Skip to main content ↑ ↓
Topic: Transmission Oil Temp (Read 771 times) previous topic - next topic

Transmission Oil Temp

On this trip my Tran temp gauge has gone from not reading anything to oscillating uncontrollably about 200 times a minute. I checked behind the dash in hopes of a loose wire but all seem good. We drove through a ton of snow, ice, and slush so hoping something just got knocked loose. Anyone know where the sender might be on the transmission or any other ideas?
Benjie, Ashley, Zoey, Fallon, and Lake
Round Rock, TX
In search of our next monster...

Re: Transmission Oil Temp

Reply #1 –
Got to be either a loose/corroded connector (check the connectors on top of the trans from under the bed?) or the internal connection on the sender, but I don't know where it is.  You might call an Allison Distributor and ask to talk to a tech.

http://www.allisontransmission.com/locator/bing/index.jsp?country=US
Dave and Nancy
1999/2013 U270 36' Xtreme
Motorcade # 16774
2013 Subaru Outback
KD0NIM

Re: Transmission Oil Temp

Reply #2 –
Benjie,

On my 4060R transmission, the temp sensor is in on of the large hose elbows coming out of the transmission just below the output shaft to the differential.  New sensors are in stock at Instrument Exchange in Houston and possibly in Austin too.

The sensor has a male bayonet connector with the harness having the female connector.  The female connector needed crimping slightly to make a good slip-on connection.
Rudy Legett
2003 U320 4010 ISM 450 hp
2001 U320 4220 ISM 450 hp
1995 U320 M11 400 hp
1990 Granvilla 300 hp 3208T
Aqua Hot Service Houston and Southeast Texas

Re: Transmission Oil Temp

Reply #3 –
I believe the trans temp gauge on the dash gets it's info from a sender on the back side, very bottom of the transmission. It is easy to locate. Look for two large oil lines going to and returning from the oil cooler. Close to the transmission, on one of those lines, you should see a wire attached to a sender. If you were in icy/slush conditions, That wire or connection might be damaged. That gauge does not read the actual trans temp . It gives you the oil temp going to the cooler as it comes off the retarder. If you drop off a big hill at high speed, in full retard, you may see the temp rise to 275 or 300+ within seconds. I may stand corrected but as I understand the info I learned from Allison, when the retard function is activated, there is a large spool valve that blocks main trans and sump oil from going to the cooler. The oil cooler then receives only the hot oil coming off the retarder. As a result, only a small portion of oil is super heated and when the retard function is off, the retarder control opens the large spool valve allowing the much cooler trans oil to mix and then everything goes to the cooler. This why you will see that dash gauge return to normal after only a few miles. Also, if you run a Silver leaf, the trans oil temp off the diagnostic port is not the same info as the dash gauge.

Gary O
Gary O
2000 U320 4210

Re: Transmission Oil Temp

Reply #4 –
I'll get under and take a look.  I'm hoping I may have inadvertently found the issue.  While looking for the boost solenoid, I found a 4 prong connector fully unplugged from its connector.  I plugged it back in.  I'm hoping it is somehow the culprit, but won't know until I drive again.
Benjie, Ashley, Zoey, Fallon, and Lake
Round Rock, TX
In search of our next monster...

Re: Transmission Oil Temp

Reply #5 –
That happened to me driving through a rain storm in Maine this summer. Eventually the gauge stopped working altogether. While working on my radiator replacement (you don't even wanna know) I noticed the wire had come off the transmission. I plugged it back in and the next time I started the engine I noticed the transmission gauge was working again. My sensor is on the driver's side of the transmission but yours may be different... Just get on the creeper and roll around under there until you see a wire that's unplugged, you'll find it.
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: Transmission Oil Temp

Reply #6 –
Quote
RE: . While looking for the boost solenoid, I found a 4 prong connector fully unplugged from its connector

There are two relays, each with 4 prong connectors mounted on our isolator panel. One relay powers the dash AC condenser fan mounted on rear street side fiberglass panel. The other relay powers the dash AC compressor. Our coach does not have any transmission wires on the isolator panel. Putting a wire tie around relay and connector will prevent it from coming loose.

Re: Transmission Oil Temp

Reply #7 –
Barry,

I think that may be what it was. I was hoping the plug might somehow affect ground or power but in looking at the wiring diagram this evening I think it's one of the AC plugs you mentioned. Might explain why our dash AC never worked!

I'll get under the coach in the near future to look at the transmission area better and report what I find.

Best Regards,
Benjie

Benjie Zeller
(512) 587-4628
Benjie, Ashley, Zoey, Fallon, and Lake
Round Rock, TX
In search of our next monster...