Limp Home Mode

[ga traveler]

We were on our way to Cherokee, NC from Atlanta. Going through Franklin NC there was a long line of cars to get on hwy 441. We inched ahead for a quarter mile or so and finally got on 441. It was hot. Close to 90 degrees. We went about two miles and caught a sudden red light. A modertly hard brake and suddently smoke enveloped our coach. There was a truck with huge mudding tires next to us. I thought the smoke was from his vehicle. We continued on. in a couple of miles we encountered a 8% grade. The coach normally pulls those grades in second at 45 mph. It boggged down and I had to shift to 1st and could barely make 22 mph. I pulled over and stopped. A huge cloud of smoke enveloped the coach. I checked underneath and red transmission fluid was running out from under the coach. It was comming out between the engine and transmission. I knew the front seal had blown in the transmission. I let the engine run for twenty minutes and checked the fluid level. It was still in the lower full range. I disconnected the car and drove home 200 miles with no problems other than smoking a little at each stop. (I was braking very gently.) The smoke was caused by the transmission fluid pouring on to the crossover exhaust pipe when stopping. I am trying to figure out if the reason for the not pulling the grade was the transmission or was the engine in limp home mode. Do you get a code for limp home mode. If you have ever been in limp home mode, did the coach act normal just no power.

[sedaliaterry]

Do you recall the max RPM you were able to hit going up the grade? Usually another clue to Limp mode is not being able to exceed 2k RPM.

[Waiter21]

Sounds like a transmission overheat event and limp mode.. Did you note if your OD light was blinking? I bet it was... You have the same setup as I do.

Our early V10 model F53's (4R100 tranny) were lacking in transmission cooling, particularly, the vehicles engine radiator does not include an integral transmission cooler. The only transmission cooling is from the transmissions cooler radiator. For this cooler to be effective, it must have airflow through it. The lower photo shows the transmission radiator cooler.

The only way to get air flow is either speed, OR, the vehicles fan clutch needs to be engaged to pull air through the radiators. HOWEVER, If your sitting in slow moving traffic, the engine temperature may not be high enough to cause the water pumps fan clutch to engage and if it is engaged, its not turning very fast.. AND, because your crawling along and the torque converter isn't locked up, its generating a lot of heat because its slipping.

Transmission fluid expands, a lot, as it heats up, you were probably puking it out the vent.

My recommendation. If the transmission seems ok now that its cooled down, I'd do this:

• Drop the pan and replace the filter.
• Either delete the cooler bypass tube, or overhaul the bypass valve. I recommend overhaul.
• Add an external spin on filter in the cooling line. (Do this AFTER you flush)
• Flush the transmission, use the cooler return line flush method. I use Valvoline ATF Synthetic. It takes about 5 gallons to do a cooler line return flush.
• If you plan on this driving style in the future, replace the engine radiator with one that has the built in transmission cooler.

If your stuck in traffic, put the trans in "N" so the torque converter isn't slipping. You can monitor transmission temperature with the Torque app. Mine typically hangs about 170 degrees while cruising down the freeway..

I was considering adding a small 7-10 inch radiator fan on front of the transmission cooler. I could turn it on if I'm stuck in a situation like yours.

Here are a couple links you may be interested in:

F53 Transmission filter change and flush – 1999 Southwind 35S


F53 4R100 transmission cooler bypass tube – 1999 Southwind 35S


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[ga traveler]

Originally Posted by sedaliaterry

Do you recall the max RPM you were able to hit going up the grade? Usually another clue to Limp mode is not being able to exceed 2k RPM.

The rpms were about 4000 rpm. I have checked with a couple of mechanic friends and they say it was not in the limp home mode because the check engine light did not come on.

[Waiter21]

The rpms were about 4000 rpm. I have checked with a couple of mechanic friends and they say it was not in the limp home mode because the check engine light did not come on.

The transmission limp mode was initiated by the transmission. This hold the tranny in 2nd gear.. The OD light on the gear shifter serves as the fault indicator for the transmission. I suspect it was blinking at you.

[Kahoona]

Originally Posted by ga traveler

The rpms were about 4000 rpm. I have checked with a couple of mechanic friends and they say it was not in the limp home mode because the check engine light did not come on.

I've been in limp home without the check engine light coming on and that was from a failed fan clutch causing high temps.

[ga traveler]

Originally Posted by Waiter21

Sounds like a transmission overheat event and limp mode.. Did you note if your OD light was blinking? I bet it was... You have the same setup as I do.

Our early V10 model F53's (4R100 tranny) were lacking in transmission cooling, particularly, the vehicles engine radiator does not include an integral transmission cooler. The only transmission cooling is from the transmissions cooler radiator. For this cooler to be effective, it must have airflow through it. The lower photo shows the transmission radiator cooler.

The only way to get air flow is either speed, OR, the vehicles fan clutch needs to be engaged to pull air through the radiators. HOWEVER, If your sitting in slow moving traffic, the engine temperature may not be high enough to cause the water pumps fan clutch to engage and if it is engaged, its not turning very fast.. AND, because your crawling along and the torque converter isn't locked up, its generating a lot of heat because its slipping.

Transmission fluid expands, a lot, as it heats up, you were probably puking it out the vent.

My recommendation. If the transmission seems ok now that its cooled down, I'd do this:

• Drop the pan and replace the filter.
• Either delete the cooler bypass tube, or overhaul the bypass valve. I recommend overhaul.
• Add an external spin on filter in the cooling line. (Do this AFTER you flush)
• Flush the transmission, use the cooler return line flush method. I use Valvoline ATF Synthetic. It takes about 5 gallons to do a cooler line return flush.
• If you plan on this driving style in the future, replace the engine radiator with one that has the built in transmission cooler.

If your stuck in traffic, put the trans in "N" so the torque converter isn't slipping. You can monitor transmission temperature with the Torque app. Mine typically hangs about 170 degrees while cruising down the freeway..

I was considering adding a small 7-10 inch radiator fan on front of the transmission cooler. I could turn it on if I'm stuck in a situation like yours.

Here are a couple links you may be interested in:

F53 Transmission filter change and flush – 1999 Southwind 35S


F53 4R100 transmission cooler bypass tube – 1999 Southwind 35S


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Waiter 21 thanks for your input. I have read many or your past post and have been online with you a few times. I think you are the KING of preventitive maintainance. I was a RV service manager for 15 years. We never worked on transmissions, there was a transmission shop a mile from us and we sent everthing to them. I have some knowledge of transmissions but certainly no expert. According to mechanic friends #1 I was not in limp home mode bacause there was no code set and I was able to drive over 2K rpm. #2 There was no overflow out the filler tube or the vent tube. #3 The front seal is shot. It must be replaced. My plan is to drop the pan and pour the fluid over a paper towel and check the towel for trash. If the pan is clean it is time to make choices. #1 Drop the trasmission and change the front seal #2 Drop the pan and change the front pump. #3 Change the torque converter while in there? #4 Or just go with a rebuilt transmission. I do plan to do away with the bypass tube. I am going with the spacers and removing the tube completly. The number one thought in the transmission techs I spoke to is remove the tube and just warm up the engine and tranny before driving in the winter. I always do that anyway. I always warm up and cool down the engine.

[Waiter21]

SUCKS.......

I'd say that the only problem is the front seal. HOWEVER -- I sure would hate to take everything apart, then a thousand miles down the road, facing the same problem...

With that, I'd probably go for a reman tranny and torque converter... There are some mods that get done to beef it up.

Also consider replacing the radiator with one that has an integral tranny cooler, and also add an external spin on filter.

Did you look at pricing yet?? I thought I seen 4R100's for $2500..

NOTE - Tranny limp mode doesn't set engine rpm. It limits shifting to 2nd gear. no engine codes are set and no SES lights. The OD light will blink.

[Mark Kovalsky]

Originally Posted by ga traveler

#2 Drop the pan and change the front pump.

If this says you're considering changing the pump through the pan, you'll find that this is impossible. The pump comes out through the bellhousing, not through the pan.

Originally Posted by ga traveler

I do plan to do away with the bypass tube. I am going with the spacers and removing the tube completly. The number one thought in the transmission techs I spoke to is remove the tube and just warm up the engine and tranny before driving in the winter. I always do that anyway. I always warm up and cool down the engine.

That's a very bad choice. The bypass has NOTHING to do with warming up the transmission. It has no thermostat and does not bypass when cold and flow when hot, which is how most people think it works. It does not. It bypasses the coolers if the restriction in the cooler circuit gets too high.

The reason this is important is that the return from the coolers is used to lube the rear half of the transmission. If you remove the bypass and something happens to the coolers or cooler lines your first indication will be that the trans fails.

If the bypass is in place and working it doesn't bypass unless the cooler circuit is restricted. If it is restricted the bypass opens and maintains lube flow to the rear half of the transmission.

I recommend installing a rebuild kit for the bypass. You can get one from Summit for about $25. It's really easy to install.

Originally Posted by Waiter21

NOTE - Tranny limp mode doesn't set engine rpm. It limits shifting to 2nd gear. no engine codes are set and no SES lights. The OD light will blink.

That's not correct. There is no limp mode that sticks the trans in second gear. Chrysler did this on their early electronic transmissions. We (Automatic Transmission Engineering at Ford) learned from their mistake and didn't do this to our transmissions.

With any failure we could determine what gears are available and what gears will not work. We use the ones that can be used and skip the gears that won't work due to the failure. That's a lot different than only having second gear available.

[Waiter21]

My Apologies. When I was researching my cooling system, I ran across several statements that indicated the transmission would not shift past 2nd gear in an overheat event.

NOTE - Front seal.. I was thinking about this last night. If the transmission was hot, this may soften the front seal and produce the leak.. Once the transmission cools, would the seals integrity be restored.

Its hard to say what I'd do until this actually happened to me. but I'd consider this:

I'd run the vehicle to see if the leak still existed. Monitor the trans temperature. If it didn't leak, I might drop the pan, new filter, complete flush, and install a additional spin on. Then keep an eye on it.

[ga traveler]

Originally Posted by Mark Kovalsky

If this says you're considering changing the pump through the pan, you'll find that this is impossible. The pump comes out through the bellhousing, not through the pan.

That's a very bad choice. The bypass has NOTHING to do with warming up the transmission. It has no thermostat and does not bypass when cold and flow when hot, which is how most people think it works. It does not. It bypasses the coolers if the restriction in the cooler circuit gets too high.

The reason this is important is that the return from the coolers is used to lube the rear half of the transmission. If you remove the bypass and something happens to the coolers or cooler lines your first indication will be that the trans fails.

If the bypass is in place and working it doesn't bypass unless the cooler circuit is restricted. If it is restricted the bypass opens and maintains lube flow to the rear half of the transmission.

I recommend installing a rebuild kit for the bypass. You can get one from Summit for about $25. It's really easy to install.

Thanks for the information mark. When I said drop the pan and replace the front pump I meant drop the pan and check the fluid for contanimates. If the fluid is red and clean then drop the transmission and change the front pump. The fluid on the dipstick looks good. It is still red and smells like most used fluid. Also, I have been told the filter is plugged into the front pump and must be removed before removing the front pump. Is this correct? I will be rebuilding the bypass valve because of your information. Again thank you for that. My biggest concern is about rebuilding the transmission. I retired in 2005. I am not hurting, but money is tighter because of the rise in cost of living in the last 14 years. I don't want to change the transmission unless it is neccessary. Of course, I don't want to break down on the road either. I still can't figure out why I lost power on a 8% grade. I usually pull these at 45 mph in second. I was only able to make about 22 mph in first. There was no blinking of the overdrive light and no check engine light. The transmission did fine after the 30 minute cool down. I drove home with normal shifting. I had smoke each time I braked for a light, but of course that was the fluid at the front seal leaking onto the crossover pipe. I did pull codes from the OBDII yesterday and got P1703 and P1780. Could either of these cause the low power?

[Waiter21]

I believe the P1780 may be related to the OD switch and light on the gear lever.

F53 Replace transmission shift lever (OD button) – 1999 Southwind 35S


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[Mark Kovalsky]

Originally Posted by ga traveler

I did pull codes from the OBDII yesterday and got P1703 and P1780. Could either of these cause the low power?

Those two codes mean that you didn't press the brake pedal or the OD OFF button while self test was running. Neither one means anything is wrong.

You cal lose power if the engine or trans are overheated. But that should also set a code.

If it were mine I'd rebuild the bypass and check the cooler circuit to see if it is restricted.

[ga traveler]

Thanks Mark and Waiter. The motorhome is sitting on its pad waiting on a call from the garage where I work on motorhomes. I will take it there as soon as they can work it in. It may be a while, but I will let you know what we find. One last thing. I bought my first motorhome in 1974. I had to have a CB. Everyone had one back then. My CB handle was Georgia traveler. I have used that ever since. Where did Waiter 21 come from?