM   #10
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Quote:
Originally Posted by maclogos View Post
Im also running a G260/M50 setup in my car and my trans rattles like a can. Im going to be also looking into swapping the ZF trans into my car. I was told i can use the 89 325i driveshaft is that true?

The 89 325i drive shaft will work with a guibo adapter. Or you can drill out 3 of the hole on your current guibo so the zf bolts will fit(three thicker). I drilled mine out on a drill press so they were centered. I also used a 10 mm spacer because the 325i drive shaft has to be stretched in order to reach the zf.

The best thing to do is find the front section of a e36 3 series drive shaft that was mated to a zf and use the rear section of your e30 shaft and have them balanced

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Old 01-24-2014, 12:02 PM   #11
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Originally Posted by LTDScott View Post
So you swapped from M20/G260 to S52/ZF and ran into this? Interesting, nothing I've read has ever said the E36 shifter carrier and/or selector rod had to be used if using the original E36 trans (either ZF or G250) is used in the swap. I'd be buying a trans that's already pulled from a car, so if that's the case, I'd have to buy the shifter arm and selector rod separately. Not a big deal, but something to consider.



Yep, on the tracks we usually run (most frequently Buttonwillow), our car usually hits redline at the top of 4th gear of the G260 at the end of the longest straight. I suspect we'd be hitting redline in 5th with the ZF. I'm undecided as to whether this would be a good or bad thing, though. On the one hand, having 3 gears to use means the car will stay in the power band longer, but on the other hand, I don't like shifting unnecessarily. I'm mainly looking at the ZF for reliability.

I'm not positive that we bent the shift forks on the 260, but it's my best guess. On the first one, the trans got stuck in 2nd gear, and on the second, the trans would pop out of 4th gear every time. But yeah, I gotta instruct my drivers (and myself) to be gentle with the shifter.

There was only one forum that I read you have to use the e36 selector rod and shifter carrier. So I went a head an tried the 260 stuff anyways. Try it out yourself, use the getrag stuff on the zf and see what happens.

It sounds like your syncros aren't happy with the abuse your throwing at it. If it's the shift forks then thats a lot of force being applied. Was the trans fluid really old or low?
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Old 01-27-2014, 06:14 AM   #12
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Anyone else have input regarding whether a new shifter carrier and selector rod is needed? I'm giving thought to buying the ZF as a spare and only swapping it in if/when the G260 craps out, but of course I'd want to have all of the parts I'd need on hand.
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Old 01-27-2014, 08:35 AM   #13
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If you have the big guibo ETA driveshaft that will work fine.
You will need a stock e36 ZF shifter, carrier, and Selector rod and everything will bolt in perfectly there.
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Old 01-27-2014, 08:40 AM   #14
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I'm running a Z3 shifter. I assume that would fit in the E36 carrier?
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Old 01-27-2014, 09:06 AM   #15
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