A442F transmission overheating (HDJ81) (1 Viewer)

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My truck is a 92 HDJ81 with the full hydro A442F, running into some issues towing my travel trailer with it. I currently have a dedicated 34 row Derale stacked plate cooler attached to the transmission and disconnected from the radiator, I only run into heat issues when I am pulling the trailer up steep inclines here in the PNW (usually makes it through 3 or so 5% or greater grades (each quite a few miles in length, 4-5 miles or so) I have had the overheat light come on a couple of times (truck is not in OD during this), it cools off quickly enough and I am able to carry on so long as I keep the speeds up or allow it to kick into overdrive. Trailer weighs 3k lbs (I don't fill it with water etc...) empty and 3200lbs with minimal stuff inside the trailer.

I have flushed all the ATF out (multiple times to ensure it's fresh when this happens), last year when it was attached to the radiator and a smaller (9 row stacked plate Derale aux cooler) it caused my radiator to boil over (but the ATF light never came on) when towing. Removing it from the radiator (I installed a 4 row manual trans radiator) fixed those issues, and so long as I tow on less steep grades or at highway speeds it doesn't overheat the transmission. Without towing I can do slow rock crawling to whatever just fine with no heat issues all day in 100 degree weather. I don't have a temp gauge yet, but I do have one on order. Fan clutch hub has been replaced with a new OEM one, and has heavier oil in it (it works great at keeping things cool). Installing a hefty electric fan to the trans cooler to help a bit as well.

My question is this, is the torque converter to blame for it getting too hot (it locks up fine in 4th) along with it being removed from the radiator? Should I get an auto trans radiator and hook it back up properly? I've seen other HDJ81s towing heavier trailers than mine in the PNW (autos) to the same areas and they don't have the issues I have, so I'm just trying to figure out if I need to drop the trans and replace the torque converter, or really double down on cooling for it.
 

GTSSportCoupe

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Anytime the torque converter is not in lock-up it'll be creating a huge amount of heat. Your best option is to buy an aftermarket valve body that allows the torque converter to lockup in 3rd and 4th. Tow in 3rd and keep it in lockup as much as possible. I think the Australian company 'wholesale automatics' makes a good valvebody for the a442f.
 
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Fair enough, looks like I'll be ordering one of those.

Anytime the torque converter is not in lock-up it'll be creating a huge amount of heat. Your best option is to buy an aftermarket valve body that allows the torque converter to lockup in 3rd and 4th. Tow in 3rd and keep it in lockup as much as possible. I think the Australian company 'wholesale automatics' makes a good valvebody for the a442f.
 

sailor

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your best option is to get a full sized pick up! lol. the valve body will help, it is critical. the problem will persist, however until you are able to achieve lock up win third, which will happen at 45 mph or so. until this speed is achieved and the TC locks, BBQ city!...
 

GTSSportCoupe

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This is why I have two sets of tires for my auto box landcruiser. Small 32" tires for towing, and 35" tires for fun and offroad. The 32" tires allow me to achieve lock-up at a lower speed while towing and keep the heat down. A343F in mine locks in 3rd and 4th from factory.... I try to hold that 3rd gear as long as possible when climbing hills and towing on the highway. When it drops to 2nd temps rise.
 
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I really should get towing specific tires, however it’d look pretty funny with the lift I have but it’d at least be functional. I’ve reached out to Cruiser Brothers for a quote on a valve body (sucks I can’t just outright order it from their site but such is life).

I installed a second 34 row cooler with a fan as well, maybe it’ll help hold me over a bit until the valve body gets in.

This is why I have two sets of tires for my auto box landcruiser. Small 32" tires for towing, and 35" tires for fun and offroad. The 32" tires allow me to achieve lock-up at a lower speed while towing and keep the heat down. A343F in mine locks in 3rd and 4th from factory.... I try to hold that 3rd gear as long as possible when climbing hills and towing on the highway. When it drops to 2nd temps rise.
 
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A442 is known for being prone to overheating. Disconnecting the ATF cooler in the radiator was a mistake. Optimal ATF cooling is achieved by retaining the OEM cooler in the radiator and then going through an additional/aux cooler. I’d suggest changing your plumbing and seeing what effect it has.

Valve body will help but a far cheaper option is to instal a manual lock-up switch for the TC. IIRC this will enable you to lock the TC in 3rd without the need for a valve body (though worth confirming..). You can either buy a switch from someone like Wholesale Autos, or there is a thread somewhere on how to do it..... Both is obviously better - it enables you to lock the TC in any gear.
 
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Mine is the full hydro unit, the 93s and above have that ability (electronic 442s). Unfortunately as far as I know I need the valve body to achieve 3rd gear lockup


A442 is known for being prone to overheating. Disconnecting the ATF cooler in the radiator was a mistake. Optimal ATF cooling is achieved by retaining the OEM cooler in the radiator and then going through an additional/aux cooler. I’d suggest changing your plumbing and seeing what effect it has.

Valve body will help but a far cheaper option is to instal a manual lock-up switch for the TC. IIRC this will enable you to lock the TC in 3rd without the need for a valve body (though worth confirming..). You can either buy a switch from someone like Wholesale Autos, or there is a thread somewhere on how to do it..... Both is obviously better - it enables you to lock the TC in any gear.
 
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I have the same transmission with the extreme nomad valve body WAT and it definitely helps. I still over heat and very windy roads where i cant get up speeds and this is not towing.
If I was you I would
1. Definitively loop that radiator back in as is much more efficient at the low speeds you are towing since the the fan is always working to extract heat.
2. Add a real temp gauge in place of the OEM one.
3. Can you show me pic where you added the transmission cooler with the fan?
 
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I feel your pain. Installing a Derale 13870 (40 row cooler / 67,000 BTUs) this week to avoid the problem moving forward. As far as I understand it, the cooler in the radiator acts more as a heater than a cooler so if your engine temps are high that radiator cooler isn't helping. That's why its important to place your aux cooler after the radiator.

Are you still overheating with your 34 row Derale or have you not tested that yet? Its 59,000 BTUs, right? That's some pretty serious cooling...

I spoke with Georg (Valley Hybrids) about this fairly recently. While the Valve Body will help, you're looking at a 4-6 week lead time and you're expected to provide your own valve body (they are very hard to come by) so your truck will be down for a while. The billet TC apparently helps too, but the VB would be my first choice.

I've read through lots of threads on the valve body where people are still dealing with dangerous temps. You can always add multiple coolers, which is something im willing to do if this single Derale doesn't do the trick...

BTW, I spoke with a couple remote cooler manufacturers (i.e. fan + plate) seeking advice on placement since i've seen a few people on here talk about the need to keep the cooler as close to the transmission as possible. The consensus from the manufacturers is that mounting in the rear tire carrier area would be fine and shouldn't cause any issues. I guess we'll see, but with so much space back there I could fit some serious cooling power...
 
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The rear of the truck would be awesome actually, I’d much rather plumb the lines back there to cool it vs hanging everything off the front like I have now.

Mine overheated with the 34 row (no fan at the time) it took a much longer time to overheat while towing and cooled off much quicker, but after the 4th super long hill in a row the light went on and I had to pull over for a minute for the light to go off. It went a lot further than when I had the smaller 19 row one in there. Right now I have the two mounted in the front which isn’t ideal since they hang a bit low, and block a lot of the intercooler now. Good air gap though, and the two fans pump a lot of air.

I’d normally just have the one 34 row in and call it good since with it installed it never once overheated while not towing, no matter what I did to the truck even with a single 16 row 32k BTU cooler. Only overheats towing up the hills, never on the highways since it’s in OD.

But with the girlfriend getting on me to tow the trailer out for a workcation I have to make sure it stays cool for the trip. Once that’s done it’ll be back to the one cooler with the fan because I’m more worried about having the truck ready for snow wheeling this year. Next year I’ll have a 3/4 ton Diesel to tow the trailer around and let this just be my vanlife/snow wheeling truck like it deserves.
 

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