80 with overheating trans on highway (1 Viewer)

[Hatari]

Hi all. I have a 1992 FJ80 (second owner for around 8 years) which just turned over 200k miles. I had the trans rebuilt about 8k miles ago and other than the harsh shifting (which seems typical on these as they age) it has been good since the rebuild. However, during the last couple of 50 mile hi-way trips the AT overheat warning light comes on at around 40 miles (twice now). Last year I installed a new ARB stock height/extra load suspension which actually lifted the truck about 1 inch. This prompted me to go to 285/75/16 tires (not changing the diff ratios from stock) knowing that an already sluggish 80 would be more sluggish going uphill (which I am prepared to live with). I live in north Georgia, its pretty hilly and I am guessing the 33’s are causing the trans to be a little over worked. I am prepared to install an auxiliary transmission cooler and here is the question: Can I safely bypass the in-radiator trans cooler or do I need to install the aux cooler in tandem with the OEM cooler? My preference would be to install the aux as stand alone but also want the best results and only deal with this once (hopefully). I know this subject may well be covered in the forums but I couldn’t find threads on the topic specifically related to FJ80s. I apologize for the redundant question but any feedback from anyone whose been down this path will be greatly appreciated.

 

[Kernal]

Did the transmission ever overheat before the rebuild?
If so under what conditions?

Was the torque convertor replaced or rebuilt as part
of the transmission rebuild?

Source of parts/rebuild of the torque convertor and transmission?

Was there any other work done on the engine or cooling system since the transmission work??

 

[Hatari]

Did the transmission ever overheat before the rebuild?
If so under what conditions?

Was the torque convertor replaced or rebuilt as part
of the transmission rebuild?

Source of parts/rebuild of the torque convertor and transmission?

Was there any other work done on the engine or cooling system since the transmission work??

The only times the trans overheated prior to rebuild was when I drove up a mountain highway (to about 4k ft. altitude). I took it up there a few times and it overheated every time and I pulled off and let it cool down soon after the light came on. It never overheated on the drive I described in the original thread (about a 50 mile drive on non-mountainous highway) before the rebuild & change to larger wheels/tires.

Torque converter was replaced @ rebuild. All trans seals/o-rings were replaced also. The shop that performed the trans rebuild is local but not specifically focused on Toyota vehicles. They have been in the transmission repair business for decades. I do not know where they sourced the torque converter or other parts.

No engine or cooling system work has been performed since trans rebuild. I replaced the fan clutch about 15k miles ago to address an engine overheating problem. That fixed the engine overheating issue thus far.

As I mentioned in the original thread, I knew going to the larger tires would challenge drivability but I didn’t think that would cause overheating during normal highway driving. It definitely pulls hard at highway speeds (I’m talking 60 MPH or less, I don’t push it hard knowing the limitations of the vintage). I have no issues during shorter runs but also would like to feel confident to drive longer distances.

Thanks for the response.

 

[Kernal]

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[Hatari]

Thanks... Will do,

 

[jonheld]

There's no way that 33s and stock gears will cause an A440F to overheat. Something else is wrong.
It sounds like the torque converter is not locking up correctly at highway speeds.

 

[flintknapper]

There's no way that 33s and stock gears will cause an A440F to overheat. Something else is wrong.
It sounds like the torque converter is not locking up correctly at highway speeds.

This would be by guess as well. 33's aren't the problem...I've been running them on mine for over 20 years and have 330K on the original transmission.

Torque Converter not locking up would quickly generate a LOT of heat and I think @jonheld is on the right track.

 

[Hatari]

This would be by guess as well. 33's aren't the problem...I've been running them on mine for over 20 years and have 330K on the original transmission.

Torque Converter not locking up would quickly generate a LOT of heat and I think @jonheld is on the right track.

Thanks for jumping in. I didn't think 33s would be a problem but it's good to hear from you all that have been running them. I'm looking into having the torque converter replaced along with maybe an aux cooler too just for added confidence. I drive this 80 a lot and would like to be able to do road trips with it so I don't mind dealing with these fixes. I am not sure about the quality or source of the TC that was installed during the fairly recent rebuild but I'll pay attention to the source this time. Thanks again...

 

[jonheld]

Thanks for jumping in. I didn't think 33s would be a problem but it's good to hear from you all that have been running them. I'm looking into having the torque converter replaced along with maybe an aux cooler too just for added confidence. I drive this 80 a lot and would like to be able to do road trips with it so I don't mind dealing with these fixes. I am not sure about the quality or source of the TC that was installed during the fairly recent rebuild but I'll pay attention to the source this time. Thanks again...

The majority of US spec 80 Series came with 2 transmission coolers. One in the lower tank of the radiator and one mounted on the front left in front of the condenser coil just behind the grill.
You might want to make sure both are functional.

 

[Hatari]

The majority of US spec 80 Series came with 2 transmission coolers. One in the lower tank of the radiator and one mounted on the front left in front of the condenser coil just behind the grill.
You might want to make sure both are functional.

I can tell you that my 80 does not have the secondary cooler. It only has the radiator encompassed one. It does have a replacement radiator which was in the vehicle when I acquired it so I don't know if it originally had the second one you reference. But, I'll take care of that when the torque converter is replaced. You've indirectly answered my original question which was should I run an aux cooler in tandem with the radiator mounted unit. Sounds like the answer is yes.

I appreciate all the input on this from all that have responded. I am a decent or better engine mechanic (as a hobby) but I know nothing from nothing about transmissions especially automatic transmissions. I had 4 FJ40s in the 90s/2000s but, of course, all of those had bullet-proof manual trannys so I never had to deal with transmission issues (just a clutch or two).

Thanks!

 

[jonheld]

Below are some pics of the transmission cooler I was referring to. This is from my 1991 FJ80, and my 1997 LX450 is exactly the same.

 

[Hatari]

Below are some pics of the transmission cooler I was referring to. This is from my 1991 FJ80, and my 1997 LX450 is exactly the same.

View attachment 2938633View attachment 2938634

thanks... Like I said, mine definitely does not have this cooler. But, we'll have that taken care of very soon. I don't know if this was discarded when the radiator was replaced (prior to my ownership) or if mine did not have it from new.

 

[flintknapper]

thanks... Like I said, mine definitely does not have this cooler. But, we'll have that taken care of very soon. I don't know if this was discarded when the radiator was replaced (prior to my ownership) or if mine did not have it from new.

They can get pretty damaged over the years. Yours might have been removed for that reason.

I don't how many rocks and birds have hit mine. I finally spent a little time trying to straighten up the cooling fins and clean it up.....but I'd probably have done better to just replace it. My Trans runs cool though....so I guess its doing 'something'.

 

[Hatari]

They can get pretty damaged over the years. Yours might have been removed for that reason.

I don't how many rocks and birds have hit mine. I finally spent a little time trying to straighten up the cooling fins and clean it up.....but I'd probably have done better to just replace it. My Trans runs cool though....so I guess its doing 'something'.

View attachment 2938694
View attachment 2938695

Thanks much for the photos. Hey, if it is running cool, you did good on the straightening! Ive done that too.

 

[woodsman 44]

thanks... Like I said, mine definitely does not have this cooler. But, we'll have that taken care of very soon. I don't know if this was discarded when the radiator was replaced (prior to my ownership) or if mine did not have it from new.

This is most likely your over heating problem..install one and report back

 

[Hatari]

This is most likely your over heating problem..install one and report back

Yes, I am hoping this is the case and fix. Have nothing to lose to install one. Will update once it's on and some miles logged.

 

[Marco Lau]

I have been running 37s, and ran the tranny hard up 7-9k elevation for the past 4 out of 6 yrs on ownership and the A440F is solid, but it does have a tranny cooler and aftermarket radiator cooler tho. Coolant temp is never over 195F even on 4k 2nd gear climb for long duration of time... something is not working right!

 

[Kernal]

Prior discussion of A440F torque convertor locking up:

FJ62 A440F - Torque Converter Lockup

My FJ62 has 315k miles on what I believe is the original tranmission (not entirely sure, though). A few thousand miles ago I did a very thorough flush, added a cooler and temp gauge. I'm fairly certain my lockup is not engaging, as trans temp gradually climbs when cruising on the highway at...

forum.ih8mud.com

another a44Of issue

Hi. Recently my a44Of started slipping when cold,and then wouldn't change out of first until it warmed a bit. Then no overdrive lockup. Fluid level was right, kickdown cable fine. I pulled the pan and the filter was very clean. The fluid was clean too. [ I drain and fill 5 litres every 6 months...

forum.ih8mud.com

 

[Hatari]

This is most likely your over heating problem..install one and report back

OK...Update. Aux trans cooler installed (in tandem with the radiator integrated unit) and trans throttle cable was adjusted to factory manual spec. Prior to this the torque converter lock up was vague or non detectable. Now the TC lock up is evident. Drove it the 40+ miles that had caused the overheating previously today (and ran it pretty hard). No overheating. I think the aux cooler is doing its job (and I do not know why my 80 didn't have this from new) and also think the cable adjustment fixed the ambiguous torque converter lock up. It's definitely locking up now at right around 50 MPH.
Thanks all for your input.

 

[Squash]

OK...Update. Aux trans cooler installed (in tandem with the radiator integrated unit) and trans throttle cable was adjusted to factory manual spec. Prior to this the torque converter lock up was vague or non detectable. Now the TC lock up is evident. Drove it the 40+ miles that had caused the overheating previously today (and ran it pretty hard). No overheating. I think the aux cooler is doing its job (and I do not know why my 80 didn't have this from new) and also think the cable adjustment fixed the ambiguous torque converter lock up. It's definitely locking up now at right around 50 MPH.
Thanks all for your input.

A good way to avoid heat build up is to drop a gear on steep grades, snow or mud. You do not want the tranny searching for gears as the shifting on it's own causes heat.
I run a tranny temp gauge on my HDJ81 and drive according to heat. In snow I have locked her in low just because of the added resistance.