E34 gearbox (transmission)

Transmission oil should be changed every 30,000 miles. If you're near that mileage, try changing it again.

You state that your "box is full of Redline MTL". Did you get that "crunchy" feeling when it was first installed? If so, change out the Redline and put back in regular BMW-approved tranny oil.

Brett Anderson, BMW master tech, has stated that *some* BMW trannies just don't like Redline. Changing back to BMW approved stuff made it right.

Sounds like the clutch is dragging slightly. Normally, this would be indicated by a crunch when engaging reverse, but I think this model has synchromesh on that too.

Hi, thanks for the reply.

That's interesting. You appear to be correct: the Bentley manual lists changing the oil under Inspection 2, which it states is roughly equivalent to 30,000 miles. Most cars seem to have an interval of 100,000 miles or none at all which is pretty stupid, and I've damaged enough gearboxes through hard driving on 10 year old oil so that now I always change the gear oil along with the engine oil as soon as I get a car. I've been driving this one for 3 years without it getting noisier or more difficult until last week.

I'll have done about 30k. Although Redline is supposed to have a long service life I'm going to change it, and try MT-90 (thicker stuff) this time to see what happens. I still don't understand why it seems to have gone bad suddenly but perhaps it's all the nice metal flakes floating around inside after I crunched it, or it could be something in the linkage broke or wore out. It seemed a little better today.

Incidentally the car has 155,000 miles - I should have mentioned that.

No, it was a huge improvement over whatever was in before (ATF I presume, age unknown). Previously it whined badly in 1st and even started to rattle, and the shift was less smooth.

The manual says a 520i or 525i uses SAE 80 gear oil, single grade engine oil or ATF, then contradicts itself by saying *only* use ATF in a 525i. Maybe a mistake caused through updating the book from the M20 to M50 engine, hence two different 525is being referred to.

According to the blurb from Redline, MTL has the viscous properties of ATF while protecting the components better. I first started using it in my E21s based on countless recommendations from the E21 community and, while it didn't work magic in the way some claimed, it proved useful for reducing noise and improving shifts, so I used it in the E34 too.

Yes, change your tranny and differential fluids if you have over 30K on them, you should notice a difference. I currently have Redline in my 90

Hi Dave. How are you?

Funny you should mention that. A friend of mine used to insist almost to the point of violence that it did, but I don't think it does. I'm pretty sure you can crunch reverse easily just like on any normal car, but I might delicately try it out tomorrow to be sure. I remember testing it before, though, when he told me it had a synchro. Unless it's a really, really weak synchro designed *only* to compensate for you not pausing after pressing the clutch, not allowing for the car to actually be moving?

I would have thought it was the clutch too except for it not crunching on reverse. And the not going into 1st when stationary, because wouldn't a slightly dragging clutch actually help it? I associate that problem with the gearbox randomly stopping at *just* the wrong place.

I'll see if I can work out how to change the fluid because it's past due anyway. I still have nightmares from the last time I worked on clutch hydraulics.

Fine thanks Dan. And you?

My '87 520 E28 did. Quite surprised me

Dunno. Obviously, the main use is to be able to select reverse quickly from rest.

On a car without synchro, yes. The actual teeth can stop selection if opposite one another. As did most BMC products. ;-) Ford used to have a thread on the shaft, so moving the gear to engage it turned it as well. However, synchro clutches have many more teeth and are tapered to allow easy selection, so are far less likely to baulk.

Does the pedal feel different? That would be the giveaway if it's hydraulics. Unfortunately other things can cause a clutch to drag, and can involve major surgery.

Not so bad. Have you still got your SD1 Vitesse? I love those cars.

Seems like I can't crunch it through engaging reverse quickly so you might be right about this. I'm sure it can crunch a bit if you engage while still moving, but perhaps it's a different type to the forward gears. Not a helpful innovation when you want to check the clutch!

That's a good idea. I always did like Ford gearboxes (shame about the other bits).

You're right of course, when I think about it a gearbox in good condition would simply block you going into first if you didn't press the clutch, so a slight drag could do the same.

It's hard to tell if it is dragging. If you press the clutch and quickly engage a gear you get a clunk presumably from the still-spinning input shaft being stopped abruptly. If you wait half a second it doesn't clunk. Been like that since I've had it.

No it doesn't feel different. The fluid's probably three times older than it should be so I'll attempt to change it anyway. What other things can cause clutch drag? I've had clutches apart before and can't really imagine what would do it apart from just not moving it enough (for whatever reason). Obviously rust, dirt, etc, but this car gets used every day.

I changed the gear oil tonight but haven't tested it. Even if it doesn't help much it obviously needed changing anyway, so thanks to bfd for pointing out the 30,000 mile schedule that I wasn't aware of.

Yes. Just had replacement of all damaged body panels and a full respray in the original black. Been spending most of this week fitting it up - I got a very good price on the main work so putting the trim etc back on is down to me. It's looking very good.

Well, near all synchro can be beaten if you try hard enough.

The ones they used on their '60s-70s RWD designs were superb. And IIRC, the original Cortina had the first all synchro 4 speed in the UK.

Well, with the brakes off, powerful synchro will actually make the car go forward and eventually engage the gear without using the clutch. Used to be the party piece of early Vauxhalls (GM) in the '30s - according to my father who sold them.

If it engages easily after a pause with the clutch down, I doubt it's dragging.

Problems with the first motion shaft bearing in the centre of the crankshaft. If this is partially seized, the clutch doesn't disengage it. If it's badly worn, the drive plate goes off centre and drags. The clutch driven plate splines on the first motion shaft could be rusty, etc, preventing it sliding properly. The clutch cover could be worn in such a way it doesn't release properly. And probably other reasons I can't think of now