What temperature should the TH400 run at?

[Chevybrit]

And where and what type of temp sender have you fitted (if you have)

Thanks

 

[rustystud]

The temperature should stay between 150F and 180F degrees. If you go above 220F your looking at cooking your transmission. I have my temperature gauge sender mounted on the oil pan.

 

[doghead]

Please search before posting new threads, many time you will find what you're after already is out there.

Feel free to post on existing threads if they do not completely answer your questions.

https://www.steelsoldiers.com/showthread.php?63660-TH400-temp

https://www.steelsoldiers.com/showthread.php?55315-TH400-Temperature

 

[rustystud]

I'll answer the sender part for you. I went with the sender in the oil pan as that is the area the manufacturer suggests. Some people like to put one on the "converter out" port. The problem is that is always going to be hot. There is no factory specs for that area either. Most aftermarket oil pans will come with a 1/4"
NPT port already in the pan for the sender. Here's a picture of mine.

 

[cucvrus]

That port will be fine for a highway cruiser. But in slight brush use it's a goner. I would knock that off in 1 week end while out doing wood cutting and fence stretching. My newer Chevys have trans temp sensor's and they are not in the pan. maybe inside. I think 34 years after being without one and dishing everything back at the CUCV with no issues I will settle to go without one some more. I have seen a few plumbed into the lines via a few brass fittings. seems to be accurate enough. Matt5 I feel your pain. been there. I always try and help. No harm done IMHO.

 

[DREDnot]

The temperature should stay between 150F and 180F degrees. If you go above 220F your looking at cooking your transmission.

Eh...that's a pretty conservative range of temps. You are definitely correct in that you wont' damage anything if you can maintain those.

trans temps same as engine temp...~195*...is pretty average. The "perfesser" of transmissions at GM Tech Institute (1987) told us that the seals and O-rings were the weak link and would harden (and leak line pressure) at temps over 265*. The leaking line pressures would let clutches slip...causing more heat that would then start breaking down the oil. Then the friction material would bake in a cascading effect.

His recommendation was 245* max, and severe service oil change schedule. That's been my personal limits that have been tested and found to be satisfactory for this last thirty years of fiddling with stuff.

I concur with the oil pan sender mounting. The temps in the converter can get real hot...350 ish? and cooling line placement doesn't give you the added cooling at the pan. They are most concerned with what temp the oil is at when it enters the trans and begins to pick up heat. Here is where a deep HMMWV pan, or finned aluminum aftermarket pans really help.

 

[Chevybrit]

What happened to Matt5's comment? I wanted to add that many of the threads get cross posted all over them and very quickly off topic.. It can take a while to sift through many pages for the final answers

 

[rustystud]

That port will be fine for a highway cruiser. But in slight brush use it's a goner. I would knock that off in 1 week end while out doing wood cutting and fence stretching. My newer Chevys have trans temp sensor's and they are not in the pan. maybe inside. I think 34 years after being without one and dishing everything back at the CUCV with no issues I will settle to go without one some more. I have seen a few plumbed into the lines via a few brass fittings. seems to be accurate enough. Matt5 I feel your pain. been there. I always try and help. No harm done IMHO.

The sender is high on the side of the oil pan. It would take some serious brush to reach that area.

 

[rustystud]

Eh...that's a pretty conservative range of temps. You are definitely correct in that you wont' damage anything if you can maintain those.

trans temps same as engine temp...~195*...is pretty average. The "perfesser" of transmissions at GM Tech Institute (1987) told us that the seals and O-rings were the weak link and would harden (and leak line pressure) at temps over 265*. The leaking line pressures would let clutches slip...causing more heat that would then start breaking down the oil. Then the friction material would bake in a cascading effect.

His recommendation was 245* max, and severe service oil change schedule. That's been my personal limits that have been tested and found to be satisfactory for this last thirty years of fiddling with stuff.

I concur with the oil pan sender mounting. The temps in the converter can get real hot...350 ish? and cooling line placement doesn't give you the added cooling at the pan. They are most concerned with what temp the oil is at when it enters the trans and begins to pick up heat. Here is where a deep HMMWV pan, or finned aluminum aftermarket pans really help.

You correct in that my "opinion" of the best operating temperatures is on the conservative side, but after working on transmissions for some 40 years I found these temps to be the best to stay in for the life of the transmission. Also oil starts to break down at around 250 degrees. So I never go above 200 degrees on my personal transmissions. Actually I have never gone over 185 on my TH400 in my CUCV even towing the trailer over the Snoqualmie Pass (around 3,000 ft.) in summer with temps in the 90's . I have two transmission coolers besides the radiator cooler. If your always "pushing" the limits of your transmission, sooner or later you will find them.

 

[cucvrus]

The sender is high on the side of the oil pan. It would take some serious brush to reach that area.

You never went in the multi flowered roses that we have here in south central Pennsylvania. Wicked on a vehicle and tires. I like the skid plate option but it holds 50 lbs of mud and helps to keep the transmission hotter. How high can it get when the pan is about 3" deep?

 

[Floridianson]

Don't know where this came from but here it is.

 

[rustystud]

You never went in the multi flowered roses that we have here in south central Pennsylvania. Wicked on a vehicle and tires. I like the skid plate option but it holds 50 lbs of mud and helps to keep the transmission hotter. How high can it get when the pan is about 3" deep?

The depth of the pan doesn't matter as the sender is at the top, not the bottom. I agree though it should have some protection if your going out into the boonies. A simple little brush guard would be simple to make. Actually if your going out into the boonies and expect such nasty things to get into the transmission area you should install a skid plate. Remember there is also linkages and modulator hoses and cooler lines that could be damaged too. Just saying.

 

[ken]

Eh...that's a pretty conservative range of temps. You are definitely correct in that you wont' damage anything if you can maintain those.

trans temps same as engine temp...~195*...is pretty average. The "perfesser" of transmissions at GM Tech Institute (1987) told us that the seals and O-rings were the weak link and would harden (and leak line pressure) at temps over 265*. The leaking line pressures would let clutches slip...causing more heat that would then start breaking down the oil. Then the friction material would bake in a cascading effect.

His recommendation was 245* max, and severe service oil change schedule. That's been my personal limits that have been tested and found to be satisfactory for this last thirty years of fiddling with stuff.

I concur with the oil pan sender mounting. The temps in the converter can get real hot...350 ish? and cooling line placement doesn't give you the added cooling at the pan. They are most concerned with what temp the oil is at when it enters the trans and begins to pick up heat. Here is where a deep HMMWV pan, or finned aluminum aftermarket pans really help.

You are correct. In stock configuration the trans cooler is routed into the drivers side "HOT" side of the rad. If you are running the stock 195 deg thermostat the best you could hope for is 195. If you are towing/hauling and the engine is getting hotter, then the tranny will also. This is why when installing a extra cooler you route it after the rad, otherwise the engine just reheats the fluid before is returns. The quickest and easiest way to lower tranny temps in a CUCV is to install a 180 thermostat. This will expose the fluid to 15 deg lower temps.

 

[MarcusOReallyus]

You are correct. In stock configuration the trans cooler is routed into the drivers side "HOT" side of the rad. If you are running the stock 195 deg thermostat the best you could hope for is 195. If you are towing/hauling and the engine is getting hotter, then the tranny will also. This is why when installing a extra cooler you route it after the rad, otherwise the engine just reheats the fluid before is returns.

Heh. I've been saying the same thing, and getting yelled at for it, on many 4x4 forums. But it's basic thermodynamics. If you want the coolest trans fluid temps, you cool after the radiator.

The quickest and easiest way to lower tranny temps in a CUCV is to install a 180 thermostat. This will expose the fluid to 15 deg lower temps.

Not really a good idea to run a lower t-stat. The engine is designed for a particular temperature. Putting in a lower T-stat doesn't make things better. It's a band-aid.

 

[ken]

Original equipment on the early 6.2's was a Robert Shaw 370-180 thermostat. Every early Civi 6.2 I had, had one. My 82 GMC K2500 came with one and a 7 blade 20 inch fan. It's the EPA forcing engines to run hotter. I can totaly understand someone in a cooler climate running a 195. In Texas with a 195 and a 5 blade fan it's hard to haul or tow anything with out overheating and blowing head gaskets. I could only guess how hot the torque converter might be.

 

[rustystud]

Heh. I've been saying the same thing, and getting yelled at for it, on many 4x4 forums. But it's basic thermodynamics. If you want the coolest trans fluid temps, you cool after the radiator.

You correct. All after-market coolers should be installed after the radiator. That's how I was able to tow my RV trailer over Snoqualmie Pass in 90 degree weather and have my transmission only go up to 185 degrees. On big rigs they never use the engine radiator to help cool the transmissions. Just large stand-alone coolers with built-in thermostats to allow the transmissions to reach operating temperature sooner.

 

[Barrman]

What about the other way? What is the minimum fluid temperature an automatic transmission should be used at beyond just idling along? I ask because besides just being curious. I have a 4L80E in my Cowdog truck and the TCM tells me the fluid temperature. That is an internal sensor so it would be different than what the add on TH400 temperatures are.


I personally don't give it more than just idle power until the engine coolant is above 140°, engine oil above 120° and transmission above 90°. That is just me trying to make everything last my lifetime and beyond. Is there a minimum for ATF?


Just to jump on the band wagon too. There is a lot of shouting people all over the internet claiming different things about where to place and how to plumb a transmission cooler. However, all of the transmission rebuilders and aftermarket cooling products makers have the same information. Radiator and then air to air cooler then back to transmission. Listen to people who live with them daily.

 

[MarcusOReallyus]

all of the transmission rebuilders and aftermarket cooling products makers have the same information. Radiator and then air to air cooler then back to transmission. Listen to people who live with them daily.

They are selling transmission COOLERS. They are interested in COOLING your transmission, because that is what their customers want. They don't care if your transmission dies early from struggling with too-cold fluid. Yes, it can be too cool, as your question indicates.

If you live in a very cold climate (Alaska, Montana, etc.), plumbing it in AFTER the radiator is probably a mistake. For most of us, that's the right place.

But for maximum cooling, put one before AND after the radiator.

 

[rustystud]

What about the other way? What is the minimum fluid temperature an automatic transmission should be used at beyond just idling along? I ask because besides just being curious. I have a 4L80E in my Cowdog truck and the TCM tells me the fluid temperature. That is an internal sensor so it would be different than what the add on TH400 temperatures are.


I personally don't give it more than just idle power until the engine coolant is above 140°, engine oil above 120° and transmission above 90°. That is just me trying to make everything last my lifetime and beyond. Is there a minimum for ATF?


Just to jump on the band wagon too. There is a lot of shouting people all over the internet claiming different things about where to place and how to plumb a transmission cooler. However, all of the transmission rebuilders and aftermarket cooling products makers have the same information. Radiator and then air to air cooler then back to transmission. Listen to people who live with them daily.

Your correct about there being a "minimum" temperature. Most manufactures say it's between 130-150 degrees. If you start getting "knarly" on your transmission before it reaches operating temperature you can damage the seals and clutches.
That's why most all big rigs (that use automatic transmissions) and busses have a oil thermostat on the cooler. It will not allow the oil to enter until it reaches operating temperature.

 

[Barrman]

Ok. 130° is a good number to know. Thanks.