lb7 transmission temps - Chevy and GMC Duramax Diesel Forum
01-04.5 LB7 Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

LinkBack Thread Tools Display Modes
post #1 of 5 (permalink) Old 09-12-2011, 12:33 PM Thread Starter
Junior Member
Join Date: Jan 2011
Posts: 65
lb7 transmission temps

hello, I have a 2004 lb7 2500HD crew cab 4x4 duramax with 170,00kms (110,000miles) that is stock except for a bully dog programmer running on economy mode. I bought the truck used so this is my first summer with it. My transmission temps seem very dependent on the outside temp. If the outside temp is 30 deg C (90 deg F) the transmission with heat up to about 95 deg C (203 deg F) in traffic in the city and about 90 deg C (195 deg F ) on the highway. However on a recent drive the temp dropped from 30 deg C to about 16 deg C (60 deg F) outside and the transmission followed down to about 65 deg C ( 150 deg F). In the winter the gauage almost does not move at all off 40 deg C. This is all with no pulling a trailer or any significant hills. If is annoying because as the trans temp rises the engine cooling fan kicks in. The actual engine temp always stays right around the middle or falls off to about 1/4 while the fan is on cooling the transmission temps. Is this normal? It seemed to have got a little better after I pressure washed the cooler and removed the aftermarket grill, but the fan still comes on quite a bit in normal driving. I am almost worried to tow a trailer on a warm day and have the transmission overheat. How can I fix this and lower the transmission temps?
martincc is offline  
Sponsored Links
post #2 of 5 (permalink) Old 09-12-2011, 12:34 PM
DuramaxForum Fanatic
DirtyMaxx03's Avatar
Join Date: Jun 2009
Location: Bulverde, TeXaS
Posts: 6,193
100* over outside temp is where the tranny where run

2003 Lb7 2wd
Efi Live by Rob Coddens
DirtyMaxx03 is offline  
post #3 of 5 (permalink) Old 09-12-2011, 12:35 PM
DuramaxForum Enthusiast
rebpdt's Avatar
Join Date: Nov 2010
Location: across the street
Posts: 3,774
Have you checked the fluid level and made sure it is properly filled?

CCSB LB7 4x4
rebpdt is offline  
Sponsored Links
post #4 of 5 (permalink) Old 09-12-2011, 12:37 PM
Im Superrrrr!
jmaz268's Avatar
Join Date: Apr 2007
Location: Central Illinois
Posts: 14,517
Send a message via Yahoo to jmaz268
Tranny temps are usually 100 degrees over ambient. the OE gauge for coolant temp is wrong more than it is right. If you have a scanner capable of reading it, go off that.

Goes by John
--2001 ECSB
SDP Big Single, Wehrli Dual Fuelers, 50% sticks, Front Coilover Conversion, Anorexic .....much much more

Sponsored by Creatures of the Night Performance and SDP
--2005 CCLB Dually
The tow pig
Tuned and Edge Insight CTS
jmaz268 is offline  
post #5 of 5 (permalink) Old 09-12-2011, 01:09 PM Thread Starter
Junior Member
Join Date: Jan 2011
Posts: 65
fluid is normal... I believe higher than the marks when shut off and right where it should be at idle. Truck shifts and drives fine. If the gauge was out, why does the cooling fan keep coming on to the point that it actually cools down the engine temps? on a wamn day (15-20degC) this is close to what I am seeing, however if the temps get about 25-30 (80-90deg F) outside this is when I see the guage get high.
martincc is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Chevy and GMC Duramax Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome