Operating temp range of E34 auto trans - 4HP22

[bmwpower]

Installed my gauges set with a 400*F VDO trans temp gauge, but it appears that the normal operating temp of my 4HP22 should be about 175*F (according to Bentley)... barely noticeable on the gauge (doh!).



These questions are:

(Q1) What's the maximum operating temp of this trans? Probably a moot point, but trying to figure out if this gauge is truely worthless for my application...ie, Bentley's normal operating temp of the trans is at idle (I think), but what is the temp when I'm driving, in traffic, going up a hill...you get the idea. If the temp varies greatly, maybe this gauge will work.

(Q2) Can I use an engine oil temp gauge for this application? They have lower upper limits.It can use the same sender I have, just not sure if the circuitry of the gauge is any different than a "trans" gauge.

[bmwpower]

Better view of "normal" temp, but not VDO:

[Binjammin]

I don't think it will matter if you use an oil temp gauge, so far as max temp? Trannies live twice as long if you cut the temp in half, and the inverse is also true, if you double the temp they live half as long. Whatever the normal range is, if you cool it off you'll be happy.

[tonyroc14]

yeathats interesting, everytime i drive my car, the shifer feels warm, like below the handle, so im wondering if my tranny is getting warm, or im low on fluids, it does shift pretty hard sometimes...time to flush the tranny

[bmwpower]

I don't think it will matter if you use an oil temp gauge, so far as max temp? Trannies live twice as long if you cut the temp in half, and the inverse is also true, if you double the temp they live half as long. Whatever the normal range is, if you cool it off you'll be happy.

I'm going to hook it up tonight and see what temps I get during real world testing.

[bmwpower]

I don't think it will matter if you use an oil temp gauge, so far as max temp? Trannies live twice as long if you cut the temp in half, and the inverse is also true, if you double the temp they live half as long. Whatever the normal range is, if you cool it off you'll be happy.

Ok. So how do I cool it? Isn't that what the radiator does?

Tranny was running maybe 187 or so by the time I got to work (1-1/2 hrs), but hard to tell for sure on the 400*F gauge.

[Binjammin]

Ok. So how do I cool it? Isn't that what the radiator does?

Tranny was running maybe 187 or so by the time I got to work (1-1/2 hrs), but hard to tell for sure on the 400*F gauge.

The radiator DOES cool the tranny, but you'll do well to add a tranny cooler. Try a B&M.

[bmwpower]

The radiator DOES cool the tranny, but you'll do well to add a tranny cooler. Try a B&M.

Hmmmm.... I wonder where I could fit it.

[Binjammin]

In front of the A/C condenser is the most popular. Good airflow, and it won't radiate enough heat to affect operation of the A/C. Most kits work with it installed there.

[bmwpower]

In front of the A/C condenser is the most popular. Good airflow, and it won't radiate enough heat to affect operation of the A/C. Most kits work with it installed there.

I think the power steering cooling lines there if I'm not mistaken. I'll poke around today and see what would fit.

[Binjammin]

I think the power steering cooling lines there if I'm not mistaken. I'll poke around today and see what would fit.

There should be enough room. If not, just mount it lower, like behind the vent/grill part in the lower fascia.

[kalevera]

Back when my 535 was an auto, I installed a flexolite cooler to replace the heat exchanger in the radiator (I wanted to install a V8 radiator). Worked fine. I mounted it behind the bumper in the lower air dam, cut the OE cooler lines and ran BMW power steering OEL to the cooler via the core support duct that's used for the power steering cooling circuit.

The cooler with install kit was around $30 new from summit. I still have the one that I used on the shelf.

[bmwpower]

OK, to and from work today the trans was running around 225*F, which I think is kinda high. That's with about 1-1/2 hours of driving each way, averaging about 80mph.

Is this too hot? Seems like just the other day, it was running about 200*F. I don't know if something's wrong or what. It was like 60*F outside today, so maybe that has something to do with it? Should ambient temperature affect the trans temp this much?

I dunno.... I wish more people has a trans gauge so I could tell what should be normal for this trans.

I do know that my rear has started to whine, so maybe that is causing the trans to work overtime.

Gonna swap the rear tonight and see what happens.

[bmwpower]

And the replacement diff is bad! Crap...
Time to find another diff and test again.