Interior heat from engine unbearable

[OutInCreation]

When driving my 1991 HDJ81 at highway speeds (80-100 Kph) the heat coming off the shifter console is unbearable to the point I have to move my leg away. Anyone ever deal with this before? Any suggestions? I haven't removed the console yet to check things out yet but thought I'd throw this question out there.

 

[duncanrm]

Sounds more like transmission heat.. is it an auto?

 

[OutInCreation]

Sounds more like transmission heat.. is it an auto?

yes

 

[duncanrm]

yes

I'd find a local auto trans specialist.. maybe an external cooler is required, especially if towing.

 

[IanB]

North American 80 series came from factory with trans coolers, HDJ81's did not for some reason. Especially with a turbo upgrade, an external trans cooler is probably a good idea.

That being said, I don't think it's going to help at all with the center hump heat transfer issue you're having. I'd start by pulling the console and ensuring the rubber boots around the shifters are still intact, that can allow heat to flow up and into the cabin easily. Check the steering shaft grommet as well. If they check out, then you might want to consider using fatmat or similar foil backed mass adder on the center hump surfaces to reflect heat back and keep it out of the interior.

 

[Gimme a 60]

Does the A/T idiot light not come on when it’s too hot?

Sound deadening may help keep heat out.

 

[Squash]

You may want a tranny temp gauge, and drive accordingly.
My 91 with A442 is in Whistler BC.
Drives nice and cool in 4th gear all day, downshift and watch the heat rise quickly.
According to my son even low range does the same sort of heat thing, fine in 4th, but heats up in other gears.
He added a cooler, but that hasn't changed the results.
Transmission was rebuilt, so back to the drawing board.

 

[IanB]

You may want a tranny temp gauge, and drive accordingly.
My 91 with A442 is in Whistler BC.
Drives nice and cool in 4th gear all day, downshift and watch the heat rise quickly.
According to my son even low range does the same sort of heat thing, fine in 4th, but heats up in other gears.
He added a cooler, but that hasn't changed the results.
Transmission was rebuilt, so back to the drawing board.

A '91 will be a fully mechanical A442, TC lockup only in 4th. Basically, driving with a trans temp gauge, you see trans temps rise anytime the trans is working, and not in lockup. Climbing grades in lower gears, makes a lot of heat!

 

[duece71]

I sometimes experience the heat on the console when driving but it’s not unbearable. While attending GSMTR last month, the initial climb, which was on pavement to get to the start of the trails at Windrock…..yes, saw trans oil temps climb to 220-230F. I should have been in Low but I don’t have the 7 pin mod to shut off the CDL in Low. Once I shifted into Low, trans oil temps decreased to 180F and stay there while moving over terrain. I installed the WA universal cooler up front last year and I am sure it has made a difference in temperature. The HDJ81 radiator has transmission fluid lines in the bottom of it but I think this feature is more of a heater than a cooler.

 

[mudgudgeon]

North American 80 series came from factory with trans coolers, HDJ81's did not for some reason. Especially with a turbo upgrade, an external trans cooler is probably a good idea.

That being said, I don't think it's going to help at all with the center hump heat transfer issue you're having. I'd start by pulling the console and ensuring the rubber boots around the shifters are still intact, that can allow heat to flow up and into the cabin easily. Check the steering shaft grommet as well. If they check out, then you might want to consider using fatmat or similar foil backed mass adder on the center hump surfaces to reflect heat back and keep it out of the interior.

This.

My hdj81 was manual trans, but on a long trip everything gets heat soaked. A lot of heat comes up through the floor pan, abs through the trans tunnel.
There's very little insulation on the floor.

I insulated under the carpet with a couple of layers of foil backed thermal insulation to reduce heat and sound transfer. Insulating the floor pan and trans tunnel hump helped a lot.

The thing that really put the icing on the cake was insulating around the shifters under the centre console. With the floor insulated, it became really obvious that a lot of heat came in around the shifters, even with rubber boots intact.

There's some good threads discussing insulating the floor on 80s-tech