4RnrRick

What the purpose of the black cylinder (looks liek a small air tank) under the exhaust manifold? Is it a some kinda of secondary tranny cooler? Seems like a terrible spot to if its a cooler.

Or is it a coolant heater - but then why is Tranny lines going to it?

If this has been asked, Sorry - please just point me to some info about it.

Rick

Tuckerdee

It is THE transmission cooler. It's a oil/water heat exchanger. It's actually quite efficient...as some have found out that wanted to remove it and run some sort of other cooler...as the transmission has a REALLY hard time running cool enough without it. There's another, this one secondary, tranmission cooler in the grill. It's on the driver's side mounted kind of high.

4RnrRick

So does that mean the "tow package" models have another one (third unit) mounted up under the bed???

If so , thats just NUTS!

Tuckerdee

Uh, not sure if that was a "tow package" item, but it was an option. There was a third, fairly hefty, cooler under the bed with, I think, a fan included. But I've never actually seen one. Mine will have that option soon, though.

Tuckerdee

The water/oil heat exchanger also serves to heat up the transmission fluid in cold conditions. Part of the requirement for shifting into O/D is a certain transmission fluid temp. And you'll see that sensor in the line fron the tranny to the heat exchanger right below the bell housing, basically. So, again, bypassing it isn't really advised.

wannadiesel

Not quite. There is a minimum coolant temp required for the trans to allow OD engagement, the PCM uses the coolant temp sensor for that. The sensor in the line is an over-temp sensor that kicks you out of OD at 285 degrees (too late!).

Tuckerdee

Oh, Wanna, of course you're right...again.

wannadiesel

Yeah, except I quoted the wrong post in my reply.

tomd

Yes
This is what I have in my truck.
And It does have an electric fan with it.
I thought this was aftermarket?

wannadiesel

Nope. Dealer installed option.

Jim Lane

This is what the auxiliary transmission oil cooler looks like on my 1991 D-350.

Front,




Middle,




Rear,



Jim

Begle1

Hmmm... Did gassers have that option, perchance?

4RnrRick

Where did it tie into the tranny hydraulic lines at??

Chass

That surprises me because I've never seen a 92 or 93 auto without this cooler and they all look exactly the same.

Sad thing is that these trucks have a really rough time keeping their tranny temps down even with all 3 coolers working properly. I can easily peg my tranny temp guage at 250 towing up a 1 mile long hill in OD. Of course I don't run it in OD up the hills for that reason but it gets hot quick even out of OD.

Chass
ct

dpuckett

Your heat could be due to the gasser high stall convertor that came stock in these trucks.

DP