Ok, looking for some advice went to add wiper fluid couple days ago and noticed my coolant overflow had about an inch of strawberry quick at the top. I checked the tranny dipstick and sure enough found some in there also. Took the truck in and was told they will flush both systems and replace radiator for $800. My response was I had a friend have this also under his 100k Powertrain he got a rebuilt transmission new radiator all for $500. I just got the call back from my local GM shop and they will honor the $500 but just going to flush the transmission only and replace radiator. 2007 H3 78k miles -- my big concern is the transmission -- will it be ok with just a flush or should I be pushing for a rebuild? Had no issues prior or lights everything was working fine, but I have read that coolant (DEX) in your tranny is not good!! Any advice would be great!! Thanks!!

 

A friend had the same problem, same year.....had to have the trans replaced.

 

Engine coolant WILL destroy the transmissions friction elements. The friction material delaminates from the metal bands and clutches. I'd get the tranny replaced. Call GM direct.

 

sounds like you should try to get it replaced!!!!

 

How the hell does this happen? I just had my radiator replaced because it was cracked where it rubs where it mounts on the top. I had no idea that the coolant could get into the trans and vise versa. Mine is an 07 with 76k.

 

I also cannot see there the connection!
Usually the transmission cooler is separate attached to the radiator exactly to separate two systems and do not create such problems what we now get to hear about...could it be that we have here a design issue....maybe it would not be such a bad idea to modify to an external cooler.
Seeing now all the issues around the radiator at the H3...I'm sure that in case I get trouble, i will not just replace. There are many shops who tailor made radiators...and not with plastic components! What I see here is that GM does simply ignore problems...ok replace a few on warranty....we anyway do not build the H3 anymore...
!

 

The radiator in an automatic transmission has a section in it to cool the transmission fluid. The section is in a sealed off area from the engine coolant. If a leak develops the two fluids can mix. They run the transmission fluid through there to help get the transmission fluid temp up during cold weather for better shifting and also to cool the transmission fluid. You have transmission fluid on one side and engine coolant on the other side. It's just separated by metal tubing. You could reroute the hoses to a separate transmission cooler.