Allison 4000MH S/N 6610110197 Transmission Overheating

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Allison 4000MH S/N 6610110197 Transmission Overheating

April 25, 2023, 07:19:17 pm

Background: We were in El Paso this past winter and it was time to have a total transmission service, i.e., change the trans fluid and all the filters. We took the rig to Stewart & Stevenson to have this maintenance done. The trans fluid they used was TRANSYND 668 and they charged me for 10 gallons. In Feb we departed El Paso for Nac for other maintenance issues and a windshield replacement. While in Nac we noticed some coolant drops on the driveway. We had had the cooling system flushed at MOT about a year earlier. This caused the cooling system to leak so the mechanic put in some stop-leak. This pretty much solved the leaking, but on occasion we would observe some drips over the next year. Well, in Feb the mechanic added a couple more units of stop-leak. After this treatment no more leaks have been observed.

Problem: After leaving Nac we traveled west thru El Paso, Tucson, Phoenix and on to Las Vegas. On the trip from Phoenix to Las Vegas we noticed the transmission temp reading on the high side, ~ 225. The coolant temp was ~ 180 and the ambient temp was in the 70's. We parked in Las Vegas for four weeks. We did some research on high transmission temps. First thing to check was low/high fluid levels. Checked that on the transmission gear selection pad. Read out was normal, fluid OK. Took the rig to W W Williams in Las Vegas for a quick look see just prior to departing Las Vegas for SoCal. They hooked up a computer to the J1939 connector and the computer reported the fluid level as OK, however there was an error code about the wiring. Uh oh!! Could be simple or could require taking apart the transmission. Yikes!! Luckily it was a wire going into the retarder on the outside that had been rubbed. The technician repaired it and the code cleared. Yea! All is well. But wait a minute Sparky, all is not well. We departed LV headed south on I-15 and the transmission temps were in specs. Ambient temp is 80 to 85. BTW we are pulling a 2016 Chevrolet 1500 4X4 pickup truck. Just past the NV/CA state line there is a steep uphill grade. Shifted to third with RPMs at 2000 and got in the slow truck lane. The engine coolant didn't budge from 180, but the transmission temp rose to 225-230. Crested the hill and now we are facing a downhill 6% grade. Can't remember the gear we were using, 3rd or 4th without using the retarder, RPM 2000. Stopped at the rest station at the bottom of hill because the transmission temp was now around 240. Waited for the transmission to cool to 220 then we were off again. Another hill and downgrade into Baker and then up hill out of Baker. We are watching the BlueFire temp gauge and it was reporting 230. 230 isn't good but it's doable. Then we realize the BlueFire unit has frozen and is not reporting. A quick look at the dash shows the transmission gauge reporting 250!!!

Luckily there is an exit just up the road where we pulled off to let the transmission cool down while we unhooked the truck. Without the additional weight of the truck the transmission temp reads at 225 all the way to the Cojon Pass just south of Victorville. Shifted into 4th (RPM 2000) and without using the retarder maintained a safe downhill speed, but the transmission temp shot up to 250 by the time we got to bottom. Pulled over for a rest until the transmission cooled to 225. Off again for the remainder of the downhill decent into San Bernardino where we had to use the emergency lane for yet another stop for cool down. Another 20 miles to go, will we make it? $:-\$ We were able to make it to our campsite at March ARB in Riverside/Moreno Valley without exceeding 230. During all this drama the engine temps never rose above 200. Did a sniff test on the transmission dip stick this morning after the rig sat all night. It didn't smell burned which is good.

Speculation: Any ideas on what the problem is? Could the stop-leak have plugged up the transmission cooler? It didn't diminish the performance of the radiator. Something else?

Thanks in advance for your thoughts and expertise,

David

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #1 – April 25, 2023, 07:46:08 pm

If you didn't shut off the retarder and were using your brakes that's where the heat came from
going down hill as the retarder comes on with the brakes. I believe you can go to 250 with the 688 with no problem.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #2 – April 25, 2023, 09:04:08 pm

Wasn't using the retarder; had it turned off. Used brakes sparingly.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #3 – April 25, 2023, 09:24:04 pm

You had the switch turned off? The is a switch to the back of the Joy Stick the needs to be turned off so
the retarder won't come on with the brakes. I can't see any other reason that the transmission would heat
up going down hill.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #4 – April 25, 2023, 09:39:04 pm

I wonder if the solenoid on the retarder accumulator is stuck open

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #5 – April 25, 2023, 10:12:12 pm

Maybe check the trans fluid for metal particles. It's a long shot but my 03, 38ft, had an issue with brass bushings that showed heat damage. My symptoms were slow heating of the transmission. The longer I drove, the higher the temp climbed. Tried many things at 3 different shops before pulling the pan and found brass particles. Good Luck.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #6 – April 26, 2023, 12:32:14 am

So on your blue fire you can select to read both trans temp and retarder temp. If you are not using retarder they should read nearly the same. This also could be an indication issue and it's not actually overheated. I would take the pyrometer I carry for tires and brakes and read the trans temperature at the case. Also read the temperature at the transmission oil cooler. It is located coach right side just inside the radiator area. About 8-10 inches in diameter and about 20 inches long. Read the oil and the water exiting the cooler. Will probably be the aft large hose facing aft. The smaller yet still large lines are the transmission lines and they should be similar in temperature. Hope this helps. I would also verify that your fan controller is doing its job. They do fail. I installed a permanent needle valve on the sense line to manually shut off flow to manually ramp up fans at my discretion. Disconnecting the fan controller plug on the rear hitch with the engine at fast Idle should result with fans ramping up to hi speed. Could also try driving with plug disconnected to ramp fans to hi just to test

Hydraulic fan controller DIY

Scott

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #7 – April 26, 2023, 01:21:18 am

Peter - The transmission tech at W W Williams told me the check engine red warning "self destruct" will occur when the transmission reaches 260. Don't want to travel far with the trans at 250 with only 10 degrees between ok and disaster. Never know when the gauge is reading a little low or the next hill will be the straw the breaks the trans.

Bill - Metal particle in the trans fluid, not good. I see you are listing another rig in your signature line. Trade off the '03 with the problem or just needed a longer rig?

Scott - There's a love/hate relationship with the BlueFire. It's good when it works, but sometimes it doesn't work. The unit shows both transmission and retarder temps. When the BF is working I can see the temp rise when engaging the retarder on a long downhill stretch. Yesterday when we started our trip the BF was reporting on all the items I had programed into the unit. About an hour into the trip the BF adapter lost comm with my iPhone which shows my BF dash. When it reconnected the retarder gauge wasn't reporting. The BF trans gauge shows more detail than the dash gauge. Problem I encountered was all the BF gauges froze and would not repopulate. This problem has happened before. It's easy to tell when the tach RMP doesn't change. I have a pyrometer. Wished I had used it to check the trans and trans cooler. Maybe the problem is just the sensor. One could only hope for such an easy fix.

No opinions on the stop leak plugging up the trans cooler? A couple years ago, Anson at MOT showed me a trans cooler that was plugged with stop leak when he was changing out a radiator.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #8 – April 26, 2023, 03:54:37 am

I would get a heat temp gun and try and verify these high temps,take the temp at the accumulator and the pan and see what you get,has anyone actually pulled the dipstick and checked the fluid that way,that would be the first thing I would do.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #9 – April 26, 2023, 09:32:34 am

Quote from: WagonWheels – April 26, 2023, 01:21:18 am

.

No opinions on the stop leak plugging up the trans cooler? A couple years ago, Anson at MOT showed me a trans cooler that was plugged with stop leak when he was changing out a radiator.

So it is a fluid to fluid cooler. With the stop leak on the antifreeze side to have become restricted I would think that the oil cooler side would be unaffected and you would see higher water temps. I know first hand when I relocated the wax controller to the line after the cooler the transmission temps was very slow to recover from retarder use. Regardless I would look into proper operation of your cooling system if nothing else by disconnecting your radiator electronic controller. Yes the Bluefire is wonky for me also and I wouldn't recommend to anyone. I did notice it works better on the older coach settings. Don't remember exactly what that was but was in the initial settings. For the first year of operation my worked as you said and after I changed that setting I now see transmission gear position which was one of my primary desires. I'm still talking to Onegauge about a digital dash and if I can get the Bronco out of my hair I'll start looking into it more. The cooler is made by Racor and I had contacted them about bigger coolers and they are available but are two coach bucks. rocore cooler 5-7102b. Bigger and not a direct fit. Having a more robust retarder to use was and is very desirable to me. Old style is unserviceable but the new one is. Crainman has the newer style I believe. The end caps come off for service. I would think the original could be cleaned. If they fail they contaminate the trans oil with coolant and wipe out the transmission, but I dont recall anyone on the forum having this problem.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #10 – April 26, 2023, 12:58:38 pm

TRANSMISSION FLUID LEVEL CHECK

Drive to a truck stop fueling center. Fueling driveways are normally fairly level. If the transmission temperature is within range, wait at least 2 minutes with the engine running, then proceed with the test. Otherwise, let the transmission cool down while fueling the coach, then proceed with the test.

* Meet the following conditions:
- Ensure transmission temp is between 140 and 220 degrees
- Ensure vehicle is parked on level surface and transmission is in (N) neutral
- Wait at least 2 minutes with engine operating at idle, RPM 500 to 800

* Push Button Shift Selector
- Push the up and down arrow buttons simultaneously

* Observe the display window:
- o,L followed by o,K = correct fluid level
- o,L followed by Lo1 = 1qt low; Lo2 = 2qt low, etc.
- o,L followed by HI1 = 1qt high, etc
- o,L followed by — "fault code" = conditions above have not been met

* Fault Codes:
* 0,X settling time too short;
* 5,0 engine RPM too low;
* 5,9 engine RMP too high;
* 6,5 neutral not selected;
* 7,0 sump fluid temp too low;
* 7,9 sump fluid temp too high;
* 8,9 output shaft rotation;
* 9,5 sensor failure

* Press N on the push button shift selector to return to normal operations

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #11 – April 26, 2023, 07:47:46 pm

I've attached pictures of the parts that may play a part in the transmission overheating problem. Not sure about some of the parts so please help me out here.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #12 – April 26, 2023, 07:51:40 pm

This has helped me

The selected media item is not currently available.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #13 – April 26, 2023, 08:14:43 pm

I thru 4 are fuel cooler, charge air cooler, hydraulic system ( fan and steering) cooler, behind that is the radiator.

Photo #5 is the oil cooler for the transmission, radiator coolant flows thru it, it's a bunch of tubes surrounded by coolant, oil to water.

# 6 is the accumulator for the trans retarder,.

As far as the stop leak is concerned, I've had it in my coach for years, additionally I was a fleet manager for 600 vehicles in a construction fleet and we ran it all of our heavy vehicles and equipment, never had any issues with it stopping up anything, ( old wives tale) it used properly. As someone else said have you actually confirmed the transmission is running that hot? You said earlier you had a string is trouble codes, have they been addressed?

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #14 – April 26, 2023, 09:28:06 pm

Last year when I was changing the fan motor seals I sent my trans cooler out to be cleaned and tested
as it was over 20 years old. I was told it was quite dirty and he said he tested it to 160 lbs. He also said
they don't build coolers like this anymore, so we have good coolers

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #15 – April 26, 2023, 10:05:53 pm

David you may have a ground problem, when we first bought our coach we went to Montana and going over continental divide I stopped twice because engine and trans were overheating. I put the vmspc (silver leaf) on the coach and found out gauges were
wrong. The silver leaf has never indicated anything is getting hot as compared to gauges
Chris

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #16 – April 26, 2023, 10:53:27 pm

WagonWheels. I replaced the trans with an Allison rebuilt unit. The trans was looked at by Allison techs that disassembled it. They found the damaged brass bushings and determined most likely damaged by heat. The oil pan on the trans had been replaced by a previous owner, s/n did not match original. Speculation was that the previous owner probably hit a road gator or other debris and damaged the pan causing a rapid loss of trans fluid resulting in some damage to the brass bushings. Was probably towed to nearest shop where oil pan was replaced and trans filled and sent on his way. Lucky me, many miles/years later the bushings had worn enough to cause the slow heating in the transmission. That's all I know. I hope that with the help of way smarter people than me on this forum, you can determine your issue and get back on the road. Sold the coach 2 years later thinking I wanted to downsize. But here I happily am in another Foretravel, just a little longer.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #17 – April 27, 2023, 02:03:23 pm

Thanks to all for your help in this matter. Reference my post #11 above, image #6. I found a better picture online, see below. The brass connector nipple that connects the solenoid valve to the retarder accumulator is not tight. Don't know what this loose connection does to operation of the accumulator. An air line is connected to the solenoid as well as an electric line. I cannot find anything online on how this assembly actually works. I would guess when the driver pulls/pushes on the retarder joy stick to slow the vehicle this action sends an electrical signal to the solenoid valve which switches on?, off?, the air valve in the solenoid. This action allows compressed air to force transmission fluid into the retarder housing thus slowing the vehicle. Since the connection is loose I can only guess the solenoid valve is not working or partially working. Maybe the loose connection didn't allow the retarder to completely evacuate the transmission fluid thus causing the transmission to overheat? Unfortunately, my BlueFire adapter quit working and I didn't have a temperature reading for the retarder. Comments please?

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #18 – April 29, 2023, 11:28:37 am

Fix the loose connection is my comment,and like we said above,get a heat temp gun or a HVAC thermometer and don't go by the blue fire that may or may not be showing the corect temp and go from there,very simple.

Re: Allison 4000MH S/N 6610110197 Transmission Overheating

Reply #19 – June 15, 2023, 09:07:58 pm

In late May we drove the MC about 20 miles to Colton Truck Terminal, Colton CA, for repair of the transmission oil cooler. It's a downhill drive in heavy traffic. Arrived early Wed and they had the repairs done by late Monday. Nothing like camping for five nights at repair facility with weirdos/homeless persons wondering thru the area. Someone decided they needed our aluminum front platform step more than we did. We had 50amp power and access to water. They have a dump port in the middle of the driveway, but we didn't use it. Service was great despite the location. The job looked straight forward, but was more difficult than it appeared. They had to drain the coolant to remove the tranny cooler. It weights about 50 lbs. After removal they sent it to a radiator repair facility for cleaning. Cleaning took took the most time. The radiator repair place said the cooler was very dirty and it took three times in the "bathtub" to get it cleaned and then it had to be pressure tested. Monday the mechanic put the unit back on the rig and replaced the transmission oil. It was pretty "cooked" on our 250 mile trip from Las Vegas. On our drive back to the campground which was uphill, the transmission temp was reading 208d when we arrived. A couple of weeks later we took the rig on a test drive of about 60 miles towing the pickup. A hill was involved so it was a pretty good test. Transmission temp on the dash gauge was just above 200d; ambient temp was 72d. We will begin our summer travels in about a week. Hopefully this fix works and we won'f find ourselves on the side of the road. PS The mechanic repaired the air line to the retarder accumulator solenoid I had removed to tighten the solenoid. Retarder is working great now. It actually comes on when I apply the brake. Never had done this in the last 7 years we've owned the coach. Safe travels to those on the road this summer.

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