BAC Forum
General Boards => Technical Support => Topic started by: Mike Grevers on December 29, 2022, 11:44:07 PM
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Hello Everyone,
I have a 2003 Beaver Patriot Thunder 505 C12 with a Allison 4000 transmission. 38k miles.
Yesterday I took it out for a dive in the first time in 9 months. The transmission shifted extremely hard from 2nd down to 1st. To the point that I coasted through most stop signs in second to keep from breaking anything. I got it home and this morning took it to a Peterbilt dealer that had worked on it for me prior. They called this afternoon and said that the transmission likely had a torque converter issue but that they where not an authorized Allison shop and said I should take it elsewhere. They also did not want to charge me the diagnostic fee which gave me the uneasy feeling that they did not completely understand the problem.
The other shifts where hard as well but did seem to improve slightly as I drove it.
History:
1. The battery had died about 5 months ago and I had to jump it to start it.
2. The trans fluid has not been changed since I have owned the coach (4 years) and likely has not been done in 15 years.
3. The drum brakes where stuck about two months ago and I had to rock the coach to get them to free (should have gotten out with the hammer instead)
I ordered the filters and transynd and will be changing it this weekend. The fluid level is 1/2" high on the dipstick but the fluid looks golden like it should.
I have hear that upon losing power they have to relearn and the relearn procedure calls for WOT shift ETC... I don't think I am comfortable in any WOT shifts with the state it is in and I don't want to cause even more damage.
I am leaving for Florida next friday and I am wondering if anyone here has had a similar issue.
Thanks,
Mike
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Mike,
My understanding is that the Allison 4000 is "learning technology" transmission. It learns your driving style to adapt to the best quality shifts. When the chassis battery is disconnected, the transmission ECM erases the memory it has accumulated concerning shift quality. The transmission has a "default" shift program to get you going however it is harsh after being used to the previous quality. Page 28 on the owner's manual has suggestions to adapt shift quality. Just driving the coach will do the same thing however it may require 20 to 30 miles to program the ECM and you will notice the difference. Fred
P.S. The transmission has to be at operating temperature to Learn.
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I seriously hope that is it. I will drive it for some time this weekend after an oil change and update.
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Mike
The Allison transmission troubleshooting manuals are in coach assist.
When you change your trans fluid use the procedure in the manual to check fluid !evel with the shift pad don't rely on the dip stick as they are notoriously inaccurate.
Remember that the trans has to come to temperature before the system will give you a trans level reading.
You may also want to follow the procedure to check for any stored fault codes.
Eric
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Mike,
Try running it in Economy Mode. I have found that the transmission will shift easier at a lower RPM when in Economy Mode. Hope this helps.
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Thanks to all,
I did try economy mode yesterday and the trans did shift slightly better. I did read about checking the fluid level from the push button shift selector so I will do that after the fluid change rather than rely on the dipstick.
Thanks for the help and I will report back with what happens.
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I changed the trans fluid tonight and filters. NAPA # 7741XE and 7 gallons of Transynd.
The Transmission showed 6 quarts over filled when i took it home from Peterbilt today but I only drained 7-1/2 gallons from it. I filled it with 7 gallons and it showed OK after multiple shifts from reverse to drive and back to neutral. I will take it for a drive tomorrow and see how it does and post an update.
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So the story went sharply downhill from here. I took it for a test drive yesterday for about 2 hours. The transmission shifted alright in the beginning but the longer I drove the worse the shifts got. Highway temperatures started climbing to 225 which is high for this particular bus at 40 degrees outside. That is the temp I typically see around town not on the highway. So I drove it back home and checked the fluid again from the keypad. Now it showed 6 quarts low.
I go to the back of the bus to add the six quarts open the rear access and see that the coolant sight glass for the engine is now yellowish and opaque. So here we go.
I removed the intercooler, hyd. oil cooler, and radiator. I pressure tested the oil cooler in the radiator and found it leaking. I cut the cooler out of the radiator. I cut the cooler open and found no way to repair it. I removed the cooler and welded the plate back into the radiator. I reinstalled everything and luckily had another oil cooler laying around from an old tow behind air compressor. I extended the original lines and installed it in front of the intercooler. Now I will flush the engine a few times and see if all is good. If someone can advise on how to use the images button I will upload so pictures of the repairs.
My advice to anyone that ever has this issue. DO NOT remove the radiator and try and repair it. In hindsight I should have simply removed the trans cooler hoses, plugged the ports, and installed the aux. trans cooler. This would have saved over 10 hours of work at this point.
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Mike,
Sorry to hear of your difficulties. Main concern now is water/coolant in transmission. Small amounts in transmission can be detrimental to life of transmission. Know you just replaced fluid, but might be wise to dump fluid in pan and lines to trans cooler. Not ideal, but at this point probably your best option moving forward. Good luck.
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Thanks,
I agree. Allison calls for replacement of all frictions if they are contaminated with coolant and in the perfect world that is what I would do. I did remove the trans cooler lines and flush the new cooler. I also as you said changed the fluid again. I am going to run it as is with new fluid and see how it does. I guess I’ll be the next persons Guinea pig. I plan to change the fluid again after the next 1k miles. I will post an update after the next long drive I take.
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Mike
Watch you trans temperature's till your next oil change
The reason Allison calls for friction material replacement is that antifreeze will deteriorated the glue that holds the friction material onto the clutch plates causing the material to come loose causing transmission failure.
How much antifreeze did you get out of the trans when you drained the fluid ?
Let's hope you caught it soon enough
Good luck
Eric
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I envy your mechanical abilities tackling this yourself. It’s above my pay grade ;) . But perhaps I can help with your posting of pix.
Mike, go to the Forum’s Home page (see tab above left of this page). Scan down to click “Forum Assistance” (Members Only)”. There you’ll find a Guide and advice for posting photos here. Generally it comes down to whether you’re using Microsoft/Android or Apple based hardware, but it’s easier these days than it used to be. Be sure that you tap the “Reply” button at the bottom right of the last post and NOT the “Quick Reply” that has no option for adding imagery. Underneath your Reply field is a button for adding attachments, but if I recall you need to have entered some text, however minimal, in the field before it will allow attaching anything.
What trips up a lot of members here is the 300 kilobyte (kb) limit per image:
“Restrictions: 10 per post, maximum total size 5000KB, maximum individual size 300KB”.
So on some devices you might need to use an app to downsize each photo to less than 300kb. Others have built-in easy means of downsizing. Check the above mentioned Guide. Or give us info re. what specific device you’re trying to use and one of us should be able to help.
I’m old school and use preferably one of our several iPads to take, downsize, and send pix, or one of our digital cameras. I have an Android phone but as an amateur photographer I don’t like using it for pix due to quality and control limitations. On my iPads the app I use is “Image Compress and Resize Easily” by DKit. I like it’s slider mechanism for knowing exactly how many kb I’m moving to, and can shoot for just under 300; most apps aren’t that simple. Once I’ve got the modified image saved in my device (and iCloud), I delete the original to avoid confusion should I need to reuse it here in the future. On some devices you can set a limit on size prior to taking the photo, but I like starting with maximum resolution quality and working down and rechecking to make sure necessary detail remains upon posting here.
Joel
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Mike
Watch you trans temperature's till your next oil change
The reason Allison calls for friction material replacement is that antifreeze will deteriorated the glue that holds the friction material onto the clutch plates causing the material to come loose causing transmission failure.
How much antifreeze did you get out of the trans when you drained the fluid ?
Let's hope you caught it soon enough
Good luck
Eric
Hi Eric,
Prior to figuring out the cooler issue I had just changed the fluid for the hard shift problem. I drove if for some time after and the trans ran low so I ran home to find the oil in the antifreeze. I assume the trans cooler runs at higher pressure than the cooling system so there should have been no ingress of coolant into the trans until the engine was turned off which makes the trans cooling system 0PSI and the engine cooling system at whatever it was at. At this point the coolant would enter the trans.
When I figured this out I had the drain plug out of the trans within 20 minutes.
I let it drain over night as I had to repair the cooler in the radiator. After that I refilled with 7-1/2 gallons and test drove it today.
I ran it for 1-1/2 hours. At first on highway the trans ran at 158 degrees. At the end of the trip is stayed steady at 147. This is substantially lower than when I had used the in radiator cooler. The one concerning thing is at highway speeds the only thing that would account for the first 30 minutes being at 158 and the remainder of the trip being at 147 would be slippage. Since the temps dropped toward the end of the trip I assume the slippage decreased or stopped.
Here is how I look at it.
I can rebuild the transmission now and it does or doesn't need it.
I can rebuild the trans later because it starts to slip and fail.
Either way I have to rebuild the transmission but option 1 has a chance (no idea what percentage) of not needing a rebuild.
Fingers crossed I caught this in time.
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Please don't be harsh on my aluminum TIG abilities. I am a plumber and not a welder. And IT DID NOT LEAK....
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Mike, very nice, I wish you the very best. Fred
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Thanks, I hope it lasts. Only time will tell and I will be sure to update everyone if it doesn’t or does.
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Mike
I would agree with your assumption the higher temps a first would have been slippage and the TCM would have been trying to counter that slippage by increasing clutch pressures and cutting down on clutch over lap time to decrease the possibility of slippage .
As you drove the coach with fresh fluid in it the clutch packs would eventually Purge the contaminated fluid from with in the clutch packs and the slippage would decrease the TCM would then start to return the shift schedule to a more normal ( less harsh) shift pattern .
By the way if the slippage gets out of control in any one gear the Allison TCM will command a down shift in an attempt to save the transmission.when the slippage gets out of control the TCM will also log a code for that clutch pack stating the slippage issue.
My coach uses a separate trans cooler that is mounted in front of the cooling stack ( first in line before the charge air cooler)
My trans temps run after a hundred miles or so at 148* and when climbing hard for extended periods of time will climb to 158*
And that may be due to RPM lose and related cooling fan lowered air flow through the cooling stack as the coolant temperature also increase from 188* to 196* when extended climbing so i put it off as normal.
It has worked this way ever since I got the coach 4 years ago
I'm with you on this one at this point the end game would be a rebuilt trans and you really have nothing to loose ( except maybe a tow bill if you get stranded)
Hope this helps
Good luck
Eric
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Update:
I took the coach on a trip from Chicago to the Florida Keys for about the last month. The transmission did well. I saw temperatures ranging from 155 to 185 from flat Indiana in the cold to the hills in southern Georgia. Although I got over 2000 miles out of the transmission, it was always in the back of my mind that it's when it will fail not if it will fail. I decided upon my return this past weekend that I will be ordering a reman transmission. I got a few quotes from $10,250.00 at the high end and the lowest at $7,900.00. I will be going with the lowest as they are a major local Allison distributor I have worked with and have a 2 year unlimited mile warranty. Just wanted to let everyone know how it went.
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Wow,
“when it will fail not if it will fail.” That’s just about every major component on the coach. Traveling several thousand miles with zero issues with transmission, I think I would hold off on replacing transmission. There are no guarantees that a rebuilt or remanufactured trans will be any better. Just my humble opinion for whatever that’s worth. Good luck on your decision.