Power Lost

[Stewart]

Hi all,

Bit new to this forum but give it my best shot.
I have a 1991 E34 with a M50 non vanos engine. I had to replace the engine and when we did this we drained the trannie and its was jet black and smelly.
New engine runs great. Now had a few problems with ZF5hp18 tranny. There are a few variations in this with plug size I have the small bayonet so I rebuilt the guts of it using existing valve body. When cold runs and shifts ok but when hot goes into limp mode.
However since new engine went in and prior to trannie work, I seem to have lost alot of power especially at take off and acceleration. It feels like I am dragging bricks around ! and just sluggish.
It feels like you could do the quarter mile in 13 minutes rather than seconds ! In neutral the engine revs beautiful.
I have several thoughts.
1. The catalytic converters are stuffed.
2. The trannie is not right.
3. The Bosch motronics are all out of wack
I would really appreciate some input as where to start?

[Tiger]

Why did you have to change the engine in the first place?

[Stewart]

Why did you have to change the engine in the first place?

The engine had a very bad rear crank seal failure, The big end bearing was shot as it had a bad knock.
The replacement engine came out of a half cut japanese import with only 30K on it (pretty rare !)
I have had the new engine placed on a diagostic tool and comes up clean.

[whiskychaser]

A bit surprised if you have a bayonnet plug on the gearbox - I thought they had a screw cap up to 9/92. It is possible for this box to engage forward and reverse gears at the same time. This is down to a check ball issue in the valve body and is fixable. If this is the case, it will feel like someone has their foot on the brake all the time. Acceleration will be slow and you will feel what seems to be a fantastic increase in the amount of engine braking. If so, I'd suggest you dont drive it for now as you could blow the D/G clutch to bits. You did replace the filter and follow the correct procedure for filling the gearbox didnt you?

[Stewart]

A bit surprised if you have a bayonnet plug on the gearbox - I thought they had a screw cap up to 9/92. It is possible for this box to engage forward and reverse gears at the same time. This is down to a check ball issue in the valve body and is fixable. If this is the case, it will feel like someone has their foot on the brake all the time. Acceleration will be slow and you will feel what seems to be a fantastic increase in the amount of engine braking. If so, I'd suggest you dont drive it for now as you could blow the D/G clutch to bits. You did replace the filter and follow the correct procedure for filling the gearbox didnt you?

I did get a good second hand gear box that had the screw cap as thats the only type it seems available. The mechanic that did the job does have a bit of knowledge on BMW's. We took the guts out of the replacement box and rebuilt it. It also seems there is another variant in these 5HP18 boxes and thats the amount of clutch plates.

The ones in the old box were completely destroyed and stripped. The new ones were great. The torque convertor was also slightly smaller.

We used the valve body from the original box due to the bayonet fitting and wiring. This valve body was never flushed so I think you are on the right track with your comments which I appreciate.

I am going to take it down for the valve body flush and have a look at the check ball at the same time. The filter is new and the fluid levels are right.

I have the spare parts still from the other valve body.

I will post the results as this has been an exhausting process to get a great car back in good running order.

Thanks

[whiskychaser]

What car have you got? If it is a pre 9/92 525i you should have a B11 torque converter. If it is a 520i it will be a Z10. The numbers are stamped on them. There are at least a dozen variants of this box - which one have you got? If its a 525i I'd expect it to be a 1056000071 or 073 or 075, probably with a 260002114 transmission control module.
Do you mean it shifts fine when cold (but is sluggish) and when hot it goes into transprog ? If you get the TCM fault codes read, they will tell you why it is throwing transprog. Maybe do that before you remove the VB again?

[Stewart]

What car have you got? If it is a pre 9/92 525i you should have a B11 torque converter. If it is a 520i it will be a Z10. The numbers are stamped on them. There are at least a dozen variants of this box - which one have you got? If its a 525i I'd expect it to be a 1056000071 or 073 or 075, probably with a 260002114 transmission control module.
Do you mean it shifts fine when cold (but is sluggish) and when hot it goes into transprog ? If you get the TCM fault codes read, they will tell you why it is throwing transprog. Maybe do that before you remove the VB again?

The original box has the code 1056000063 on it. It is a 8/91 525i . Don't even know where the TCM is some say in the engine bay box some say kick panel some say near shift lever? When I drive it when everything cold it is sluggish but changes fine. Once it gets a hot it starts to play up. Trans program may come on when at a roundabout, feels like it does.nt know what to do or what gear its looking for.
I can dive on the Motorway in 5th gear fine at 110 /130 takes a little bit to wind it up. Soon as slow down it plays up. I suppose the best thing is stay on motorway !!!
Still hasn't got that power feeling even at 110 kph very sluggish.
When I changed the engine the trannie fluid was really bad.

[whiskychaser]

Yes the 063 is just an older version of the ones I mentioned and uses the same B11 TC. The TCM is behind the right hand floor speaker. It is clever enough not to drop you in transprog if you are going along at high speed - it will wait until you are slowing down on a slip road :-) The transprog issue could be just a speed sensor problem but as this happens when it gets warm, it could also be the temp sensor. Unfortunately, the temp sensor is part of the loom on these. Checking the TCM fault codes will point you in the right direction.
The ATF might have looked like Coke but if the box isnt slipping or dragging and it shifts OK, it may well be fine for a lot more miles

[Tiger]

I would double check the proper ATF fluid level. If you have a dipstick, then it is easy enough. If no dipstick, then follow strict manufacture instruction on how to do this.

I would then test drive the car using manual shifting... selecting 1 - 2- 3- and D to see if the car drives okay in each of the gear. You can shift the gear by yourself using the M mode and selecting your gear. If this is okay, then I would try driving the car in 3 mode Auto... this is like sport mode.

By this point, you should be able to tell if it is your transmission shifting problem or elsewhere. If the transmission shift too soon to higher gear, then it would be sluggish... this is the sign that the valve body is not functioning right.

[whiskychaser]

With this box you get 3 modes (economy, sport and winter) and you can shift from D to 432 in any of them. So the dash would read ED, SD or *D. (Some clusters read M instead of * but the function is the same) If it is stuck in M, the transmission will be short shifting as Tiger suggests. For comparison, with light to moderate acceleration on a flat road , mine would change up a gear at around 2200rpm in E and about 2600rpm in S. At what rpm does yours shift up?

I just re-read post 5 and if I understand this correctly, you installed a smaller TC than originally fitted?