What's a "normal" trans temp range?
 

Knowing the issues with transmissions in LS4 cars, I drove my 26k mile GXP home for the first time last night. Cruising at 80 for awhile, playing with buttons, I came across the trans temp at 222. OUCH....

Slowed down to 65, and it was down to 195 within 15-20 minutes, and stayed there for the rest of the ride (80 degree night, no traffic). I sped up to 75, and it started climbing over 200 again, so I backed it down to 65.

Parked in the garage this morning, I checked the fluid. Clean, but smells burned (no shit, right??), and its down a little. I'm going to do a complete flush and put fresh fluid in on Monday. I don't remember my 04 GTP temp ever going over 190.

Do LS4 transmissions run hotter? Probably just old fluid, or maybe the trans cooler lines are blocked a little? Otherwise, all this car needs is the HUD replaced, and its a brand new 10 year old car! Any help is appreciated...

I would say most stock vehicles tranny temps are around 185-205 degrees.

If you were to add a aftermarket tranny cooler and bypass the one in the radiator your temps will drop massively.

I know my car is not a gxp but I put the B&m 70266 tranny cooler in and bypassed the radiator cooler and the highest temps I have seen are 180 on a 90 degree day beating on it on a road course.

I was just out beating on my car today and hit 155 degrees. That's also with a high stall converter.

On the highway in overdrive and the converter locked it will sit around 130-145 degrees depending on outside temp.

This past spring on a 50 degree day it sat at 112 degrees going down the highway at 70 mph

Because the miles are so low, and I've wanted a GXP for years, I'm probably gonna add a tranny cooler to it in the near future, regardless of how it acts after the fluid change.

I traded my beloved 14 Charger RT on my CTS-V, and now the GXP is to save miles on the V. I'm stuck with the GXP for a very long time...the V payment is not cheap :lol:

Those temps you are seeing is what the General deems "normal", although in reality too hot for most. LS4 transmissions for sure run hotter, the engine compartment heat soaks everything. Get yourself a transmission cooler, drain that fluid and change the filter. GM had a TSB on the transmission magnets(run 2), these pair from Home Depot are identical for about 16 bucks less.
https://cimg9.ibsrv.net/gimg/ls1tech...693a968c3c.jpg

What transmission do they put in the 08 g6 gxp A6 3.6L and the Ls4?

Do they both run the 6T70e ?

The HUD not working could be something as simple as a spring unhooked, or the switch is very inexpensive as well.

https://www.amazon.com/ACDelco-10438...iglink20380-20

LS4 cars get 4T65E HD, not sure on the rest.

Average temperature for me (engine/tranny fully warmed up) was between 190-205. It popped up to 224 once, so I threw on a transmission cooler last week (standalone). It has not gotten above 165 since (90-95 degree temps outside), with the same drive and sitting even longer in traffic.