Transmission overheat stumps repair shop

[howdja]

The first of July I took my 2000 Forest River Windsong Ford V10, F53 chassis to a local transmission shop to have the transmission repaired. I was experiencing high transmission temperature (220+) and very rough hesitant shifts. The torque converter was replaced and the tranny gone through in detail. When the job was finished and I took it out for a test drive, the tranny shifted perfect and operated flawlessly....except, the temperature climbed to 229 degrees within 20 miles of driving hilly terrain. I returned it to the shop, researched the internet and found a Ford TSB pertaining to the need to replace the transmission cooler after rebuilding the transmission. This was done by the shop after reading the TSB. The system has been flushed with solvent.

I have found out that the transmission cooling system on my F53 is an "oil to air" process, known as an OTA cooler. It does not use the radiator for cooling, but depends only on the external cooler to cool the oil, which surprised me, as I thought all automatic transmissions used the radiator to assist cooling. After the old cooler was replaced by two new coolers in series, we figured the overheat problem was solved. WRONG.

We drove from Austin to Houson and within 20 or 30 miles the temp was at 240 and still climbing. I was maintaining 65 mph and the temp climbed to 255 degrees. When I slowed down to 55 mph. the temp decreased to 246 +- 4 degrees, but never below 242. We stopped pick up some to go food and after a 10 minute stop, the temperature had decreased to 205 degrees. But as soon as we got back to highway speed the temp climbed back to 245. The ambient air temp outside was 94 degrees. Infrared temperature readings taken on the exterior of the transmission confirmed the high temperature.

Previous readings on the transmission temperature (when it was working properly) were in the 170 to 198 degree range through the western deserts and mountains. Readings are taken from a Scangauge II, and it is properly configured for the Ford transmission. The readings on my Scangauge match the temperature shown on the device the shop connected to the tranny.

The torque converter has again been replaced and the solenoids replaced. There was no sign of the clutches being burned or the torque converter being damaged. The temperature still reaches 210 during a short run.

I have replaced the fan clutch, radiator thermostat, and flushed the radiator to be certain that there is no extra heat being added by the engine cooling system.

I will take the RV out for a long test drive tomorrow over some very hilly roads and see where the temp stabilizes at. Then discuss it further with the shop manager. I have heard nothing but good things about this shop and feel that they do know what they are doing, so I do not think that it is the result of shoddy or amateur workmanship. I have researched the internet and even contacted Ford (was unable to get any help from Ford) to see what info I might get. No solutions yet.

If anyone has any ideas, i would appreciate any and all suggestions. Both the shop and I are getting very frustrated with the situation. Hopefully my test drive tomorrow will result in lower temperatures in a more acceptable range. I would settle for around 210.

[Cat]

It sounds like the lock up clutch is not locking up. You should be able to put a gauge and check lockup clutch pressure. When you are up and moving the transmission should be in direct drive( just like a manual transmission) no converter slippage. If the lockup clutch is not engaging and/or locking up(maybe low clutch pressure) then your transmision oil will get hot. Its my best guess. Good luck.

[howdja]

Originally Posted by Cat

It sounds like the lock up clutch is not locking up. You should be able to put a gauge and check lockup clutch pressure. When you are up and moving the transmission should be in direct drive( just like a manual transmission) no converter slippage. If the lockup clutch is not engaging and/or locking up(maybe low clutch pressure) then your transmision oil will get hot. Its my best guess. Good luck.

Thanks for the suggestion. I"ll ask the shop about that tomorrow.

[Sammie]

Is there any way of checking the temperature gauge and/or sending unit? If you are using the stock dash gauge, it could have gone bad.

Sammie

[Family Time]

As CAT mentioned, a converter not locking up or staying locked will generate excessive heat. Some times a bad throttle position sensor or brake light switch can cause this.

[howdja]

Originally Posted by Sammie

Is there any way of checking the temperature gauge and/or sending unit? If you are using the stock dash gauge, it could have gone bad.

Sammie

I used a hand held infrared temperature sensor to read the outside temp of the transmission and it also read 255 degrees. As a result, I believe the sending unit from the tranny and the gauge is correct. I don't have a dash gauge for the tranny temp,so I use the Scangauge function to monitor tranny temp. Thanks for the suggestion.

My test drive may be put off for a few days, due to low ambient temps and rain caused by Tropical storm Hermine. We're supposed to get hammered with rain here in the Texas Hill Country.

[94-Newmar]

Try to determine where the temp sensor is in the plumbing from the trans to the cooler(s). If the temp sensor is on the outlet from the transmission to the cooler then your temps are not out of line and will be substantially higher than if your sensor is in the inlet side from the cooler back to the transmission.

Reading the temperature of the transmission case is not accurate since there are so many other factors making it heat soaked by being bolted to the engine, exhaust manifolds etc etc.

I like to run two gauges, one on the inlet and one on the outlet so I can see the temperature drop through the cooler(s). That is a good litmus test for a plugged cooler or filter.

Expect a 40-50 degree drop through an average sized transmission cooler under normal conditions.

[howdja]

Originally Posted by 94-Newmar

Try to determine where the temp sensor is in the plumbing from the trans to the cooler(s). If the temp sensor is on the outlet from the transmission to the cooler then your temps are not out of line and will be substantially higher than if your sensor is in the inlet side from the cooler back to the transmission.

Reading the temperature of the transmission case is not accurate since there are so many other factors making it heat soaked by being bolted to the engine, exhaust manifolds etc etc.

I like to run two gauges, one on the inlet and one on the outlet so I can see the temperature drop through the cooler(s). That is a good litmus test for a plugged cooler or filter.

Expect a 40-50 degree drop through an average sized transmission cooler under normal conditions.

I am not sure where the sensor is located. I am comparing the previous temperature reading and range I experienced when the transmission was working properly, prior to repair (170 t0 200) to the temperature I am now experiencing since repair, which is some 55 to 85 degrees higher. So, if my readings differ that much, and the sensor is still the same, I feel the temp readings are way too high. What temp do you read on the outlet from the tranny? Are they in the 250 degree range? I only used the hand held infrared thermometer to doublecheck the reading I am getting, trying to rule out a defective sensor or Scangauge. From what I have been able to determine through extensive searches on this forum and rv.net, and the internet, the normal operating temps are in the 170 to 200 degree range.



I've talked to the shop this morning and they said they were going to do some more research on the problem.

Thanks for your input.

[94-Newmar]

Traveling on mostly level ground, no TOAD, 62-65mph I'll see ~190 on the inlet side and ~235 on the outlet side. I missed your paragraph in the initial post about the temp being OK at one point in time, apologies. That being said then I agree you most likely have a problem somewhere.

Some other things mentioned:

Converter Slippage or Non-Lockup - I really don't think this is the issue. If it was not locked up you would be 500-750rpm higher in high gear on the highway than normal - I think you would notice this. What RPM is the engine running at 65mph?

Bad Sensor: You've obviously confirmed readings with the ScanGauge as compared to what they were before you were having this problem and now, with the problem.

My only other guess is a blockage somewhere in the cooling system OR internally in the trans. As mentioned above, a quick pressure test would determine a bad/weak front pump, plugged fluid lines or cooler, or perhaps a plugged passage in the valve body or internally in a galley somewhere within the transmission itself. Sounds like most everything has been replaced except the transmission housing/case. I'd almost bet something is plugged up internally.

[mpaton]

Have you tried pointing your handheld IR meter at the transmission cooler? You should be able to determine if the fluid flows up/down or left/right, and be able to detect the temperature gradient.

[howdja]

Originally Posted by 94-Newmar

Traveling on mostly level ground, no TOAD, 62-65mph I'll see ~190 on the inlet side and ~235 on the outlet side. I missed your paragraph in the initial post about the temp being OK at one point in time, apologies. That being said then I agree you most likely have a problem somewhere.

Some other things mentioned:

Converter Slippage or Non-Lockup - I really don't think this is the issue. If it was not locked up you would be 500-750rpm higher in high gear on the highway than normal - I think you would notice this. What RPM is the engine running at 65mph?

Bad Sensor: You've obviously confirmed readings with the ScanGauge as compared to what they were before you were having this problem and now, with the problem.

My only other guess is a blockage somewhere in the cooling system OR internally in the trans. As mentioned above, a quick pressure test would determine a bad/weak front pump, plugged fluid lines or cooler, or perhaps a plugged passage in the valve body or internally in a galley somewhere within the transmission itself. Sounds like most everything has been replaced except the transmission housing/case. I'd almost bet something is plugged up internally.

I don't recall what the rpm's are at 65, but they did not appear to be any different than normal. The tranny shifts good and does not appear to be slipping. The torque converter has been replaced by the shop a second time and the internal plates inspected. There was no sign of damage, no blistered paint or burned clutches. They had flushed the tranny thoroughly and replaced the coolers. I had inquired about the temp bypass tube and they said it was OK. An interesting note on our return trip from Houston, and that is we went through a significant amount of rain which dropped the air temp by about 18 degrees to 80 , but the tranny temp remained at around 245 @ 55 mph. The pressures have been tested and were within normal range. I even programmed the Scangauge to monitor the torque converter pressure and the shop said the results were again within normal ranges.

Strange problem, seems that with everything that has been replaced, the problem would have been solved. If I did not have a Scangauge connected and routinely monitored temps, I wouldn't notice anything wrong with the performance of the tranny. But I do know there is a problem with the heat and do not trust the tranny performance on a long trip.

[howdja]

Originally Posted by mpaton

Have you tried pointing your handheld IR meter at the transmission cooler? You should be able to determine if the fluid flows up/down or left/right, and be able to detect the temperature gradient.

I have, and it confirms the high temperature. In addition, the high trans cooler heat causes the air temp flowing through the condenser and the radiator to be significantly higher which affects the water temp (raising it above normal) and the efficiency of the dash air.

[mpaton]

Originally Posted by howdja

I have, and it confirms the high temperature. In addition, the high trans cooler heat causes the air temp flowing through the condenser and the radiator to be significantly higher which affects the water temp (raising it above normal) and the efficiency of the dash air.

Confirming the high temperature is good (for diagnosis anyway) but if the IR temperature of the transmission is the same as the hot side of the cooler AND the cooler side, then you have narrowed down the problem significantly.

If the hot side is very close in temp to the cool side, then you have no cooling air through the cooler. If the temp difference is very large, then insufficient fluid flow through the cooler.

If today's rain didn't make any difference, then you may have a cooler issue. Are you in Austin?

Michael

[howdja]

Michael, i am close to Austin, In lago vista.