Dear Transmission Gurus. We need help.

Topic: Dear Transmission Gurus. We need help. (Read 1516 times) previous topic - next topic

Dear Transmission Gurus. We need help.

May 21, 2024, 06:04:20 pm

REF: Allison 4000MH

History: Yesterday, May 20, 2024 we traveled from Lewisville TX to Weatherford TX, about 70 miles thru rush hour traffic in Fort Worth. Don't recommend it. Anyway about one exit from our desired exit on I-20 which would lead us to our destination, I noticed the RPMs were high, around 2000. A quick check of the transmission shifter pad and the tranny is in 4th gear.. Why? I try to shift it back to 6th. No response. We pull off the Interstate at our exit which requires a stop at the connector street. Still no change in the transmission shifter. After stopping at the traffic signal, the coach had a difficult time moving. After coasting through the next 4-way stop, we reached our destination. After stopping the coach I could not get the shifter into N. Trans temp was ~ 250 degrees. Not good. Let the coach idle in 4th for a while then turned off the ignition not knowing what would happen. Waited for the transmission to cool down to ~ 220. Turned on the ignition and the shifter is showing N and 6th gear. Yea!! Traveled around the block inside the RV park and found a suitable site which required backing into. After parking I checked the fluid level with the shifter and it indicated four quarts low. Fluid didn't smell burned. Have never noticed any leaks in the past year since we had the trans cooler serviced when the repair facility had to drain and refill the transmission. Wonder where the missing four quarts went?

Today I did a cold check on the transmission fluid level. It was ok enough to move the coach if we needed too.. No burned fluid smell. Checked for error codes on the shifter. Had two. D1: 5443, On coming ratio test after shifting. D2: 6600, Serial Comm Interface Fault.

Having a difficult time locating a transmission shop in Fort Worth. Called the FOT tech support and they referred me to the same places I had found on an Internet search. Called MOT for assistance or advice but had to leave a message with no call back.

Engine batteries and alternator are ok. Plenty of voltage, no check engine lights. Just had MOT in April ensure the battery connections were clean and tight while we were there for annual PM.

Anyone have experience with transmission repair businesses in the DFW metro area they could recommend?

Re: Dear Transmission Gurus. We need help.

Reply #1 – May 21, 2024, 06:10:13 pm

If trying to cool down transmission fluid you need to be in NEUTRAL with engine RPM over 1100.

Using your shift pad, check for DIAGNOSTIC CODES.

What are they?

What is chassis battery voltage when this happens. The Allison ECU acts "stupid" if voltage is too low.

Re: Dear Transmission Gurus. We need help.

Reply #2 – May 21, 2024, 08:25:37 pm

Had two diagnostic codes: d1: 5443, On Coming Ratio Test After Shifting. d2: 6600, Serial Comm Interface Fault. I presume checking the engine battery voltage means using a multimeter on the battery posts? Any other place to take this reading? I have a cigarette plug type voltage meter plugged into the dash cigarette receptacle. Currently it reads 12.82 volts after driving yesterday. I watch this voltage meter while parked and when it drops over a period of days, about a week to 12.5 volts, I switch on the boost for several hours to charge up the engine batteries with the house inverter/charger.

Re: Dear Transmission Gurus. We need help.

Reply #3 – May 21, 2024, 09:56:45 pm

I had a older RV with Allison 3060. It began downrating the trans to continuously lower gears. Cause was defective speed sensor.

"Probably" not your issue, but if it downrates to 3rd then 2nd likely suspect.

Re: Dear Transmission Gurus. We need help.

Reply #4 – May 21, 2024, 10:56:26 pm

The first code means it tried to downshift from 4 to 3 and thinks it failed, so it just stayed in 4. The second, 6600 is communication failure. The only common cause between the two is wiring issues. I would check the harness and see if there is any damage anywhere, Maybe something rubbed or wiggled loose in your trip.

Re: Dear Transmission Gurus. We need help.

Reply #5 – May 21, 2024, 11:37:11 pm

Had you previously checked tranny level? Do you know it was always 4 qt low. 250 degrees can be okay in some situations. Sometimes turning ignition off and later back on clears problems. Always carry a quality volt meter as it is your best friend.

Re: Dear Transmission Gurus. We need help.

Reply #6 – May 22, 2024, 08:22:19 am

Allison Certified

Allison Hub Account

Re: Dear Transmission Gurus. We need help.

Reply #7 – May 22, 2024, 09:28:29 am

Thanks kgrover! We had the Owner's manual in the Files section, but not the WTEC III Troubleshooting manual. It's there now.

https://www.foreforums.com/index.php?media/album/transmission-manuals-allison.203/

Re: Dear Transmission Gurus. We need help.

Reply #8 – May 22, 2024, 12:20:57 pm

I had forgotten about it but this thread reminded me of it. One time a few years ago we were on our way to my FIL's in our U240. After exiting the freeway the RV would barely move. (In Fort Worth by the way) It was stuck in 4th. I was able to make my way into a parking lot and turned it off. Dreading the worst, I did some troubleshooting but nothing obvious was wrong. No codes. When I started it again, the display said N and everything was fine. It never stuck in gear again. Around 3 years later the Allison ECU failed and I sent it to Transmission Instruments to be rebuilt but highly doubt the problems were related.
I realize that you have more going on. I mention this mainly to say that like other things computer related, rebooting may be all that is needed.

Re: Dear Transmission Gurus. We need help.

Reply #9 – May 22, 2024, 09:40:10 pm

Just reading and I was having an issue just the other day coming home to Houston on a flat road, my coach was shifting back and forth between 5 and 6. Going to 6 and downshifting to 5.

Re: Dear Transmission Gurus. We need help.

Reply #10 – May 23, 2024, 08:09:07 am

Quote from: brianefeeze – May 22, 2024, 09:40:10 pm

Just reading and I was having an issue just the other day coming home to Houston on a flat road, my coach was shifting back and forth between 5 and 6. Going to 6 and downshifting to 5.

Diagnostic codes??? Simple to do from the driver's seat. If you need the "how to" it is in your Allison manual, on line or ask us.

Re: Dear Transmission Gurus. We need help.

Reply #11 – May 23, 2024, 09:11:12 am

Quote from: brianefeeze – May 22, 2024, 09:40:10 pm

Just reading and I was having an issue just the other day coming home to Houston on a flat road, my coach was shifting back and forth between 5 and 6. Going to 6 and downshifting to 5.

Definitely shifting (numbers changed) or torque converter dropping out of lockup? They can feel somewhat similar.

Re: Dear Transmission Gurus. We need help.

Reply #12 – May 23, 2024, 09:18:46 am

Quote from: Michelle – May 23, 2024, 09:11:12 am

Definitely shifting (numbers changed) or torque converter dropping out of lockup? They can feel somewhat similar.

And, either one for "unexplained reasons" is cause for concern. And cause to check for diagnostic codes. Let your transmission tell you if it is "unhappy" and, if so, WHY.

Re: Dear Transmission Gurus. We need help.

Reply #13 – May 26, 2024, 10:43:42 pm

Thanks to all who have chimed in on this subject. My contact at Stuart and Stevenson in El Paso pointed me to one of their S&S in Dallas. Suppose to be a much larger facility than El Paso's. Called S&S Dallas and was told "first come first serve", but they would try to work us in as quickly as possible for a diagnosis. The facility is 50+ miles east of us, about an hour and half's drive. The shop opens at 0700 on Tuesday so we'll head out at 0530 with fingers crossed the transmission doesn't "choke" on the way there. Tomorrow I'll drive the rig around the block a couple times to warm up the transmission in order to check the fluid level one last time before heading east on Tuesday morning. There is a gray medal box with a couple of wiring harnesses located in the water pump bay. Looks like some sort of ECU, but don't have a clue whether it is an ECU or if so whether it controls the engine or the transmission???

Re: Dear Transmission Gurus. We need help.

Reply #14 – May 27, 2024, 07:30:12 am

S&S replaced my Allison 4000PRM last summer with an Allison ReTran. If you end up with a ReTran rebuilt transmission it will have a 2 year warranty. That warranty can be extended an additional 2 years, however that extension must be purchased within the first 12 months. It includes towing and any adjustment needed.

Allison ReTran Warranty

ReTran Warranty Pricing

Re: Dear Transmission Gurus. We need help.

Reply #15 – May 27, 2024, 07:58:59 am

Does it look like this? This is the transmission controller. Why it's in the wet bay, I'm not exactly sure. The engine ECM is on the side of the engine. The ABS ecm is in the bay with the inverter and HWH controllers. Why the transmission is hanging out here, by itself is beyond me.

Hopefully your issue is just a wiring problem and you don't need a whole new transmission.

Re: Dear Transmission Gurus. We need help.

Reply #16 – May 27, 2024, 08:32:34 am

Quote from: WagonWheels – May 26, 2024, 10:43:42 pm

Tomorrow I'll drive the rig around the block a couple times to warm up the transmission in order to check the fluid level one last time before heading east on Tuesday morning.

No, it takes many highway miles to get the transmission warm enough to accurately check the transmission fluid level.

Re: Dear Transmission Gurus. We need help.

Reply #17 – May 27, 2024, 09:32:42 am

You can not check for fluid levels until the transmission has reached at least 110 degrees. It will show the last 5 fault codes in memory before transmission is warmed up though.

Re: Dear Transmission Gurus. We need help.

Reply #18 – May 27, 2024, 09:37:34 am

Quote from: DaBus – May 27, 2024, 09:32:42 am

You can not check for fluid levels until the transmission has reached at least 110 degrees. It will show the last 5 fault codes in memory before transmission is warmed up though.

Correct, checking for diagnostic codes does not require driving or even starting the engine.

Just ignition on/key on.

Re: Dear Transmission Gurus. We need help.

Reply #19 – May 27, 2024, 10:25:45 am

Brett: I have provided the diagnostic codes. Ref: Original Post, para 2: Today I did a cold check on the transmission fluid level. It was ok enough to move the coach if we needed too.. No burned fluid smell. Checked for error codes on the shifter. Had two. D1: 5443, On coming ratio test after shifting. D2: 6600, Serial Comm Interface Fault.

Reply 2: Had two diagnostic codes: d1: 5443, On Coming Ratio Test After Shifting. d2: 6600, Serial Comm Interface Fault.

The ECU in my water pump bay resembles the one pictured in the above post. Thanks

Re: Dear Transmission Gurus. We need help.

Reply #20 – May 27, 2024, 11:35:15 am

Quote from: WagonWheels – May 27, 2024, 10:25:45 am

Had two diagnostic codes: D1: 5443, On coming ratio test after shifting. D2: 6600, Serial Comm Interface Fault.

The D2 may be an easy to fix issue. I would get some DeoxIT D-Series page with shop | CAIG or other quality contact/electrical cleaner.

Unplug and using the deoxit plug/unplug/plug the connectors at: Shift pad, Allison ECU and transmission. If communication between shifter, ECU and transmission are not working properly, THAT is the place to start.

BTW, a better diagnostician for Allison ECU/shift pad issues is: Transmission Instruments

That is all he does for a living and actually diagnoses, not just a parts replacer. He is north of the DFW airport.

Re: Dear Transmission Gurus. We need help.

Reply #21 – May 27, 2024, 01:56:35 pm

Transmission Specialties told me to plug and replug any suspect wiring 10 times to help correct any poor connections.

Re: Dear Transmission Gurus. We need help.

Reply #22 – May 27, 2024, 02:23:44 pm

Before I start unplugging and plugging in the ECU and shifter pad should I disconnect the chassis battery?

Re: Dear Transmission Gurus. We need help.

Reply #23 – May 27, 2024, 02:29:39 pm

Quote from: WagonWheels – May 27, 2024, 02:23:44 pm

Before I start unplugging and plugging in the ECU and shifter pad should I disconnect the chassis battery?

Not aware that that mandatory, but, certainly a reasonable precaution. So, yes a good idea.

Re: Dear Transmission Gurus. We need help.

Reply #24 – May 27, 2024, 02:30:25 pm

Quote from: Caflashbob – May 27, 2024, 01:56:35 pm

Transmission Specialties told me to plug and replug any suspect wiring 10 times to help correct any poor connections.

Yup, and same instructions when using DeOxit (right on the can of DeOxit).

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