M20 transmission upgrade

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M20 transmission upgrade

Postby M20_fever » Thu Oct 31, 2013 1:17 pm

I know this topic has been discussed a lot on the forums, but I don't really like the answers most of those threads end up with...I just don't believe there isn't a better trans to put behind a built/boosted m20 than a G260. I don't really care if its a 5 or 6 speed, I just want something that shifts well and can handle the power. My current G260 has always had a problem with going into 2nd on hard launches, and I'm tired of it.

I don't want to throw another 150-200k+ mile used G260 with an unknown history in there, so I'm exploring options on other units. If the G260 weren't so stupid expensive to rebuild that would be an option, but I'm not spending $3k to end up with a stock G260, ya know? The MM boxes are an option, but again, for the cost I feel like I could get a much better gear box.

I'm open to swapping in something like a T56, but what am I going to need in terms of parts? Custom drive shaft, Custom bell housing adapter, Custom shift linkage, Custom shift lever, Custom trans brace...what else?

Other option, another BMW trans that can work with a mix of stock parts?

Bottom line, I just want a solid performance trans that will hold 600lb/ft+ of power and shift smoothly even on the hardest launches. I'm open to suggestions. Remember, this is going into a 95% track only car, so I'm not even against something with straight cut gears, manual unsprung clutch etc...comfort takes a backseat to performance.
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Re: M20 transmission upgrade

Postby Yoshi » Thu Oct 31, 2013 1:32 pm

Just for drivetrain shock, I'd dissuade you from unsprung clutches.

The ZF transmissions are known to handle and start breaking around 650whp. A built T56 would do the job and would probably be cheaper though. You'd need a custom drive shaft. Hopefully with some kind of a slip joint so you don't have to remove the rear subframe when taking it in and out.
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Re: M20 transmission upgrade

Postby M20_fever » Thu Oct 31, 2013 1:42 pm

yeah T56 is where I'm leaning at the moment. Will I ever make 600+whp? Don't know, probably not, but I want my driveline to have a factor of saftey that will allow it to be reliable. Definitely needs a slip yoke, but its all the other parts like bell housing adapter, shifter, linkage, clutch that seem like it could get too costly...
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Re: M20 transmission upgrade

Postby Yoshi » Thu Oct 31, 2013 2:34 pm

Yea. A ZF would bold up and you could maybe use the same drive shaft. I put 500whp through mine ok.
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Re: M20 transmission upgrade

Postby M20_fever » Thu Oct 31, 2013 2:54 pm

What drive shaft did you use? I would need to bend the shift lever to use the ZF right? Does that cause the shift pattern to be goofy?
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Re: M20 transmission upgrade

Postby ten2doyle102 » Thu Oct 31, 2013 2:55 pm

I thought your trans was fine? I didn't have any issues getting it into second at all. I know you have the Shift Knob syndrome though... lol

Does it grind occasionally?
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Re: M20 transmission upgrade

Postby M20_fever » Thu Oct 31, 2013 4:31 pm

Nah, if you run it up to or just under redline in 1st 2nd just won't be there. That's what happened the first time the shifter came off for me that day, it just wouldn't go into 2nd. Its always been like that, and I've tried everything short of rebuilding the trans to fix it, I'm done. In most cases its fine, but if I really launch at 100% it will lose 2nd every time. I've done research and found others who have the same issue with g260s, and never found a fix for it. Now that I'm actively working on installing the supercharger I need to get this resolved.
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Re: M20 transmission upgrade

Postby Yoshi » Thu Oct 31, 2013 4:40 pm

The swap requires a large guibo E30 drive shaft. eta or M3 ones work. That or swap out the output shaft from the transmissions. Not sure if they hot swap though. In my experience, you don't have to bend the carrier, just the shift rod. 2 min in a vice kinda thing. Although, you could be cool like me and just solid mount the shifter to the drive tunnel.
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Re: M20 transmission upgrade

Postby ten2doyle102 » Thu Oct 31, 2013 8:51 pm

Interesting. I didn't know you had that problem. To bad I am of no help in this department though... :(
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Re: M20 transmission upgrade

Postby M20_fever » Thu Oct 31, 2013 9:11 pm

yeah, it's been an annoyance for a long time, but if I triple the HP/TQ its going to be a bigger issue...

Yoshi, I'll look into it. What shifter did you use to solid mount to the chassis?
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Re: M20 transmission upgrade

Postby Yoshi » Thu Oct 31, 2013 10:38 pm

I used a 3/8" thick plate of mild steel, drilled a hole and shoved my shifter in it. JB welded the bitch lol but it never came out. Then I bolted that to the shifter area of the sheet metal. AKG sells one for like $200. My solution was like $10. My shifter was the B&M shifter but it would work with any one.
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Re: M20 transmission upgrade

Postby M20_fever » Fri Nov 01, 2013 12:20 am

yeah I saw the AKG one, and AKG is only like 25min from my house...
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Re: M20 transmission upgrade

Postby Yoshi » Fri Nov 01, 2013 11:12 am

$200 though. WOW. I think it has lots of other options and it's a shifter too. *shrugs* not like I need it anymore. The T56 just has it there. Also, for the T56 swap, you don't know where it'll place the shifter.
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Re: M20 transmission upgrade

Postby M20_fever » Fri Nov 01, 2013 2:13 pm

yeah...I really need an option with less engineering involved right now. That and the sc install woukd be farntoo much to deal with at once.
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Re: M20 transmission upgrade

Postby Rocknrollcows » Wed Nov 06, 2013 4:09 am

why not the Catuned rebuilt trans? its relatively cheap and comes with a warranty.

http://www.catuned.com/p/59/getrag-260- ... nnApfkXSXs

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