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Topic: "DUH" question. (transmission temperature) (Read 937 times) previous topic - next topic

"DUH" question. (transmission temperature)

Grand total of 1000 miles now under my belt and becoming more and more comfortable moving Alice down the road.
As the commercial goes: "I'm loving it".
So, here's the "Duh"
When do I worry about tranny temps?
Noticed it up to 200 going slow and uphill, but it goes down as soon as things level out, or I gain speed.
I gather this is normal.
When does the temps become something to worry about?



[modified topic title to be more descriptive - Michelle]
In restless dreams I walked alone.
Narrow streets of cobblestone.


'93 U225
Build 4337
'14 CRV Toad

Re: "DUH" question.

Reply #1 –
300 for an hour
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: "DUH" question.

Reply #2 –
Moby,
You say "going slow up hill".  Are you changing down or letting it do its thing??  I change down to prevent the transmission laboring and that makes the fluid flow faster.

Also remember the gear you use to go up the hill is the one you need to go down again, or lower  It will prevent overheating the fluid etc.  Then judicial use of the retarder and brakes in short bursts will keep everything under control.

Speedbird 1.
2001 U320 Build #5865
Daihatsu Rocky Toad
VW Touareg
'82 F100 Stepside
Beech' Debonair

Re: "DUH" question.

Reply #3 –
Quote from: speedbird1 –
Moby,
You say "going slow up hill".  Are you changing down or letting it do its thing??  I change down to prevent the transmission laboring and that makes the fluid flow faster.

Also remember the gear you use to go up the hill is the one you need to go down again, or lower  It will prevent overheating the fluid etc.  Then judicial use of the retarder and brakes in short bursts will keep everything under control.

Speedbird 1.
I should have said that this was in a residential area.  Truth be told, it was a little tighter than I anticipated.  That's my fault, I should have anticipated more.  Another lesson learned.
Slow climbing because of the tightness, but still decent grade.
No, I let the tranny decide where to be.
Guessing from your comment I need to be more proactive.
In restless dreams I walked alone.
Narrow streets of cobblestone.


'93 U225
Build 4337
'14 CRV Toad

Re: "DUH" question. (transmission temperature)

Reply #4 –
At low speeds, you transmission is not in "lockup" and the torque converter is slipping producing heat. Once the torque converter locks up, the temperature will come down. Typical slow non-lockup speeds will be in city traffic or steep driveways. With lockup, the transmission acts like a manual transmission and is more efficient. Check your manual for what gear and rpm is required for lockup.

I tried going up forward up our driveway with our U300. It was slow, had a lot of slippage and the temp was going past 300. Now I back up and the transmission stays cool. This is with a four speed with a tall first gear.

Attached is a transmission temperature chart showing life expectancy for a typical automatic transmission.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: "DUH" question. (transmission temperature)

Reply #5 –
Trans temp will stay pretty much close to engine temp running down the highway. Pulling hills, in traffic it will run hotter.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: "DUH" question. (transmission temperature)

Reply #6 –
Clever chart. Is it for what kind of transmission. If I understand it, if I keep the temps at my usual 190-195 the tranny will last only 100,000 miles. WHAT? ? ? Proportionally the chart is probably accurate with temps and proportionate age but I'm just blocked on the 100K thing.
Larry
1996 U295 36'
Build # 4805
Actually we sold it but just like to lurk

Re: "DUH" question. (transmission temperature)

Reply #7 –
Clever chart. Is it for what kind of transmission. If I understand it, if I keep the temps at my usual 190-195 the tranny will last only 100,000 miles. WHAT? ? ? Proportionally the chart is probably accurate with temps and proportionate age but I'm just blocked on the 100K thing.
Larry
1996 U295 36'
Build # 4805
Actually we sold it but just like to lurk

Re: "DUH" question. (transmission temperature)

Reply #8 –
Quote from: lgshoup –
Clever chart. Is it for what kind of transmission. If I understand it, if I keep the temps at my usual 190-195 the tranny will last only 100,000 miles. WHAT? ? ? Proportionally the chart is probably accurate with temps and proportionate age but I'm just blocked on the 100K thing.
This is for a typical passenger car or light truck. The Allison transmissions are very heavy duty so will last much longer. Disregarding the mileage figures on the chart, it's still excellent for showing what increasing temperatures do to transmission life.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: "DUH" question. (transmission temperature)

Reply #9 –
Moby,

Your transmission is very different than most here.  It is a 4 speed hydraulic transmission.  Most are 6 speed electronic transmissions.

About the only "defense" against high transmission temperatures in stop and go traffic is to put the transmission in neutral if stopped for more than a few seconds.  And, if temperature is too high, put it in neutral and rev engine to 1000 RPM.  Transmission temperature will quickly come down.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: "DUH" question. (transmission temperature)

Reply #10 –
Our  diesel engines and Allison automatics have transmission heat exchangers designed to act as a buffer against heat buildup in heavy traffic. Our Allison fluid temps pretty much follow the engine coolant temps in traffic only climbing a little above the engine temps most of the time. If you feel the transmission temps are elevated, Brett's advice is excellent. Just go into neutral and a fast idle will bring both the engine and tranny temps down. A freeway accident, rush hour downtown traffic or trying to get back across the border might be an example with our extreme hot weather pushing the vehicle's cooling envelope to the limits.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: "DUH" question. (transmission temperature)

Reply #11 –
Quote from: Pierce & Gaylie Stewart –

Check your manual for what gear and rpm is required for lockup.

Pierce

Manual?
Manual?
We got no stinking manual.
Very basic info manuals from FT but nothing in depth.
In restless dreams I walked alone.
Narrow streets of cobblestone.


'93 U225
Build 4337
'14 CRV Toad

Re: "DUH" question. (transmission temperature)

Reply #12 –
The U225's 4 speed Allison torque converter locks up in 3rd and 4th only.

The 6 speed Allison 3000 and 4000 series lock in 2,3,4,5, and 6.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020
 

Re: "DUH" question. (transmission temperature)

Reply #13 –
Quote from: Moby –
Manual?
Manual?
We got no stinking manual.
Very basic info manuals from FT but nothing in depth.
If you don't have the information, another member with the same year and model may be able to tell you at what speed/RPM/gear your coach goes into lockup. Many of the coaches in the 1980's did not have any lockup. Our U300 with the 4 speed Allison 746 transmission locks up part way through 2nd gear and all of 3rd and 4th. The shift into lockup is VERY noticeable and makes it seem like a 5 speed. In our case, the computer is programmed to make the shift ("ATEC" means Allison Transmission Electronic Controls).

If you watch the relationship between the speedometer and tachometer, you can visually see if you are in lockup. If the speedometer lags slightly behind the tachometer when you accelerate, you are not in lockup. If they follow each other exactly with no lag in the speedometer when you push the throttle down, then you are in lockup.

Pierce

Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)