540iT - Hard downshifts & delay engaging reverse

[patrm99]

Hi all - I recently bought a 1999 540iT 5-speed auto with 129k. No significant service records came with the car so I have been working my way through the car catching up on whats needed.


On a particularly hot day when the car was fully up to temperature I noticed that when slowing it was shifting slightly hard when down shifting. Also, when engaging reverse there was a momentary pause followed by a somewhat hard gear engagement. The transmission is a 5HP-24 ( 1423305 ). I have not driven the car since as I understand the continuing to drive it may make the issue worse.


My planned steps are as follows:


1) Do an ATF / filter change (Pentosin ATF 6). If this fails to fix the issue ....
2) I cay buy a used / 100k identical transmission (1423305) for $280 within driving distance.
3) Swap the valve body from the 100k transmission into the car. Re-fill with new ATF. If this fails to fix the issue ....
4) Install the 100k transmission in the car.


Any thoughts on my plan of action ? Am I wasting my time trying install a valve body from another transmission to save the effort of a transmission swap ?


Any input would be appreciated.
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[TiesTorN]

2-1 hard downshift and reverse gear delay are standart features of this car :) do some research. most of us have it (especially the hard downshift) and there is no solution. you need to get used to it. it causes no harm.

only solution is to modify the tranny cooling system and make it run cooler (like 70-80c instead of factory 100c)

[ross1]

2-1 hard downshift and reverse gear delay are standart features of this car :) do some research. most of us have it (especially the hard downshift) and there is no solution. you need to get used to it. it causes no harm.

only solution is to modify the tranny cooling system and make it run cooler (like 70-80c instead of factory 100c)
I don't know the OP's solution but this isn't normal behavior
Delayed engagement is often low fluid. Hard shifting(on late ZF equipped 6's anyway) can be attributed to a faulty MAF.
What auto transmission oil runs at less than engine coolant temps??? :banghead:
@ OP A fluid service is a good start. If the oil is really bad when you drain it do several in rapid succession to dilute the nasty stuff as much as possible. No immediate need to assume the sky is falling.

[rlordjr]

I agree. Do several drain fills with a new filter the last time. Make sure you follow the correct fill procedures.

Sent from my SM-G991U1 using Tapatalk

[ross1]

I agree. Do several drain fills with a new filter the last time. Make sure you follow the correct fill procedures.

Sent from my SM-G991U1 using Tapatalk
If the fluid is nasty the filter has already been overwhelmed. New filter first time and perhaps again if more than a few changes required.

[CPHES]

I would get ZF 5 speed fluid, not use the 6 speed. If you are going to flush and refill, use a cheaper fluid like Valvoline rhat meets bmw standards.

The pre facelift e38, e39, and the e36 used a trans cooler loop that did not use the coolant as a heat exchanger - so, yes, those transmissions run cooler. How they did it from 99 on was a downgrade.

[TiesTorN]

What auto transmission oil runs at less than engine coolant temps??? :banghead:
e39 540i transmissions up until 9/98. and other air cooled transmissions with a radiator.

I'm not gonna argue about this since it has been discussed a lot. OP can waste his money all he wants. delayed reverse engagement might get fixed but 2-1 hard downshift won't be fixed without using an external cooler.

[patrm99]

Looks you are correct about Valvoline MaxLife ATF. Seems Pentosin ATF1 is now called Pentosin ATF6, but its expensive at ~$90/gal on Amazon, but apparently is a good replacment for the original Esso (Exxon) LT71141 ATF.

Here is a letter from Valvoline MaxLife ATF claiming compatibility with Esso LT71141. Valvoline maxLife is ~$26/gal currently.

Discussed here - http://www.bimmerboard.com/forums/posts/800695#:~:text=VW%2FAudi%20transmission%20fluid%20 with,%2C%20A6%20%3D%2020%20liters

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