Groan or grunt noise

[mhughes]

After driving through the mountains of Montana and Yellowstone last spring transmission shifting became very erratic. Extremely hard down shifts and flare between gears.

As I approached home, about 800 miles later, shifting got better but far from normal. Decided to change filters. The drained Transynd was far from clear having a slight muddy appearance and an efflorescent sheen. Mileage was 65k. Bought used so I don't know if any prior service had been done.

On the next trip shifting improved greatly after about 800 miles but still an occasional flare and hard shift. Noticed a "groan" or "grunt' between 2nd and 3rd. Fairly pronounced.

Took the coach to the Allison dealer in Coburg who connected a laptop and test drove for about 30 minutes. No codes. Fluid level OK. Did correlate the groan to the torque convert lock up event. Tech suggested a new TCU but had none in stock. Since heading to Salt Lake anyway and they have an Allison distributor there I decided to have another shop take a look.

Salt Lake replaced the TCU, verified fluid levels and test drove another 20 minutes. Tech reported that they didn't notice much change in behavior. Suggested that for another $2k they would pull the control valve assembly and inspect it. As for the groan they said they were not sure of the cause and that torque converter failures were uncommon unless it was a trash truck. Opted to let the issue get worse and headed off to South Dakota.

Groan hasn't changed but shifting gradually got back to normal with only one or two hard shifts and flares.

Any comments or suggestions would be greatly appreciated.

Trans model 3000MH
Mileage now at 67K

[Skip426]

Any chance the noise could be external of the transmission ?

Lock up; particularly in the lower gears, where RPM and engine torque are at their highest ; puts added load on engine/trans mounts , and you could have the motor mount brackets contacting the frame ; bottoming out the mount ; transferring engine vibration to the whole coach.

If you've had harsh shifting issues for a while , the mounts may have sustained some damage.

[mhughes]

The noise occurs only during torque converter lockup event between 2nd and 3rd gears. Heavy or light throttle. Never occurs at any other time or gear.

In Coburg the Freightliner/Allison dealer spend more than an hour on the hoist examining the rear suspension and motor mounts. No issues found other than a slight adjustment of ride height.

[mhughes]

Another odd issue. May or may not be related to current problems. Starter has begun to grind gears. This happens about every 3rd or 4th time I start the engine. Engine usually starts on the second or third try.

[TDT]

Did you ever find a resolution to your trans issue? Our 3000MH has just started doing this. We are currently 1000 miles from home, waiting for Allison shop in Burmingham to open on Monday morning

[mhughes]

Yes, turned out to be plugged filters causing low hydraulic pressure.
A little history.
The transmission had been serviced with new Transend and filters and within 200 miles it started groaning on locking up the inverter (between 1st and 2nd gears) Took it to several Alison transmission shops to no avail. I had asked each to check line pressure and none ever did. On return I removed the new filters and sure enough, they were plugged. After changing them the issue went away. Evidently the old original filters were not filtering at all. when the new filters went in they immediatly plugged up. It has now been more than 20,000 miles and the issue has never returned.

Originally Posted by TDT

Did you ever find a resolution to your trans issue? Our 3000MH has just started doing this. We are currently 1000 miles from home, waiting for Allison shop in Burmingham to open on Monday morning

[jacwjames]

Do you get any fault codes using the shift pad???


Press the up & down buttons twice and if there is a fault code it will display them. See attached!!

[TDT]

Thank you for the update. It is good to know there is a chance that it is not something major. I have tons of maintenance history on this MH, including several engine oil and filter services. But I don't see any reference to a Transmision service. it currently has 74,000 miles on it. So even if it was done on schedule, it is about due again. We have a service scheduled at home for April. I presume it will get one tomorrow.
Operating temps have been in the normal range. The noise does NOT occur when the trans temp is below 100 degrees. The fluid level reads HI. But there are no warning lights or diagnostic codes. Thanks for that document with the list of codes.
I'll let you know what we find tomorrow.

[Elictrix]

An oil level reading of 1 or 2 quarts high is usually not much of an issue. The oil may start to foam if the level is too high.
Not checking mains oil pressure, especially when requested, is a worry. Doesn't install confidence with their ability to diagnose or repair Allison transmissions.

[jacwjames]

How long has the oil level read high?? Is this new??




Since you own a Monaco branded motorhome, not sure what year, there have been reports of the tranny cooler inside the radiator failing and coolant being pushed into the transmission. Last year I had two people contact me with this problem. When that happens the radiator has to replaced, coolant flushed and replaced, and transmission repaired and or replace with rebuilt

[TDT]

Well, it is not good news. The Trans cooler has leaked coolant into the transmission and ruined it. The fluid looks like a strawberry milkshake. Fluid being high is a new thing, and now we know why.
Option 1 - replace fluid and filters and try for home (900 miles). Risky, and does not help much. We still need it repaired. Got a big trip planned for this summer.
Option 2 - Replace the transmission and the cooler. Getting a 3000MH Trans is not a problem, they (W W Williams) can have one here tomorrow. But the cooler for our 2011 Holiday Rambler is an unknown, they are still looking for one, or something equivalent. Once they have all the parts, trans swap takes one day. Cooler swap about a half day (I'll figure on a full day). Gonna put a $14,600 hole in my wallet for the trans. Plus whatever the cooler costs.

[jacwjames]

Yup, this happens more then you would think.



Rebuilt transmission is ~$6500 + install, say $10K




I had a different problem. I bypassed the internal tranny cooler in the radiator and installed a stand alone cooler, just plumbed it into the transmission. I bought one at a used one at at a salvage yard. Works great.

[TDT]

On our 2011 HR Endeavor The transmission has a dedicated cooler mounted on the driver's side with its own fan. That one is fine. The 2nd cooler mounts in-between the radiator and the engine. Radiator fluid runs thru it, but it is not integrated into the actual radiator. That is the one that we need to replace. It looks like a rectangular box about 4 inches by 4 inches by 27 inches.
Does anybody have a suggestion where we can find a replacement?

[jacwjames]

Different then mine



But you might try Radiator Supply House who built radiators and coolers for Monaco, if you remove the old cooler there might be a number on it.

https://radiatorsupplyhouse.com/prod...-215865-725747


Or check with salvage yards.
https://rvparts.visonerv.com/cgi-bin/f/search.pl?