The car: 1991 535iA
I bought the car with a known broken transmission (4hp-22), and the symptoms according to the previous owner was that “it would not move forward in drive, but it would drive in reverse, until we tried to back it up onto a trailer. Then reverse burned out and the car had to pushed onto the trailer.” Burnt and slipping clutches.
A friend of mine was parting out an 86 or 87 535i (e28) and I confirmed the transmissions were the same. I installed the trans, found the trans fluid lines didn’t mount up properly, so I took the trans back out, and switched the plate the connects the bell housing to body of the trans, keeping the clutches from the e28 which were known to be working.
Put the trans back in, and drove it. Here’s where the problems come in.
The car now drives, but the gears seem to be acting up. Driving in D, the car starts moving fine, but it appears to be starting in second gear. When the car gets up to about 2500rpm, the car shifts downward into first gear. Yes, the rpm’s raise when it tries to shift into what should be second gear.
Same thing happens while in manual mode. The car is great to drive around with 1st selected. But if you shift the car into second gear, the rpm’s raise, and the car goes back into what appears to be first gear.
First thought was to change and clean the valve body. I did that, and installed a different speed sensor, and the problem still remains.
I checked the throttle position sensor, nothing was wrong there.
I replaced the crispy safety neutral switch, and no change.
I made sure the kickdown switch wasn’t stuck down.
I unplugged the battery for 30min, nothing.
I bought a tcu, but it did not have matching part numbers. It put the car in limp home mode. This told me that third gear does in fact work.
What are your suggestions? I don’t think the problem is within the transmission, but more likely to be outside. I can’t find an e34 with the same tcu part # locally, is it worth it to buy one on ebay in hopes that it solves the problem?
I’ve searched and searched and searched for an answer but have yet to find anything that works. Any help is appreciated.
I bought the car with a known broken transmission (4hp-22), and the symptoms according to the previous owner was that “it would not move forward in drive, but it would drive in reverse, until we tried to back it up onto a trailer. Then reverse burned out and the car had to pushed onto the trailer.” Burnt and slipping clutches.
A friend of mine was parting out an 86 or 87 535i (e28) and I confirmed the transmissions were the same. I installed the trans, found the trans fluid lines didn’t mount up properly, so I took the trans back out, and switched the plate the connects the bell housing to body of the trans, keeping the clutches from the e28 which were known to be working.
Put the trans back in, and drove it. Here’s where the problems come in.
The car now drives, but the gears seem to be acting up. Driving in D, the car starts moving fine, but it appears to be starting in second gear. When the car gets up to about 2500rpm, the car shifts downward into first gear. Yes, the rpm’s raise when it tries to shift into what should be second gear.
Same thing happens while in manual mode. The car is great to drive around with 1st selected. But if you shift the car into second gear, the rpm’s raise, and the car goes back into what appears to be first gear.
First thought was to change and clean the valve body. I did that, and installed a different speed sensor, and the problem still remains.
I checked the throttle position sensor, nothing was wrong there.
I replaced the crispy safety neutral switch, and no change.
I made sure the kickdown switch wasn’t stuck down.
I unplugged the battery for 30min, nothing.
I bought a tcu, but it did not have matching part numbers. It put the car in limp home mode. This told me that third gear does in fact work.
What are your suggestions? I don’t think the problem is within the transmission, but more likely to be outside. I can’t find an e34 with the same tcu part # locally, is it worth it to buy one on ebay in hopes that it solves the problem?
I’ve searched and searched and searched for an answer but have yet to find anything that works. Any help is appreciated.
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