Transmission Overheating (1 Viewer)

[M P]

Hey All,

So, when I first got my truck (a little over a year ago) the AT Oil Temp light was coming on during long trips- I was pulling over way too often and letting it idle/cool.

After doing some research here, I had a Hayden 679 external cooler installed. I thought that solved the issue, but on a recent long trip - on a flat stretch of highway no less- the transmission overheated again.

When I got home I had the Transmission fluid changed out, and bought a Transmission Temperature Gauge from Wholesale Automatic Transmissions in Australia and had it installed.

On my most recent trip up into the San Bernardino mountains it was reading over 260 on a long uphill grade. Way too friggin' high.

So my question is - with new synthetic fluid and an external cooler - why is it still getting so hot?

I'm running 33's without a re-gear, but I don't think that accounts for it. Could it be a clogged line/flow problem? Should I take it to a transmission specialist to check the flow?

Any insights/advice would be appreciated, as I can't afford to replace this transmission right now if I fry it.

The transmission shifts great - a little punch going into reverse, but otherwise feels right. The previous owner said he'd had it rebuilt.

M

 

[Michael Hanson]

Hi, Have you dropped the pan and cleaned the filter ? Mike

 

[cps432]

I don't have an automatic transmission so I'm not aware of all the ins and outs of that system, but I have heard that running synthetic oil in the engine isn't the best idea for an old truck. The gaskets and seals weren't designed for the detergents they use in modern lubricants. Maybe it's has something to do with the oil type?
In regards to the punch you refer to when going into reverse, in the manual transmission it helps to put it in second gear and then put it in reverse. I'm not sure why this is but can only imagine it has something to do with getting the gear sets lined up. The reverse gear doesn't have a syncro ring in it because it's assumed that you'll be stopped when going into reverse and there's no reason to over engineer a complicated system.
Again, this is all knowledge coming from the manual transmission.

 

[89BIGBLUE]

Check the soft trans fluid lines for twists, crimps, or bends.
Also check the that the trans temp sensor wiring isn’t tied to or laying on the trans fluid out line on the transmission.
How much space is there between the transmission cooler and the Rad/condenser, depending on where you put it?
Cleaning the screen/filter in the pan is a good idea!

 

[SteveH]

I'm running 33's without a re-gear, but I don't think that accounts for it. Could it be a clogged line/flow problem? Should I take it to a transmission specialist to check the flow?

What heats up the trans is running in a non-locked condition. If your TC is never locking due to a mechanical problem, or big tires and long hills, it will run very hot. So, part of your diagnosis will be figuring out how well this is working. I agree that 260 is way too hot, and you've done all the right stuff up to now. I presume if you aim an IR temp gun at your trans cooler, it shows ~240-250 when the pan temps are 260? You could install a 26 or 31-row Ford Powerstroke truck trans cooler (2001 or later), but fitting it in an FJ60 may be an issue.

 

[Randy88FJ62]

If you don't regear then you need to go really slow up grades and anywhere in general to stay in 4th gear locked up. When you downshift to 3rd gear there is no lock up and you will generate tons of heat.

Options:
1 go slow and stay in 4th gear
2 regear
3 buy extreme valve body from wholesale automatics which has 3rd gear lockup.

There is no easy cheap solution with the setup you have.

 

[RodrigzCrzr]

I would say drop the pan and clean that filter out. And make sure you are at the correct level.