1987 740 Turbo with M46

A couple months ago I noticed that the OD was having issues disengaging after I had been driving with it engaged for more than 5 miles or so. I drained the trans fluid and filled with type F ATF, and have done so a couple more times just to clean things out (the old fluid I drained the first time looked like it had been in there for a while). I was driving on the highway the other day and had the same OD issues. I got under the car to have a look see and noticed that I have a trans fluid leak. Since I was a 2 hour drive from my tools I took it to a local shop to have them top off the fluid.

Still had the same shifting issues on the drive home. When I got home I drove the car up on ramps and checked the fluid level. I ended up putting almost half a quart of fluid in before the fluid level was up to the fill hole. Is it possible that the garage did top it off and the fluid was still that low when I checked it?

I can only think of two things that could make the fluid level lower when I checked it than when the garage did.
- the OD engaging and disengaging
- the car being tilted up on ramps instead of being lifted on a 4 point lift at the garage

I have driven the car about 150 miles since filling it so I don't think the leak is bad enough to leak .5 quart over a 2 hour drive. Just wondering if I paid this garage $20 to do nothing other than move my car from one place to another in their lot.

That post was a lot longer than I intended. Just trying to figure out if I got ripped off or not. I am about 99% sure they did not do anything, but figured I would ask you guys.

I've always run a cup or so of Slick 50 ATF additive in my M46 for the past ten years. Never had any problems w/ the OD operation or shifting. It's a little viscous so you need to dilute it a bit with ATF to pump it in. I just use an old trigger oil pump with the spout removed.

OD shuddering and occasional dropout have been happening to my 83, too. No fluid leaks, but the problem is definitely heat-related. After a good run on a warm day, the OD shudders if you get below about 45MPH. This does not happen earlier in the drive, or on cold days when things are not yet fully warmed up, and therefore the fluid has not thinned out. Low fluid level will also make it run hotter - so, same issue.

The base cause, as explained by "OD Guru" Duane Hoberg, is worn piston seals failing to hold engagement pressure when the fluid gets hot (and thin). I bought his kit of seals and improved pistons - not installed yet, tho.

Duane is not a fan of Redline's MTL (manual trans lubricant), but examining its specs I noted it holds its viscosity at higher temps better than ATF, and has a higher gear-wear rating. I noted smoother shifts and better OD performance when I changed to it on both our 240's. It's expensive, so find and repair those leaks first. MTL is not the final fix, but a good bandaid.

If you topped up the trans with the car's front end elevated, it would take more, even if showing full while level. I've done this to deliberately overfill it a little.


--
Bob (son's 81-244GL B21F-M46, dtr's 94-940 B230FD, my 83-244DL B23F-M46, 89-745(LT1 V8), 98-S90, 77MGB and four old motorcycles)

Thanks for the replies. I might look into the Duane Hoberg kit you were talking about. Where would I find that?

Going to tackle the leak asap, school and work have been eating up all of my spare time lately.

Just thought of another question. After the leak is fixed, will it cause any problems having the trans overfilled a little? I am assuming it wont since you said you have deliberately overfilled before.
--
1987 744 Turbo - M46 - 154,000 miles - mine. 1998 V70 T5 - auto - 255,000 miles - Dad's. 1997 855 - auto - 170,000 miles - Mom's. 1985 Honda V65 Sabre - mine

I'm a fan of MTL.

Not sure why you are considering overfilling the gearbox.
It should operate fine with the proper amount of fluid as prescribed by the factory.

But you may be talking about just during the fill process. I also "overfill" from above but then leave the car level with the fill plug out until it stops dripping - then reinstall the plug. That way I know the fluid is at the proper level.

I also agree that you overfilled the gearbox if you topped it up while on ramps.
All fluid should be checked when the car is level.

Don't know why I never thought of just taking the fill plug out and letting it drain while level. I'll be doing that from now on!
--
1987 744 Turbo - M46 - 154,000 miles - mine. 1998 V70 T5 - auto - 255,000 miles - Dad's. 1997 855 - auto - 170,000 miles - Mom's. 1985 Honda V65 Sabre - mine

I've found that's the easiest way.
Sure you end up throwing away some new fluid, but if you're careful, it's probably no more than a few ounces.

Its possible that as you drove the heat within the tranny built causeing pressure etc you see where im going, its also possilbe that it had to do with the driving conditions themself! i just helped a buddy drop his out and resealed the top of the tranny, the entire seal blew out big job

Whether or not you got ripped off is hard to say. Even if you did, how would you prove it?
--
FCP Groton

I'm not gonna go back to this place and try to get my $20 back. I am just not gonna ever go back to them. Just trying to figure out if there was something else I was not thinking of that could make the fluid level that low.
--
1987 744 Turbo - M46 - 154,000 miles - mine. 1998 V70 T5 - auto - 255,000 miles - Dad's. 1997 855 - auto - 170,000 miles - Mom's. 1985 Honda V65 Sabre - mine

Put some cardboard down where you park it. See if you are noticing any unusual spots while parked. It might also help locating leak. Good luck