Transmission strength

E86Z4MC · 10-14-2022, 07:08 PM

I've read that the transmission of the z4m is designed for a maximum torque output of 273 ft lb. Given that the a stock s54 outputs 269 ft lb, what is the risk of modifying the engine for more performance with respect to the transmission? Also, is this why there is a torque limiter in first gear for the ecu?

Lastly, if there was a desire to upgrade to a more robust solution, what options exist?

grannyknot · 10-14-2022, 08:21 PM

Well an awful lot of guys have boosted the power of S54's, I don't often hear about blown transmissions and that would go for the M3's G420 and the Z4M's ZF.
Not saying they can't be over powered but they are pretty stout, mostly you hear about crunchy syncros in 2nd and 3rd gear.

Michael9218 · 10-15-2022, 07:27 AM

The transmission ratings seem to be very conservative. I wouldn't worry about it. Many put far more power than that through these transmissions without issue.

PayamFSU · 10-15-2022, 12:06 PM

There is torque limiter for 1st gear?

Steeler · 10-15-2022, 12:38 PM

^^ there is that to contend with.
I am more than double the factory hp/tq on my non M.
No trans issues I am aware of.
My tuner did need to address the torque limiter as I would go into limp mode when pushing the car.
Pretty sure the non M's had the same GS6-37BZ the M's got.

pokeybritches · 10-15-2022, 03:34 PM

We have put down 400+ wtq on several supercharged setups. The factory clutch will usually slip before you have transmission damage, unless driving abusively or for extended periods at high temperatures. One forum member swapped a 2JZ into his Z4 and ran the stock 3.0si transmission for a while before it finally gave up.

Westersund · 10-16-2022, 02:18 PM

These gearboxes can take a real beating, but it all depends on how you're using it. There's guys runing turbo and around 1000 hp and get them to last. If you're still N/A I wouldn't bother changing anything except the clutch maybe if you're runing 400 hp or above.

dre99gsx · 11-20-2022, 08:32 PM

I have put over 64 racing hours on my engine/trans combo in HPDE road coarse throughout 6 years. Granted it's not a S54, it is the GS6-37BZ but on a 2JZ putting down a bit over 600whp. I am on my 2nd transmission.

The first one blew 4th gear. I've never ever launched the car - but I do abuse it.

As of the 2nd transmission, I've since installed an oil cooler with fans. I'm not sure how long this one will last, but I suspect heat could be the cause. With the 7-row cooler, I've logged 240F near the end of a 20minute sesion. I've since gone to a 10row cooler (it's the only thing I can fit). Counting down the hours.

So yes, it's a stout transmission, but I don't know about 1000whp if that's your goal. Just don't do launches. Highway pulls should be able to handle it.

10-14-2022, 07:08 PM	#1
E86Z4MC Private 49 Rep 72 Posts Drives: Z4M Coupe Join Date: Jun 2021 Location: Ohio iTrader: (0)	Transmission strength I've read that the transmission of the z4m is designed for a maximum torque output of 273 ft lb. Given that the a stock s54 outputs 269 ft lb, what is the risk of modifying the engine for more performance with respect to the transmission? Also, is this why there is a torque limiter in first gear for the ecu? Lastly, if there was a desire to upgrade to a more robust solution, what options exist?
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10-14-2022, 08:21 PM	#2
grannyknot Captain 952 Rep 781 Posts Drives: 2008 Z4M coupe Join Date: Oct 2021 Location: toronto iTrader: (0)	Well an awful lot of guys have boosted the power of S54's, I don't often hear about blown transmissions and that would go for the M3's G420 and the Z4M's ZF. Not saying they can't be over powered but they are pretty stout, mostly you hear about crunchy syncros in 2nd and 3rd gear. __________________ 2008 E86 M coupe
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10-15-2022, 07:27 AM	#3
Michael9218 Lieutenant 595 Rep 484 Posts Drives: 2007 Z4 M Coupe Join Date: Oct 2012 Location: Woodstock, GA iTrader: (0)	The transmission ratings seem to be very conservative. I wouldn't worry about it. Many put far more power than that through these transmissions without issue.
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10-15-2022, 12:06 PM	#4
PayamFSU Captain 209 Rep 919 Posts Drives: 2018 F80 ZCP YMB Join Date: Apr 2015 Location: Gainesville, FL iTrader: (3)	There is torque limiter for 1st gear? __________________ 2018 F80 ZCP 6MT YMB/SO 2015 F82 M4 6MT AW/SO - SOLD
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10-15-2022, 12:38 PM	#5
Steeler Colonel 2429 Rep 2,704 Posts Drives: Built not Bought 04 Z4 VF Join Date: Feb 2013 Location: Kitchener Ontario Canada iTrader: (2)	^^ there is that to contend with. I am more than double the factory hp/tq on my non M. No trans issues I am aware of. My tuner did need to address the torque limiter as I would go into limp mode when pushing the car. Pretty sure the non M's had the same GS6-37BZ the M's got. __________________ W2A Intercooled Vortech V3Si, custom ducting, Alpha N, 60# Bosch,2.62 pulley, multi port WMI, Severn Tuning(pokeybritches), Tial, magnaflow,SS race muffler, 42 design,3.91LSD, H&R, Hotchkis,ST coils,Konis, Megan camber arms, AKG SS, Nylon mounts, Poly bushings, Carbon interior, CF Aero.APEX Last edited by Steeler; 10-15-2022 at 02:24 PM..
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10-15-2022, 03:34 PM	#6
pokeybritches Colonel 479 Rep 2,782 Posts Drives: ESS/G-Power Z4M, VF Z4, 996tt Join Date: Sep 2009 Location: Los Angeles iTrader: (12) Garage List 2006 BMW Z4M [10.00] 2006 BMW Z4M [8.50] 2003 BMW Z4 3.0i [9.00]	We have put down 400+ wtq on several supercharged setups. The factory clutch will usually slip before you have transmission damage, unless driving abusively or for extended periods at high temperatures. One forum member swapped a 2JZ into his Z4 and ran the stock 3.0si transmission for a while before it finally gave up. __________________ VF Engineering Z4 3.0i, ESS Z4M, G-Power Z4M, 996 Turbo
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10-16-2022, 02:18 PM	#7
Westersund Captain 500 Rep 876 Posts Drives: BMW Join Date: Nov 2011 Location: Hallstahammar iTrader: (1)	These gearboxes can take a real beating, but it all depends on how you're using it. There's guys runing turbo and around 1000 hp and get them to last. If you're still N/A I wouldn't bother changing anything except the clutch maybe if you're runing 400 hp or above. __________________ BMW M2 LCI -18 \| BMW 520DA Touring M-Sport -12 \| BMW Z4 M Coupe -06 \| BMW M3 -02 \| BMW Z3 Coupe -99 \| BMW 740i/6 -96 \| BMW M5 3.8 -92 \| BMW M535i -87
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11-20-2022, 08:32 PM	#8
dre99gsx Captain 510 Rep 911 Posts Drives: 1994 Toyota Supra Join Date: Aug 2011 Location: NJ iTrader: (2)	I have put over 64 racing hours on my engine/trans combo in HPDE road coarse throughout 6 years. Granted it's not a S54, it is the GS6-37BZ but on a 2JZ putting down a bit over 600whp. I am on my 2nd transmission. The first one blew 4th gear. I've never ever launched the car - but I do abuse it. As of the 2nd transmission, I've since installed an oil cooler with fans. I'm not sure how long this one will last, but I suspect heat could be the cause. With the 7-row cooler, I've logged 240F near the end of a 20minute sesion. I've since gone to a 10row cooler (it's the only thing I can fit). Counting down the hours. So yes, it's a stout transmission, but I don't know about 1000whp if that's your goal. Just don't do launches. Highway pulls should be able to handle it. __________________ Andre - 2J into a Z4 Coupe!
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