trans temperature downhill

[mikgills]

I have a 95 Chevy Roadtrek 210 (G30 ext) 4L80 trans. HD cooling and factory aux trans cooler.
On long uphills engine temp and trans temp climb, as expected, but on the downhill engine temp goes down while the trans oil keeps going up (2nd gear). Pulling over and reving up rpms only helps until the thermostat fan disengages. After that i have no cool down and temp remains high. I have flushed the oil coolers (2) and changed trans oil every trip but same thing keeps happening. Did not know about this before adding trans oil temp gauge. trans has gone into limp mode a couple of times before adding gauge (reason for adding gauge), No service engine light. It appears the 2nd gear even on decent increase the oil temp rather than decreases.
Any body else notice this on 4L80 trans? Fan is working as it should. What can be done to prevent the increasing temp? Any experience with this tranny running hot? (95 does not have tow/haul mode). (115K miles)

[mikgills]

Ibrjet Those are decent temperatures for grades. I hope to get mine down there or even lower.
Did you pay attention to tranny temperatures AFTER you went over the passes? Did it go down with engine temp or did it continue to increase in 2nd gear? 2nd gear downhill does not cool
down like the engine temp on my roadTrek B motorhome. Usually 3rd gear is to fast on the downhill with the weight (8600#). to much braking to keep speed in check. Im trying to determine if this heat in 2nd going downhill is normal or whether I have clutch slipping generating all this heat (in addition to T.C.) What kind of cooler is your truck equipped with?
Seems to be doing a lot better than mine. I wish I had a manual tranny!! More control.

[lbrjet]

My trucks tranny is working hard going up and down. I travel at 98 percent of my GCWR. The highest tranny temp I have seen is 204 and that was last summer going from Phoenix to Flagstaff in July. The previous high was 202 three years ago going down Vail Pass east to west in 2nd gear at 4400 RPM's. Also had a 202 last August crossing the Bighorns on rt 16 after 20 miles uphill of 5 percent grade

[mikgills]

Shadow, Yes Im inclined to believe that also. Trans temp going up on descent in 2nd gear kind off threw me a curve. I was expecting it to go down not up. Apparently T.C. friction in 2nd gear is the same ascending or descending without enough cool down time in-between. I was afraid something was slipping and burning up. Wanted to increase pressure to prevent slippage.
Ive been looking at cooler/fan plate combinations from Derale, B&M, Cool, and a few other builds. Van chassis has almost no room in the engine compartment which is already jammed full. May have to relocate a few items and make room.
Anybody tried the cooler/fan combos? How much difference did you see?

[shawdowboss]

It almost sounds like your tranny cooler isn't big enough. I'd look more into cooling power. Some mfgs HD coolers are 10-15k BTU cooling capacity.

I'd look into a 30k BTU cooler. Some examples are tru-cool max and hayden.

Added a higher BTU rated cooler and improved our cooling dramatically. Had similar issues on our unit you are having, more cooling power solved the problem.

[mikgills]

yes, I can feel the mini shift and see a 200+ rpm drop when it engages. Now that i have the tech1 diagnostic computer i can hook that up and verify T.C. function, but it feels like it works fine on the flats (I live in Florida, we have no mountains to test with).
I had the tech1 hooked up while driving the last time in the smoky mountains (hills). Part of my problem is the 350 engine is barely adequate in the mountains so Im in 2nd gear to much of the time which generates a lot of heat. Doesn't have enough torque to stay in 3rd and its reving in 2nd. (needs a gear in-between those two). I try to to keep it at peak torque but with the wide gear spacing, thats difficult to achieve.

[time2roll]

Can you tell if the torque converter is locking up when expected?

[mikgills]

Sorry for the delay (went to spam file) Answering questions: after temp gauge was installed 245 degrees (trans, engine temp is fine). Radiator has been flushed but never rodded. using IV trans oil (VI came out after this was built) going to try synthetic next change. cooler is mounted in
front of A/C condenser. Changed ATF after every trip (its no longer red and smells burned)
Going downhill I sometimes smell hot oil. I noticed fresh oil around driveshaft seal after that.
Some dripped on exhaust. Cleaned area up, no more leaking. I think it was from excessive heat.
New issue, but only because I did not have trans temp gauge before. Added the gauge because
it went into limp mode (2nd gear only) 2 times in Canadian Rockies (steep ski resort area).
Changed oil and filter immediately in next town. Ext cooler is factory 11" X 5" stacked plate.
Seems rather small but i read stacked plate type are the most efficient and are not very big.
Has H.D. 1 ton cooling option but I was told by chevy the aux cooler is the same no matter what extra cooling was ordered. that makes no sense to me. Added gauge has sender in pressure test port. Compared temp readings with GM tech 1 diagnostic computer and temp on the flats is within 5* (165-185) In the mountains tech 1 reads higher and increases and decreases faster, but sender is internal for that one. Hope i answered everyones questions. thanx Mike

[hotpepperkid]

Mine temp goes up some but it take awhile. The time I took US-550 from Silverton to Ouray I went down for Red Mt in first gear at 25 mph and it got up close to 200 but that's was several miles

[DSDP_Don]

As others have asked, you don't say what temps you are seeing. They may be normal. If I read your statement correctly, you said you pull over and try to cool it off. That may be detrimental. When you pull over, you lose air flow and will often cook the transmission, doing more damage than just continuing to drive.

You may need the radiator cleaned as stated by another and you could have a transmission that is not locking/unlocking the torque converter and causing issues. First though.....let us know what temps you're seeing and hopefully they are numbers, not a line on a cold/hot gauge.

[DinTulsa]

Is this a new issue, or has it always ran hotter than you are comfortable with? How long have you had the MH? When you change the fluid, is it burnt or still red? My thought would be to add another cooler, and keep your foot slightly on the throttle. This is just a guess, but you may not be circulating as much fluid coasting down the hill which allows your temp to creep up. You might double check the gauge as well to ensure you are getting accurate readings.

[Gene_Ginny]

I noticed that with my 4Runner going up and down the hills in Maine. Seems if I keep my foot lightly on the gas after the top of the hill the temp comes down faster that just coasting. In my case I get concerned if my ScanGauge shows 210(f).

[BarneyS]

Might be that you have a clogged radiator (21 years old). Might be time to have it rodded out or maybe even replaced.
Barney

[Lynnmor]

mileshuff wrote:
My tranny temp always seem to drop when going down hill. Possibly because I use an exhaust brake?

No, an exhaust brake will put more load on the transmission and less load on the service brakes.

[sch911]

Turtle n Peeps wrote:
How hot does it get?

Yes what do you consider hot? We test these transmission's to very high temperatures during development. Max temps can go as high as 250F on Davis Dam testing...