Community Forums

omingnome · 12-31-2014, 03:13 PM

Hey there - I have a 1996 Frieghtliner MT-55 Chassis with 12v Cummins and an AT545 - The Transmission has been leaking more and more over the past few weeks. We are traveling a lot - it is an old Shuttle Bus by Goshen that my band converted into a tour bus.

The leak is coming from the top of the tranny - I suspect the breather as far as I can tell. The breather is quite loose to the touch (which from what i heard is normal). But when the bus is parked and I have a friend shift into D and R I can see fluid bubbling up from the breather.

First gear has been a bit rough when the fluid is even a little low - causes a 'stuttering' / 'jolting' feeling when coming from a stop.

I cleaned off the entire transmission and then applied spray on foot powder to see if there was any other leaks - and it seems like it is only the breather - especially when in motion. As we only have a very small puddle of ATF on the ground after a night of being parked and we have had to add a full quart at times just to get it moving.

WE have gone 6,000 miles from Savannah to NYC to Monterey, California where we are now. Been through mountains and some serious climbs (of course we avoid mountains as much as possible now)

We replaced the internal and external transmission filters before leaving.

What can be done to stop this leak / what could be the cause for the breather to be spitting so much ATF (we are using DEX III)

Elictrix · 12-31-2014, 05:44 PM

You haven't over filled it have you?

What is the oil level on the dipstick, with transmission hot, idling in neutral on flat ground?

05kstar · 12-31-2014, 06:00 PM

As was previously stated,it sounds like it is overfilled.Check the fluid level with the engine running and on level ground.It may be necessary to get the part number on the dipstick and verify it is correct for your application. The top of the breather should turn freely.Hopefully no one has worked on the trans. Cooling lines and reversed them,as this can cause fluid to be pushed out the breather.

MartinP · 01-03-2015, 08:39 AM

Not sure why the fluid is coming from the breather if the level is correct. I think if the level is to high you can get foaming. I do now that the fluid level tends to rise in the pan at shut down due to oil draining back. As far as the harsh shifting, I did have a AT 542 and experienced harsh shifts. For me the cure was remove the pan, replaced both internal and external filters and switched over to synthetic fluids. Look for a publication on the internet called Allison AT540 Mechanic tips and hints. You should find a free download.

Martin

hzjcm8 · 01-07-2015, 04:38 PM

Could be the pan filter is loose in the pump inlet and you're sucking air. This would cause the fluid to foam and spit. Also, the fluid may be too thin which would exacerbate the problem.

omingnome · 01-11-2015, 04:15 PM

An unfortunate update :

The past few days the transmission has been extra strange - slipping harder in first and yesterday we lost reverse. - which led to a $125 tow to be pulled 5 feet backwards so we could go forwards.

Looks like we are taking it to a shop - unfortunately we are far from home in Savannah, GA where we have a great, trustworthy mechanic - we are currently in Los Angeles, CA -

Does this sound like the transmission and torque converter are going to need to be completely replaced or does this sound like we could find someone to address the particular issues.

Our mechanic back home said that he would estimate a 4 hour job adjusting the bands for the reverse gear - but also admitted he would really need to by looking at the transmission with the pan off.

Any help would be really appreciated as we are bringing our RV to a shop in the morning and are fearing being ripped off - and as musicians - funds are comically low.

Anyone have any suggestions to a good mechanic / shop in the Los Angeles area that would not require us to travel up any crazy hills?

Thank you!
Tyler

If you feel you could lend a direct hand or advice - please call or text me at Eight 6 2 - Four 3 2 - Zero 7 4 2

omingnome · 01-11-2015, 06:33 PM

Quote:

Originally Posted by hzjcm8

Could be the pan filter is loose in the pump inlet and you're sucking air. This would cause the fluid to foam and spit. Also, the fluid may be too thin which would exacerbate the problem.

Granted we end up not totally replacing the transmission - would you recommend 15w-40 as some people suggest in older at545s?

Also, we did replace the internal pan filter prior to the trip - is this something that commonly comes loose?

Thank you!

hzjcm8 · 01-12-2015, 03:49 AM

Quote:

Originally Posted by omingnome

An unfortunate update :

The past few days the transmission has been extra strange - slipping harder in first and yesterday we lost reverse. - which led to a $125 tow to be pulled 5 feet backwards so we could go forwards.

Looks like we are taking it to a shop - unfortunately we are far from home in Savannah, GA where we have a great, trustworthy mechanic - we are currently in Los Angeles, CA -

Does this sound like the transmission and torque converter are going to need to be completely replaced or does this sound like we could find someone to address the particular issues.

Our mechanic back home said that he would estimate a 4 hour job adjusting the bands for the reverse gear - but also admitted he would really need to by looking at the transmission with the pan off.

Any help would be really appreciated as we are bringing our RV to a shop in the morning and are fearing being ripped off - and as musicians - funds are comically low.

Anyone have any suggestions to a good mechanic / shop in the Los Angeles area that would not require us to travel up any crazy hills?

Thank you!
Tyler

If you feel you could lend a direct hand or advice - please call or text me at Eight 6 2 - Four 3 2 - Zero 7 4 2

Tyler,
Go to Sales + Service Locator and enter Los Angeles, CA as your location. This will show you the Allison dealers and distributors in the area and there are bunches of them in the LA area. Take it there for service. That's your best bet. They will be able to sort it out. Could be you've lost the low clutch which is used in 1st and Reverse. The AT545 does not have band clutches. Also, have them draw an oil sample to see what the fluid shows before the fluid is drained. I'd like to see the results of the oil sample (Note: I was the Transmission Fluids Engineer at Allison from 1990-2009 when I retired). You can get a test kit at JG Lubricant Services, LLC. I recommend the Advanced Oil Analysis Kit (JGOA22). You can use the Discount Coupon Code "Forum Buddy" to get a discount on the test kit.

Do not use SAE 15W-40 Engine Oil or any DEXRON-III or any DEXRON-VI in the transmission. They will continue to give you problems. Use either Shell SPIRAX S6 A295 Synthetic ATF or BP/Castrol TranSynd. TranSynd will be available at the Allison dealer and have the Allison dealer or distributor replace all the fluid in the transmission and cooling circuit with the BP/Castrol TranSynd or Shell product.

NOTE TO FORUM "WATCHDOGS": MY INTENTION IS NOT TO ADVERTISE HERE. I'M SUGGESTING THE CORRECT ACTION PLAN WHICH INCLUDES A GOOD ANALYSIS OF THE USED FLUID.

dbarton291 · 01-12-2015, 05:29 AM

That sounds pretty major. A remanufactured transmission may be in your future.
There are no bands to adjust in an Allison on-highway transmission. It's all clutches.
The AT-545 uses first and fourth clutches for reverse. Forward and first for first gear. If you can't back up, but you can go forward, it sounds like fourth clutch may be burnt.
Make sure the shift linkage is properly adjusted after the repair.

Quote:

Originally Posted by omingnome

An unfortunate update :

The past few days the transmission has been extra strange - slipping harder in first and yesterday we lost reverse. - which led to a $125 tow to be pulled 5 feet backwards so we could go forwards.

Looks like we are taking it to a shop - unfortunately we are far from home in Savannah, GA where we have a great, trustworthy mechanic - we are currently in Los Angeles, CA -

Does this sound like the transmission and torque converter are going to need to be completely replaced or does this sound like we could find someone to address the particular issues.

Our mechanic back home said that he would estimate a 4 hour job adjusting the bands for the reverse gear - but also admitted he would really need to by looking at the transmission with the pan off.

Any help would be really appreciated as we are bringing our RV to a shop in the morning and are fearing being ripped off - and as musicians - funds are comically low.

Anyone have any suggestions to a good mechanic / shop in the Los Angeles area that would not require us to travel up any crazy hills?

Thank you!
Tyler

If you feel you could lend a direct hand or advice - please call or text me at Eight 6 2 - Four 3 2 - Zero 7 4 2