Remanufactured Transmission Temp

[jabre]

I very recently had the transmission swapped on my '07 Tahoe 5.3L with 165k miles. The replacement was a remanufactured transmission and torque converter from a reputable national remanufacturer. I had it done in a local, smaller shop. I also replaced the radiator with a new OEM unit. At the time the transmission was replaced I was told by the mechanic that he blew out the lines of the old fluid and did not observe an obstruction in the lines.

Prior to the swap the transmission temp would not run above 185 unless I was towing a heavy load through the nearby hills. Even then it would barely rise above 200. Now, with the replacement transmission the temperature slowly rises up to over 205. It takes a long time to warm up to that temp, 30-45 min of city driving in Texas late summer heat. I have gotten it up to 210 at one point after driving local small hills without a load but never pushed it beyond. The engine coolant temperature hits 210 quickly and is steady at that temp so I have no reason to believe it is a radiator issue.

Fluid level is right.

What is considered normal time to reach normal transmission operating temperature?
Any suggestions to diagnose the temperature rise?

 

[Foggy]

Which transmission do you have??? 200* is pretty normal in summerish ambient temps
Wait a few weeks when the outside temps drop a bit and then it should be back
to the 175-200 range.. If it doesn't then, I'd suspect an issue with either the cooler lines
or even if the converter is not locking up when it should. When converter is locked
up properly the trans should run cool like it's supposed to

 

[jabre]

@Foggy, thanks for the reply.

The transmission is a 4L60E. I'll be patient. Just am worried about getting out too far on the vehicle and ending up driving it too hot.

I was just reading some information, per your point about the converter, is it right that putting it in trailer mode will force lock the converter? Would that help isolate by checking if it causes the operating temp to drop?

I just drove it round trip 12 miles each way almost all on the highway @ 70mpg. Trip out, 12 miles, it went from ambient/cold @ 88deg to 170deg. Sat for 15 min, engine off. Then trip back went from 170deg to 205deg. Steady rise both directions.

If it is the lines how to troubleshoot without just blindly replacing? All the the info I find is wrt to people replacing lines due to leaks. I can't find a good reference on diagnosing lines.

Thanks again for taking the time to reply.

 

[Foggy]

If you are using the proper Dexron VI fluid, 200-235 is not going to cause any issues.
You will have to do a search on the web for the "IN"/Cooled" port and the "OUT/Hot" port
at the transmission... Then do the same for the radiator lines.. Usually the upper port on
the radiator is the "in/hot" fluid while the lower port in the "out/cooled" fluid going back to the
transmission.. BUT I know for a fact that some radiators are set up different by the mfr.

You could also use a heat gun to make sure that your cooler in the radiator is indeed cooling,

As far as the converter is concerned, you would want some sort of a scanner to read
if the converter is being commanded to lock up and if it really is locking up - you should
be able to feel it locking up in 3rd and 4th gear

The tow/haul mode won't force the converter to lock up or unlock...
It just changes some the shift and locking strategies to deal with the extra load.
It will hold gears longer before upshifts and keep the converter locked up under
a larger throttle percentage (knowing your TPS is higher while towing)

 

[jabre]

@Foggy,

Fluid is correct. I have a FLIR camera that I can use to check for temp differential on the lines once it is hot and the cooling fan is running. I'll also give a go at monitoring the converter via OBD and watch for the lockup.

Thanks.

 

[swathdiver]

GM dealerships use the TransFlow machine to measure the flow of the transmission oil cooler lines and the cooler itself. If it is not within spec, they ought to be replaced or they will kill the transmission. Blowing air in them is the shade tree way if memory serves. Sorta works, but doesn't tell the whole story.

 

[jabre]

@swathdiver, it makes sense that the dealer has a dedicated system. If I knew the specifications of the flow rate I could likely use a stop watch with a graduated bucket to check the flow at the output of the radiator/cooler. I can't find the specification after spending some time online searching.

 

[Dustin Jackson]

It is stories like this that make me dread the day I need to replace my transmission. Worried that it will never be the same

 

[swathdiver]

@swathdiver, it makes sense that the dealer has a dedicated system. If I knew the specifications of the flow rate I could likely use a stop watch with a graduated bucket to check the flow at the output of the radiator/cooler. I can't find the specification after spending some time online searching.

Steel and Aluminum refers to the the material that the transmission cooler is made from. Any shop can own and use the TransFlow machine, there are undoubtedly newer machines out there that can do this as well.

 

[jabre]

@swathdiver, thanks for the detailed flow data. I may use it. But, decided to do a couple of other measurements first.

First, I found out why I was remembering the old tranny running at 185 while I keep seeing the interior engine temp gauge at 210. The thermostat is a 187deg set point.

I had the impression the radiator reserved some rows for tranny fluid cooling. I was wrong, I looked up radiator structures and found the tranny oil flows through a single cylinder immersed in the coolant in the radiator. So, running at 185 is right in line with the coolant flow through the radiator.

I received my new bluetooth OBD scanner. I only drove a few miles and already see the panel engine temp gauge is off. It quickly ramps up to 210 whereas the OBD coolant temp gets up to 185 and then slowly settles into 189 steady. The tranny temp really lags behind the coolant and only got up to about 165 in the time I was watching it.

I used my IR camera and couldn't see a difference in the input/outputs at the radiator. Likely it was still warming up. So, I ordered a couple of K type thermocouples that I'm going to use to contact the tranny fluid input/output pipes at the radiator and then log the temperature over a day of driving. Hopefully I can observe the differential temperature between the two pipes and save myself from measuring the flow directly.