5HP18 Automatic shifting/kickdown issue

[Noahe36]

Hi, I have a E36 323i auto with the 5hp18 gearbox, recently while going up a hill i used the kick down feature and all was working before my speed stopped increasing as quick as usual yet the revs kept increasing to around 3.5 to 4k.

After this the car was unable to change above what I assume is 2nd/3rd gear as it will struggle to get higher than 40 miles an hour while still revving extremely high.

The car still attempts to perform a gear kickdown by increasing the revs however it doesn't feel like the car is extending to reach the gear, the car speed keeps increasing albeit slowly as if it's still in the same gear.

I've drained the transmission fluid and changed the filter however this had little to no effect on the issue.

Any help on this issue would be greatly appreciated.

[Eric93se]

How dark was the fluid? Did you use a good DIY to do the job, and fill the level correctly. Some people think to put the same amount of as what came out but this is bad in practice.

If the fluid level is correct then what your describing is worn clutch discs and it would need a rebuild.

[Noahe36]

The fluid was fairly dark however it didn't look especially bad from what I could tell, there was no signs of metal or anything else, I refilled when it was warm until it started pouring out of the fill hole.

I also forgot to add a quite important detail that since then all gear shifts have been quite heavily delayed so e.g from 1 to 2 takes much longer than it used too.

[Eric93se]

You followed a guide to do the job? The car was raised level? I don't have that trans so I don't know how the job differs. You filled, went through the gears, topped off, let it warm up, checked the level again.

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How many miles on it?

[Noahe36]

Yes I followed a guide from this forum, I made sure the car was level and as far as I can tell the job is vastly the same as on the GM gearboxes just with a different fill plug location.

It does have nearly 150k miles on it and hadn't had any previous transmission fluid changes.

[whiskychaser]

Ideally, you need someone to read the TCM fault codes for you. Maybe include the year of manufacture and town where you live in case of volunteers? Did you check and adjust the shift cable? Has it got a kickdown switch under the throttle pedal? Depending on the year, the switch may be a simple connection between pin 18 of the TCM and ground. So if the switch is stuck in the 'on' position, it is going to keep trying to shift down. A quick check with a multimeter should tell you if there is continuity across the switch.

[82eye]

sounds like the clutch packs in the trans have had it. the cheapest option is a used trans if you can source it.

[Noahe36]

I haven't done any of that I'll have a look now, I've ordered an ads to serial cable so I'm hoping to read the codes once that arrives and by shift cable do you mean the position sensor or shift lever or something else?

[Noahe36]

That's what I was thinking originally however there was no signs of wear in the oil pan so I can't see it being this

[82eye]

That's what I was thinking originally however there was no signs of wear in the oil pan so I can't see it being this


once an auto trans slips like that its over. i have family that rebuilds them. not bmw only but they work on them all. other mechanics send bmw tranmission work to them.

edit : i had my dad's e39 trans done and it still was over $3000. if we didn't have the connection the repair would have been worth more than the car value. something like $8k.

[Noahe36]

That's my issue though it doesn't feel like its slipping it just feels as if it's not even attempting to change gear, and it's never atleast audibly been grinding gears or had particularly hard shifts.

[82eye]

That's my issue though it doesn't feel like its slipping it just feels as if it's not even attempting to change gear, and it's never atleast audibly been grinding gears or had particularly hard shifts.


your only option is taking it in for diagnosis. can you manually shift from gear to gear with no issue? sometimes a speed sensor will keep it from the upshift.

edit: any abs or dsc lights on ? have you scanned the car for codes yet?

[Noahe36]

The manual shifts are still slow however quite a bit better than when in Drive mode, no lights on either. I'm waiting for my ads cable to arrive and then i'll attempt to scan it for errors and I'll look into the speed sensor also.

[whiskychaser]

Check the kickdown switch is not shorted to ground. Then, if you want to check if it is inhibited from getting higher gears, disconnect the battery then pull the TCM plug. That will put you in 4th gear and will also give you reverse. 'Trans program' will appear in the cluster and the mode lights (E D etc) will go out. You can test drive it like that and can put it back as it was by simply replacing the TCM plug and cycling the ignition.

[82eye]

The manual shifts are still slow however quite a bit better than when in Drive mode, no lights on either. I'm waiting for my ads cable to arrive and then i'll attempt to scan it for errors and I'll look into the speed sensor also.

could be a speed sensor if you can still manually shift. it should be throwing a code.

[Eric93se]

Just to let you know there is a USB INPA cable, no need for serial and ADS. The software is free in the z3 diagnostics thread, and you would also get the 20pin round adapter.

If you get it rebuilt be sure that they give you a full year warranty, do not accept less.