My E30 is 24v swapped with a M50B20 and matching gearbox. Recently, I've changed the Final Drive from 4.10 to 3.46 cuz it was getting annoying on the freeway. However, I'm getting the same 'rpm to speed ratio' with the old 4.10 diff. Is it possible my clutch is slipping? I checked the 3.46 diff manually and it took 3 turns + for 1 revolution of the axle. Car was originally a 318i.
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Clutch slip? Or something else?
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find a stretch of road, throw it in 5th, and accelerate from like 15mph up to highway speed and watch to make sure the speed and revs match in a linear fashion.
we can also do the math.
assuming the ZF trans with the 1:1 ratio 5th gear
3.46 diff
and you have stock size tires - 23.9"
you should be seeing 72mph at 3500rpm or 60mph at 2900rpm
assuming the getrag with .81:1 ratio 5th gear
3.46 diff
and you have stock size tires - 23.9"
you should be seeing 71.1mph at 2800rpm or 60mph at 2350rpm
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Originally posted by straight6pwr View Postfind a stretch of road, throw it in 5th, and accelerate from like 15mph up to highway speed and watch to make sure the speed and revs match in a linear fashion.
we can also do the math.
assuming the ZF trans with the 1:1 ratio 5th gear
3.46 diff
and you have stock size tires - 23.9"
you should be seeing 72mph at 3500rpm or 60mph at 2900rpm
assuming the getrag with .81:1 ratio 5th gear
3.46 diff
and you have stock size tires - 23.9"
you should be seeing 71.1mph at 2800rpm or 60mph at 2350rpm
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Accelerate hard under load and bring the revs up to about 5k then let off the throttle. If the RPM drops suddenly after letting off the gas, your clutch is slipping.
This procedure puts the engine through max load at its peak torque output RPM, then the tach will show you when the clutch "grabs" again.
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Originally posted by AndrewBird View PostYou would know if your clutch was slipping, it's very obvious. The RPMs will go up, but you won't go any faster, similar to spinning the tires.
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The movement of the speedo and tach changes with different gear ratios, so that is not an indicator.
Download this calculator I made and insert all the numbers for your trans, tires, etc.
Then figure out what MPH you are going at X rpm and see if it matches. Do it for a few different speeds to be more accurate. Shouldn't be hard to figure out what diff it actually is.
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Originally posted by alifsyz View PostMy E30 is 24v swapped with a M50B20 and matching gearbox. Recently, I've changed the Final Drive from 4.10 to 3.46 cuz it was getting annoying on the freeway. However, I'm getting the same 'rpm to speed ratio' with the old 4.10 diff. Is it possible my clutch is slipping? I checked the 3.46 diff manually and it took 3 turns + for 1 revolution of the axle. Car was originally a 318i.
Check the axel that came out in the same way, then you will know.
To test for Clutch slip just floor it in first, or just try to do doughnuts.OBD1 M54/M52TU swap as a M50b25
Z4 non powered steering rack fits e30
Euro e46 2005/6 320d 6mt gearbox into E30 with M20 hardy and beck 1985 327s engine
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Update!
Okay so. I finally have time to look at the car again. I tested it on the Highway to see if there is any sort of abnormalities. One thing I noticed was when I was cruising at 100kmh(rpm was at 3k and fifth gear) and floored it, the speedo will reach 120kmh just before 4k rpm and then sort of floats around there as the rpm goes higher. It doesnt seem as linear as when it is at lower speeds. Could this be an indicator of a bad clutch?
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