hey guys how hot should my tranny be getting?

96 automatic

the car has been giving me issues lately when the trans gets hot. starts falling out of gear or slipping. feels like it might as well be in neutral

trans got to 230 degrees today. engine around 195-200
wasn't on it too hard

just changed the fluid and filter. fluid looked good and not too much on the magnet in the pan

are there heavier duty clutches or a trans cooler that can help this available?

 

I do NOT know exactly what the "normal" operating temp for that trans is supposed to be, but I CAN tell you that any hydraulic pump/system does get pretty hot pretty quick.

This happens because the pump has to generate pressure on fluid to push it thru tiny orifices that are control devices. The byproduct of generating pressure via forced passage is HEAT. Resistence = heat. Resistance =pressure= power that's generated to serve as the means of making something happen...in this case, the "transmission" of power from a rotating shaft thru fluid to a Different rotating shaft...
Seems almost idiotic when you say it like that...!
But, that's an automatic transmission. Basically its a hydraulic pump submerged in its own sump/reservoir with its servos in the same tank (pan/case).

Since this system is pretty much self contained, there is no place for heat to escape. No way to dissipate the heat as its being produced like a normal hyd system would be able to do since its various components are in different places.

But, the automatic trans does have one place to dump off some of this heat by sending a small amount thru the radiator where its a SAFE assumption that the radiator TEMPS are going to be cooler than the trans temps, most of the time...otherwise there would be no point in sending trans fluid THERE to "cool" off...

Next time you are under the hood and the engine is stone cold...start it up and walk around to the metal trans cooler lines that go into the radiator. grab one and feel it. By the time you walked around to that line and got your hand on it, you can feel the warmth of the fluid starting to build ! it only takes seconds for the heat to build since its being generated regardless of the trans working or not...its still forcing fluid thru orifices to have that power necessary to make things happen how and when you want it to happen.

if you say your engine temps were under 200 and the trans was a little over that, then I'd say that all was near ok as far as heat goes.. Because....the radiator must be cooler than the trans fluid so there is a heat differential for heat exchange. The fluid should not be boiling, but it is probably close. Once the sting of a trans rebuild is felt, adding an extra oil cooler is often what happens next. I stuck my "extra' trans cooler in the nose in front of the a/c condenser and tapped the existing fluid lines to send the fluid thru the radiator, THEN thru MY cooler, then back to tank (trans pan). I also run synthetic fluid, and so far so good.

However, your trans slipping and acting up when "hot" is not good. Something is definitely not right inside the trans. Its a sad fact but these things (trans) as semi-maint-free as they are, sooner or later will simply wear out. The trans is probably the one thing on any car that does so much work and requires so little attention. Check the fluid once in a while, change it every few years and its happy. No other major piece of a car ask so little and does so much..
You stated that your fluid was clean and not burnt, fresh filter and fluid. Yet slipping WILL cause a burnt smell and a darker color to the fluid...
IIWM, I'd check the shift linkage first to make sure it was actually fully in whatever gear the selector is showing. If the linkage is not completely getting the trans in whatever gear, it CAN and WILL slip in/out and almost act like its between gears. The control valve is unable to close that port that's directing oil to actuate that particular gear. Next time it starts the slipping, move the shifter to the next gear or just move it around....if you are in OD shift it to Neutral then back to OD and see if that does not "grab" the gear. I had a similar problem that was kind of sliding out of reverse, or it took reverse 2 to 3 seconds to "grab" when I shifted to reverse...or I had to rev it a little to get it to move in reverse. Scary ! My first thought was Oh Sh*t....new trans time. It was actually the linkage not letting the shift-shaft go fully into reverse position...it was like halfway in reverse. Finally pinned it down accidentally by NOT having the shifter in the rev slot...but 1/2 way between rev and Neu and it worked perfectly ! Linkage adjustment. problem solved.

When a mechanical failure shows up in a hyd system when it gets hot, that's a sign of fluid bypassing control devices, aka slippage. This equates to a pressure loss at the device, causing the loss of control as well. This also starts a vicious cycle of sorts.. Heat causes the slippage to appear and the slippage causes MORE heat as fluid is forced out or thru other places where it is not supposed to be going...heat causes slippage causes more heat. Its a self destruct sequence for a hydraulic system. Once something worn causes this to start, only mechanical repair can cause it to stop.

Check the linkage. You can do that yourself. It might be a simple fix.

It could be many other things, so I'd get on the ph and start calling around to find a shop that does a free diagnostic exam, pressure testing, test drive, etc and get in line !
The sooner you deal with a trans problem the less it will cost you...and I can tell you with some certainty that the cost to fully rebuild a modern automatic transmission is as much, if not MORE than it is to rebuild the engine !

I know this is not what you're looking for, but I wanted to explain the how and why so you could understand the $$ of whats happening.

good luck

 

230° is quite reasonable. One thing that does happen is that the internal pressure in the transmission goes down as the temperature goes up. You have an electronic transmission and the transmission controller tries to adjust the pressure but can only go so far. There are aftermarket kits that can boost the transmission pressures. This helps clamp the clutches tighter and prevent slipping. These kits are quite common and pretty much any transmission shop will know about them.

If you really want to make sure you're going to a high performance trans shop, call TransGo (they do not have online technical support) and ask them for a referral to a transmission shop in your area.

http://www.transgo.com/

 

thanks for the write up Lee
I don't see how it can be the linkage seeing as it works flawlessly when its cool, run it through a canyon in a spirited manner, it starts slipping. I pull over for 5 min and try again and it works till it comes back up

I'll definitely check the linkage though!
And im doing the extra cooler like you did as well

and yea unfortunately im aware of the price of a nice trans rebuild. had a real nice th400 built for my rock crawler im building...but it'll hold 1000 ft lbs of torque haha


And Cliff,
do you think since its electronically controlled, if its just losing pressure due to heat I can have the shift pressures turned down in the program for it? I know they can be controlled and played with.
I'll look at that site

I figure if im gunna rebuild it (if this ends up being the case) id like to run stronger than stock internals. Anything on the market for these?

 

To add a cooler similar to what I did...

its as follows......

I laid a section of aluminum C-channel on the bottom of the lower shroud in front of the condenser where I wanted the cooler...about 3" ahead of the condenser was all I could get. The cooler was 14" wide...so the space was limited. It needs to be in front of the condenser so there is room for fresh air to pass to the a/c or that suffers.

I riveted the C channel upside down to the plastic 'floor' the cooler then rested perfectly down inside the C channel...so it was semi mounted. I then used plastic strap or plumbers tape to hold the cooler down in or on the C channel. One end had a natural spot for the 1/2" wide strap, the other end I went around a cooler tube to the lower shroud floor and secured the strap with small self tapping screws. I also secured the hoses so they did not flop around and pull the cooler down. The whole system is stable and solid.

The lines...
The cooler was mounted slightly to the rt, toward the driver side so there was room for the lines on the left. The steel trans cooler lines are on the left, so that's where I added on some HD trans fluid rated hose and routed it thru a natural opening to the cooler. I also "double bag" the trans cooler hose with heater hose wherever it might lay against something or pass the edge of something that might eventually saw a hole in the hose from vibration. I simply split heater hose and secure it on or around the trans hose with zip-ties at the appropriate place.

Just like the a/c condenser vs radiator....you DO have to clean the trash out from behind the cooler sometimes. Otherwise half the condenser cooling surface is lost.
I WAS worried that feeding MORE heat to the condenser to the radiator would be too much of a build-up of heat, but that never seemed to be a problem. Nothing changed, the a/c still works perfectly as long as there is some air flow thru the condenser, and the trans heat is being dumped off to some degree. How much? Can't say for sure. I DO know that the cooler is hot and when there IS air flow thru there, it HAS to be leaving at least some of that heat in the airstream.
If nothing else, I can honestly say that adding the trans cooler certainly didn't hurt.

I looked at mounting behind the radiator BUT that airstream was already red-hot so that didn't seem like it would be of ANY benefit. I wanted a cooler, not a trans cooker !

While the car is down for rebuild this winter I'm planning on adding a 'chicken wire' screen in front of everything to help keep the air box area with the 3 heat exchangers free of large debris like paper and trash bags...leaves...just gotta deal with those.