Thermostat thought...

[Chevy1925]

So in my truck, if i am in a looooong down grade with the trailer fully loaded on the back of the truck and i use the truck to slow me down, i will have issue with the trans overheating. this ONLY when in a down grade situation and i am running 3500-3700rpm to slow my rig down hill. I can watch coolant temps drop to the point they close, EGT's in the 200-250* range, Oil temps in the 180* range and basically everything cooled off ACCEPT the trans. initially it will cool from 210 or where ever i am about 10-15*, they temp starts to raise about 2/3 the way down the long grades im on. it did this wtih my old radiator and stock air to oil cooler and it has now done it with my Setrab cooler from Mike and the new radiator.

What im figuring is going on is the thermostats are closed so fluid is no longer circulating and now the water around the heat exchanger is heating up with no place to go so the trans starts heating up. the fan isnt on either so no air coming across the trans cooler at 50-55mph. Now when i run my solid hub, it may help but im wondering if anyone has tried running a 160* race thermostat in one spot and a 185 or 180* thermostat in the other. i figure ill run the 160 in the water pump bypass area so the pump will continue to circulate till temps drop below 160. i figure this way, the other higher temp thermostat will let me get up to a semi decent temp still so i have heat in our "cold az winters".

thoughts? wonder if id have too high of coolant pressures from the water pump if the 185 or 180 isnt open yet? though i figure that would have shown up as an issue already with the WOT cold runs i did years ago trying to set the rings in

 

[Awenta]

Try running without the thermostats. Or just keep them out in the hot months

Are you going to drive it in the winter anyway?


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[JRein]

You need the thermostats in to create a pressure difference otherwise you'll cavitate the water pump

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[hondarider552]

No tstat it will overheat

 

[ZeroGravity58]

You can take the t-stats out and run a restrictor. I used to run them in my race rigs with electric water pumps. It does take some trail and error to find the right one(s) tho...

 

[moparkxracer]

Did you cut the check balls out of them?

 

[gmduramax]

Drive faster downhill :thumb:

 

[2004LB7]

Is the transmission converter locked or unlocked while it is getting hot?

I have mine unlocked in "normal" while coasting and locked in TH while coasting. While I likely don't tow as much as you i have not had any issues

 

[JoshH]

Is the transmission converter locked or unlocked while it is getting hot?

I have mine unlocked in "normal" while coasting and locked in TH while coasting. While I likely don't tow as much as you i have not had any issues

If he is using the engine to slow the truck, chances are pretty good that the converter is locked while this is going on.

 

[2004LB7]

Just trying to figure out where all of the extra heat is coming from

 

[JoshH]

The elevated pressure in his built trans creates more heat that is likely made worse by extended high rpm operation.

 

[A. Stock Lbz]

I would start by drilling 3 1/8th in holes in one thermostat so when it is closed it will still circulate a little water.

 

[Chevy1925]

T-stats will not be coming out nor will I put restrictors in. For one, you would have to block the water pump bypass tube to do restrictors and second, the orifice size is very particular. I don't want to be running up and down hills all summer just trying to get that figured out.

She gets driven more in the winter here than summer between dune trips and nice cruises, it's generally when I drive it the most but I don't hit the hills I do in the summer. There are two short 6% grades that I can pull in 5th gear and temps don't even move till I'm cresting the top lol. Summer is the killer on my truck

There are no check balls in these t-stats, just a bleed hole in each

Converter is locked the whole time. Like josh said, my built trans, heavy weight and high rpm is getting it hot. Iirc the trans pressures are in 320psi range.

I don't want to drill holes. I've done that in other vehicles and it just prolongs warm up time. Plus I don't think that's going to be enough water. I already have the turbo return to the top of the thermostat housing so that is a decent amount of water circulating around the thermostat

Not tying to be negative to these ideas so sorry if that's how it's coming across. It's stuff I've tried before on other rigs and I know the down falls to them already. Only thing I have not seen is someone trying a thermostat setup like I was thinking. This is also assuming the engine doesn't cool its self down enough to the point the 160* stat closes too lol

 

[JoshH]

Not to be a Debbie downer, but I suspect a cooler thermostat will only delay the temp rise rather than fix it. However, it may be just enough to keep your temps from getting too out of hand before you get to the bottom of the hill. Have you considered adding an exhaust brake so you don't have to spin the engine RPM so high?

 

[rcr1978]

I wonder if the G-Solenoid for the trans would help, I can't remember for sure what the parameters were for it all I see is RPM and a few temp setting in the newer OS's? I thought I saw a TPS setting for it at one point that said it only was on under 3%TPS but don't see it now.

I know your trans doesn't have it but if Mike or someone that knows a little more about it could confirm the operating parameters for it you could add it just the cost of the valve body may not be worth it.

Edit: Looks like newer pump might be needed but can't tell for sure I thought it dumped right to the pan and I seen in a schematic it mentioned low speed so it will likely be a lost cause.

 

[Chevy1925]

Not to be a Debbie downer, but I suspect a cooler thermostat will only delay the temp rise rather than fix it. However, it may be just enough to keep your temps from getting too out of hand before you get to the bottom of the hill. Have you considered adding an exhaust brake so you don't have to spin the engine RPM so high?

thats my other thought was adding one. have to see how hard it would be to add one in with the twins in the way. 3500rpm will hold everything back extremely well. she can sit at 55mph the whole way lol. its interesting to me that the allison will grade brake to that high of an rpm cause IIRC, stock they dont go above 3250 unlike an LBZ and up. maybe due to my higher RPM shift points for WOT?

either way, i think your right on it not really fixing it. hmmmm

RCR, i have a g solenoid in the trans right now but it is not in the valve body (no spot for it). Mike threw it in for me last go around to try out some 04.5-05 TCM tunes and not throw the G solenoid code. Then i realized the wire isnt there from the TCM back lol. I believe the truck also must be at idle for the solenoid to engage. i dont know if i really want pressure to knock down with the way mike has the trans set. he would have to tell me "dont do that stupid" or "you can try it without issue" assuming it would actually drop pressure when no throttle is applied as i grade brake.

 

[2004LB7]

What about plumbing in a small electric water pump to circulate the water in the radiator to keep it from warming up at the trans cooler?

 

[clrussell]

I'm just over here like man a 68r with turbo brake tuning would keep you from having to turn the rpm you do down hill.

 

[Chevy1925]

I'm just over here like man a 68r with turbo brake tuning would keep you from having to turn the rpm you do down hill.

now you are sounding like i do when i give you advice :roflmao:

 

[Dozerboy]

Do you really think the warmer trans temps going down hill are going to cause you and issue? Im just thinking you already know most things you could try are going create more issues for you. Maybe you should just deal with the temps.

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