Pulled my 5er from Zion NP in Southern UT to Pahrump, NV yesterday. Pulled the Virgin River Gorge @ 65-70 mph, EGT's between 1000 and 1200, engine temp around 200 and Tranny temp around 180. The outside air temp in the gorge was 104.

When I made Las Vegas (around 100 miles later), I noticed my tranny temp start to creep up to around 200. Light came on as I was getting ready to pull the Spring Mountain grade, so I pulled over at a fuel station near the Red Rock turnoff to let her cool off (kinda hard to do when it's 104 outside!).

Stayed there for about 30 minutes - left the engine running while in Neutral. She cooled back down to 165 and I took off up the grade. I didn't get 5 miles up the hill, when the light came on again and the temp hit 200.

I spent the next 3 hours doing the STOP and GO to get over this hill because of the tranny temp.

My question is:

How hard can I push this tranny and at what temp should I start to "back off" before worrying about damage?

OH yeah...tranny temp sensor is installed in the pan.

Thanks!

 

Typo...it's a 48RH.

 

I'm guessing the lockup torque converter clutch isn't locking up anymore. Can you still feel the TC go into lock?
Cause' if it isn't, it can sure get hot in a hurry pulling a load like that.
Maybe some of the more learned tranny experts can give you a quick GO/NoGO test to try.
48RH? What year truck is this in?

 

RH is a 47.....48's are all RE, E for electronic.

 

If it is on the 95, you have a 47RH, unless you swapped in a 3rd gen tranny. However, along with SoTexRattler, is your converter locking up yet? You really should move your temp sensor to the hot line, this way you know how hot it's getting. I've had mine up to about 255 in the hot line, and the light never came on. If I remember right, it comes on when it sees 275, but I'm not 100% sure. You don't have to worry about cold temps out there, you can just take your stock sensor out and put a resistor in there so the tranny functions properly, then put your gauge sensor in its spot. It should be 1/2" NPT. I think infidel had the resistor idea, 1k ohms seems to come to mind, but check with him to be sure. If your tranny downshifted into third, did you lock out overdrive? This would cause the converter to not lock in. Need to know what gear it was pulling in, if the TC was locked in, and if you had OD locked in or out...

 

It seems to me that these run very cool , becouse mine is under the 100 except when idling and it climbs to 100 so I would think that it would cool faster shut off and that reminds me that you should turn off the TQ when pulling heavy loads , the next thing I'ld do is add a electrical cooling fan if money is no object than a thermostat to turn it on , or a switch to turn on manualy. Its been a while scince I've look at one of those charts that tells you whats happening at what temp , but I seem to remember the fluids start to cook at 180 , but stop by a trans. shop and they'll have one on the wall .

 

Matt, if you are talking about the OEM hot oil line with the threaded hex boss for the external temp sensor, that is a 3/8"NPT female thread.

On a stock '95, did DC relocate the temp sensor internal to the pan, yet still keep the original style hot oil line with the sensor port plugged?? That'd be the best of both worlds!...Pan mounted TCC temp sensor and an easy to install hot oil line temp gauge sender.

RamBob, are you stock for a '95 or do you really have an unusually modified 3rd gen tranny?

 

'95 only has the stock sensor in the hot line.
You should be driving with OD off if the temps start to climb so the TC is locked in 3rd. If you don't and run in 4th unlocked it will heat fast.
The diesel tranny gurus say to turn the engine off for a faster cool down.

 

It's a 47RH. I sometimes have a hard time reading, let alone typing!!

ID Tag indicates a "CC Torque Converter". (???)

I was out of OD when pulling the grade, but came through the Virgin River Gorge locked in OD. I guess the difference was that I had ample time to build highway speed before climbing out of the gorge and maintained it all the way until I was back on the flats.

Coming out of Vegas it's a gradual up-hill climb until Red Rock, then it's at least 6%, so it was "warm" to start with.

With the sensor installed in the pan (current config) am I getting an accurate reading of the temp, or should I be adjusting +/- for actual?

I think I might just plan for night time travel until we get out of the summer months. It's a real cooker here in the summertime and I noticed that I wasn't the only guy spending time on the side of the road along that stretch.

Other than installing a lock switch, how would you get the TC to lock in 3rd?

 

On a 95, the tranny should lock in 3rd if you push the OD off button. If it does not lock, it will heat very quickly!

 

Quote:

With the sensor installed in the pan (current config) am I getting an accurate reading of the temp, or should I be adjusting +/- for actual?

The hot line to the cooler temp can be considerably hotter than the pan and will be the hottest temp in the system.
You would be better off to install your probe in place of the stock one in the hot line. In order for the computer to let you go into OD you must trick it into thinking the tranny temp is in the normal range by jumping across the leads to the stock sensor with a 1000 ohm resistor.
Since you saw such high temps it would be wise to change the ATF ahead of schedule as the high temps probably damaged the fluid.

 

the tranny will get really hot fast when unlocked....i think its locked otherwise ud think ur loosing alot of power and not pulling anything and that would be ur complaint...i think maybe ur fluid has gone south and needs to be completely changed it has lost its properties

 

As I don't have a GSK installed yet, I'm turning about 2250 RPM at WFO. I started up the hill with OD OFF and felt it shift into 3rd - which from what I've read on this forum, doesn't necessarily mean the TC locked. Kept her turning @ 2K and as I continued up the hill, watched my Trans temp rise until the light came on.

My guess is the fluid is definitely due for replacement - thanks everyone for your input.

I guess my next question is what can I do to/for my tranny to keep this from happening in the future?

Is a HOT tranny one of the things I can expect to have when pulling this kind of weight (10,500 dry) in this kind of climate (104 today)? I'd hate to think that the purpose of having a tranny temp gauge is to know when it's time to pull over and let her cool!!

Thanks everyone.

Bob

 

u will have to change the fluid asap anyway now that you've been running her hot for quite a while...that fluid has now become useless.....if u were in 3rd or 4th UNLOCKED pulling that up the hill your rpms would stay up there but ud be slowing down rapidly...if thats what happened to u then u were definitely unlocked...and so ur gonna have to check out that tps sensor and adjust it

 

Guys, does my memory serve me right? Doesn't the brake pedal switch have a switch contact that forces an unlock of the TC when pressed? Maybe that switch adjustment is hosed up...

K.