Does your transmission tunnel get hot as hell?

[Htchevyii]

So, as many probably know, we take many very long trips in our ancient MJ. The biggest issue that we have is excessive heat inside of the cab. We've been fighting this for years and I've tried multiple times to correct it.. what I've done:

-Massive hood louvers. These did drastically reduce under hood temps. I can't even cook a burrito in the intake now 

-The interior floor and tunnel have been painted with ceramic paint, followed by reflective Dynamat, covered with adhesive foam insulation and a DEI transmission tunnel blanket. The inner shift boot was replaced. 

- the factory jute insulation and carpet covers all of this. 

While it's fine on short trips, heat builds to an almost unbearable level after several hours. The tunnel near the transfer case shifter still gets hot enough to burn you. 

 

I'm running out of ideas at this point. Trans is a brand new AX15 with Redline fluid. T/Case is rebuilt with ATF+4. 

 

I guess that I'll take a drive and check some temps  and see if I get any ideas, but it seems ridiculous that it's still getting this hot! I think that a heat shield between the trans and floor would be ideal, but I don't want to pull the transmission to do so. There isn't a cat in it.

[89 MJ]

Is it just as bad in high and low range?

 

My truck has rubberized undercoating, then the floor, then Chassis Saver paint, then Dynamat, and then carpet and it doesn’t seem to get very hot. The farthest I have run it recently is about 90 miles each way though. 
 

I wonder if it would be worth trying 10W30 in the trans, per Chrysler’s TSB or whatever it’s called. 

[Pete M]

yup.  heat can be a real issue.  the heat of the engine bay gets directed right down the tunnel along the transmission as you drive.  .

[Htchevyii]

I'm really wishing that I put some sort of heat shield on the firewall and bottom of the transmission tunnel when the engine and transmission were out. I think that would be more effective than trying to stop it ion the inside once the metal is already hot. Those 80 MPH Nevada speed limits don't help.

[Htchevyii]

1 hour ago, 89 MJ said:

Is it just as bad in high and low range?

 

My truck has rubberized undercoating, then the floor, then Chassis Saver paint, then Dynamat, and then carpet and it doesn’t seem to get very hot. The farthest I have run it recently is about 90 miles each way though. 
 

I wonder if it would be worth trying 10W30 in the trans, per Chrysler’s TSB or whatever it’s called. 

The Redline MTL was recommended by Advance Adapters and is supposed to meet the requirements of 10w30? It seems to be more of an issue at HWY speeds. You'd think that there would be enough air blowing underneath to cool things.

 

Satisfies the gear oil viscosity requirements of 75W, 80W and motor oil viscosities of SAE 30, 10W30 and 5W30

Recommended for GL-1, GL-3 and GL-4 applications as well as where most special synchromesh fluids are specified.

[Eagle_SX4]

I had excessive heat on the transmission tunnel when I bought my truck. My issue was there was no shifter boot and there was a hole in the top of the transmission tunnel that was just open. I plugged both of those and the heat in the cab stopped almost completely.

 

I wonder if your transfer case shifter is not sealed to the floor. Letting in just enough air that over time it heats everything up. I would pull it out and put some kind of sealant on it.

[Htchevyii]

I'm getting ready to pull the console out and check things out. I also would not be surprised if my "new" inner shift boot was made of crummy rubber and is disengraded. I will definitely be taking a close look at the transfer case shifter area.

[Tex06]

X2 on redline. I filled my AX-15 with 10w-30 synthetic, GL-3, GL-4, and MTL and recorded temps on my tranny case on each over a week or so using an IR thermometer. From memory the MTL was about 15deg F cooler in my daily commute than any other fluid.... the full synthetic motor oil was definitely the hottest. 

 

I was running around in 90-95F New Orleans weather. 

 

 I would definitely check your inner boot, those don't last long with the high temps. Also, the addition of louvers in the hood may cause the air under the truck to remain stagnant so although the under hood area is cooler, the transmission tunnel is actually hotter. 

 

 

[pizzaman09]

I have also observed a lot of heat when my upper shifter boot was removed.  The lower boot is completely disentigrated but with the upper one in place it isn't noticable.

 

I could picture adding an air scoop under the truck to pull some fresh cool air up there to flush out the hot air.