1990 750il gearbox heat transfer

[geelmielie]

Quick question, how much heat transfer to the passenger compartment - the area around the gear lever is normal for these cars (when driving in moderate traffic, not speeding)? This area get quite hot in my car after say 20 min drive.

Any feedback will be great.

Thanks

[shogun]

It get's quite hot there around the gear lever. Some things to check: the engine compartment and trans = drive system has a pressure cooling system, for a good cooling effect the hood seal must be good fitting, engine compartment screening under engine must be installed (often missing), also the other heat protection parts must be installed, see realoem under 750iL HEAT INSULAT./ENGINE COMPARTM.SCREENING http://www.realoem.com/bmw/enUS/show...diagId=51_7982

Visco fan/aux fan should push the cool air around the engine and then push by the transmission and come out behind the trans, if one of these parts is missing, the air will find another way out with the lowest resistance.
Nr. 7 51711969484 air guide is also important http://www.realoem.com/bmw/en/showpa...diagId=51_7982
pic https://www.ecstuning.com/b-genuine-...e/51711969484/

[TheStigg]

I found my 4hp22-EH transmission ran alot cooler when I switched it to full synthetic ATF. If it's time to change your fluid, do so in a protracted series of partial drain & fills over an extended period of time. Maybe start by draining 2 quarts & top it off with fresh synthetic ATF. Drive it a few miles and repeat. Increase to a 4 quart drain & fill next time, and repeat. If you were to change the entire volume at once, it can lead to certain death of the transmission if it has higher miles and hasn't been flushed regularly.

I wrote a simple basic program to calculate how many quarts of fresh fluid it takes to get nearly an entire fill of fresh fluid by doing partial drain & fills. It takes approx. 21 quarts to end up with 98% new fluid per the above sequence. Unfortunately it's an old 16-bit executable and no longer runs on 64-bit machines. Here's the file if you want to play around with it:

http://www.nmia.com/~dgnrg/page_12.htm

It will run on 64-bit machines if you install "DosBox"

open a session of dosbox and type the following commands:

mount c c:\old_dos\

(where "old_dos" is the folder where you copied fluidcg1.exe to)

c:

fluidcg1.exe

[shogun]

There you touch an important subject, TheStigg, I copied this:
How does heat affect transmission life?

TRANSMISSION FAILURE/TEMPERATURE CHART

Most automatic transmissions fail due to a breakdown of the transmission fluid (oil) caused by overheating. This chart provides a graphic display of heat's contribution to transmission failure.
heatchrt.jpg
The effect is also cumulative. Short term exposure to high heat levels (or even prolonged exposure to moderate heat) can break down the oil to the point where even very short episodes of overheating will lead to failure.

from here http://www.txchange.com/heatchrt.htm

[geelmielie]

This maybe a rookie question, but why would changing all the fluid at once damage the transmission?

[shogun]

well, my opinion is, if the transmission would go broke after changing all the fluid, it is not worth to use it anymore anyway, as the clutch packs were just still working because of the accummulated sludge and dirt which came out with the old fluid

[TheStigg]

The grey area is when doing a full flush on an automatic transmission with high miles, say more than 100k, if it has never been changed. The theory is over time, contaminants become embedded in the clutch pack friction surfaces. ATF is highly detergent. Fresh ATF, if the whole system is changed, is very aggressive and will clean the contaminants from the clutch material. The problem is it is too aggressive and can attack the old clutch material and the adhesive used to bond the clutches to the metal backing rings. If the clutch packs deteriorate due to fresh fluid, the particulates can accumulate in the valve body causing shifting problems. If the clutch packs go to crap altogether, then they will wear metal-on-metal with a failure shortly thereafter.

This is why I say only do a few partial drain & fills, so as to "acclimate" the transmission to new fluid gradually. Case in point: I have an e30 with a ZF 4hp22 automatic. It shifted funny when I first bought it at slightly over 100k miles. The fluid was old, brown instead of red, and had a slight burnt odor. I did several partial drain & fills over the course of many 100's of miles. Shifting is much improved to the point of being normal and 8 years, 50k+ miles later.

Perhaps unrelated, but I used to have a 63 Ford T-bird with 120k miles on it. The trans fluid was very old but drove & shifted fine. I changed the fluid all at once and the trans self-destructed less than 1000 miles later. I dropped the pan & changed the filter when I did the first change and there was very little debris in the pan. This was back in the days when torque converters had drain plugs so one could change all the fluid. After the trans went tits up, I dropped the pan again and it was full of over 1/2" of grey sludge.

In summary, if a trans has more than 100k miles and the fluid is old or shows no signs of ever being changed, it is best to just leave them alone.

[shogun]

I understand your point. But my way of thinking is to get the dirt out and if then the trans fails, it is anyway scrap sooner or later. When I remove the ATF pan to change the filter and clean up the valve body, that is like reading in a book about the health of the trans, smelling, black oil, particles, sometimes steel particles. Just 2 days ago an E39 driver came to my home because he had some probs with reverse. We removed the ATF pan and found about 10 large metal pieces like these in below links from the reverse clutch of the 5HP19, that happens quite often . There is now a newer 5HP19 Reverse Drum, Heavy Duty BMW, This design is .020" Thicker than the Oem Bmw Design.
http://www.cascadetransmissionparts....vydutybmw.aspx
https://www.youtube.com/watch?v=L3fD-lYHpdA
https://forum.e46fanatics.com/showthread.php?t=750714

So we closed the trans again, filled some new ATF and he is looking now for a used 5HP19 in good condition, otherwise we have to repair it. Car still drives, but reverse is not the best.