Metal in Trans Fluid

[eacmen]

So my SMG track car with has suffered in the past from occasional 3 to 4 mis-shifts. This last event however it was way worse than previous. I dropped the trans fluid and found non-ferrous metal flakes. I am in the process of dropping the trans. It has 104k mi on it. With the past 15k being hard miles. I am hoping the mis-shifts were just compression springs that are broken.

Do you guys think I should I just be looking for a new trans or is it worth trying to save this one?

Also, please forgive the dumb question. But I dropped the trans fluid but the trans is still in gear. Can I safely shift to neutral without filling the trans fluid as long as I don't start the engine?

[sapote]

But I dropped the trans fluid but the trans is still in gear. Can I safely shift to neutral without filling the trans fluid as long as I don't start the engine?

No problem, even with engine running not too long, less than 5 minutes. Dry input shaft bearing is only to worry about if engine running too long.

Non-ferrous metal, like aluminum or brass? I don't think the box is trash, but I would replace all the detent springs, balls, sleeves, the roller pin, and it should be fine again.

[George Hill]

Are you driving in S5 or S6 and staying WOT when shifting?

When we were running the SMG trans in the endurance race car we were killing 4th gear in the transmissions. Running them in S4 and just barely lifting on the shifts greatly extended their life.

I think if you pull apart the trans and inspect all the detents and spring you are not going to find anything obvious.

I'd personally be looking for a transmission.

[sapote]

Are you driving in S5 or S6 and staying WOT when shifting?

When we were running the SMG trans in the endurance race car we were killing 4th gear in the transmissions. Running them in S4 and just barely lifting on the shifts greatly extended their life.

I think if you pull apart the trans and inspect all the detents and spring you are not going to find anything obvious.

I'd personally be looking for a transmission.

George, which 4th gear parts you think are damaged? If anything I think it might be the synchro, but OP didn’t report hearing any gear grinding noise during shift.

[eacmen]

George, which 4th gear parts you think are damaged? If anything I think it might be the synchro, but OP didn't report hearing any gear grinding noise during shift.

Actually I was getting occasional grinding going from 3 to 4.

George - usually ran S4 without lifting.

[eacmen]

With the trans out is there a way to confirm the syncros are gone?

[eacmen]

So trans is out. All the springs seem to be in good shape. I did notice that the SMG actuator had a small leak. Fork was pretty worn where the clutch slave engages it. The speed sensor was leaking fluid through the sensor but I dont think that would cause the 3->4 grind. I am thinking George is correct and the syncros are compromised.

I spoke to a shop that rebuilds these with beefier syncros. I am leery of replacing the whole box with a used one as all the ones I can find have significantly more mileage on them than mine. Their contention is that the 3/4 gearset sits in the sump of the transmission in the oil and causes the slipping. They actually recommend conventional non-synthetic ATF with regular change intervals to prevent the oil from sticking to the surface of the 3/4 synchro.

My current plan is to freshen up this box with new springs, actuator, etc. Put a thinner fluid in there (was running MT-LV). And do an event in early November to see if its any better. If not I will likely go down the path of either full pneumatic sequential, or maybe a DCT swap.

[George Hill]

or maybe a DCT swap.

Only way to do that is with an aftermarket ECU replacing the DME.

[bigjae46]

I think you can limp the gearbox along a little longer if you with a 50/50 mix of GL4 lube and a GL5 75w-140 no slip fluid. Has to be no slip or not designed for a limited slip because any friction modifier will allegedly dissolve the brass synchros. I did this and it helped but the gearbox is pretty much done. Not sure how well it works with an SMG.

I’d be cautious about rebuilding these. I believe transmission is assembled at operating temps to achieve the correct clearances. Honestly as much as it sucks, a $6k BMW reman is the best option in my opinion.

Might be worth looking at a 5 speed conversion.

[Slideways]

I think you can limp the gearbox along a little longer if you with a 50/50 mix of GL4 lube and a GL5 75w-140 no slip fluid. Has to be no slip or not designed for a limited slip because any friction modifier will allegedly dissolve the brass synchros. I did this and it helped but the gearbox is pretty much done. Not sure how well it works with an SMG.

I’d be cautious about rebuilding these. I believe transmission is assembled at operating temps to achieve the correct clearances. Honestly as much as it sucks, a $6k BMW reman is the best option in my opinion.

Might be worth looking at a 5 speed conversion.

On the rebuild front, I'm curious to see what parts/solutions Partee Racing comes up with.

[George Hill]

Honestly as much as it sucks, a $6k BMW reman is the best option in my opinion..

They aren’t $6k anymore 😭

[bigjae46]

They aren’t $6k anymore 😭

How much? I should have bought some years ago when there were $4k.

But it never hurts to reach out to a dealer. Sometimes BMWNA will have an overstock and drops the prices. There was a period of time not long ago where an S54 reman was $10k and an S65 reman was $16k.

[CrookedCommie]

My WRL buddy just switched over to a ZF 8 speed, might be worth looking into. I think it added weight vs the ZF320 swap they were running previously.

[bigjae46]

My WRL buddy just switched over to a ZF 8 speed, might be worth looking into. I think it added weight vs the ZF320 swap they were running previously.

George has an 8 speed mated to an S54. Those 8 speeds should be plentiful and dirt cheap for years to come.

[George Hill]

How much?

I looked the other day and retail was something like $18k

My WRL buddy just switched over to a ZF 8 speed, might be worth looking into. I think it added weight vs the ZF320 swap they were running previously.

Which team/car?

You could expect to add at least 100# over a race ZF320 with the 8HP.

Like the DCT there is no good way to control an 8HP with a stock DME. If you run a standalone ECU there are more options but its still an expensive swap to make reliable and even then its probably going to work well, but not "like factory."