ALLISON TRANS DOWN SHIFT CLUNK

[wildbuckaroo]

Hi there,

I just bought a 97 Beaver Marquis with a cat 7.2 and an Allison transmission. Now sometime when I am slowing down it seems to have harsh downshift clunk and I think that is a 5-4 clunk. Everything else seems ok, I wonder if there is a fix for it or can it be reflashed to correct this. Has anyone else had problems like this?

 

[dbarton291]

Re: ALLISON TRANS DOWN SHIFT CLUNK

Which Allison is it? MD3060? Do you have an exhaust or jacobs engine brake? Any trouble codes?

 

[Allison Expert]

Re: ALLISON TRANS DOWN SHIFT CLUNK

Resetting the transmission computer can help, but db is right in asking if it has a jake brake of exhaust brake of some sort. What about a Tellma system, or retarder?? And need to know if you have any trouble codes and if the oil level is ok....

 

[gouldam]

Re: ALLISON TRANS DOWN SHIFT CLUNK

I have a 2004 Winnebago Vectra with a 3000MH Allison with a 350 Cummins. I also have a rough shift from 5 to 4, But mine is under load (hill climbing).

Freightliner in Gaffney reset the computer. It did not change anything. There are no codes. I have a Jake Brake, but this is turned off except when I need it. Is this a normal Allison thing or should i have it looked after? I kind of forget the problem on the east coast where we spend most of the time. We seldom have a down shift past 5, however, when we travel out west we really notice it. Is this a normal quirk for this Allison or should I get it looked at? Would this be a big repair or a simple adjustment?

 

[dbarton291]

Re: ALLISON TRANS DOWN SHIFT CLUNK

gouldam - 7/17/2010 8:22 AM

I have a 2004 Winnebago Vectra with a 3000MH Allison with a 350 Cummins. I also have a rough shift from 5 to 4, But mine is under load (hill climbing).

Freightliner in Gaffney reset the computer. It did not change anything. There are no codes. I have a Jake Brake, but this is turned off except when I need it. Is this a normal Allison thing or should i have it looked after? I kind of forget the problem on the east coast where we spend most of the time. We seldom have a down shift past 5, however, when we travel out west we really notice it. Is this a normal quirk for this Allison or should I get it looked at? Would this be a big repair or a simple adjustment?

It's really hard to say from your description if this is a problem or not. Most of the shifts in a 3000MH you can just barely feel. If you feel one, it's usually not a problem.

If however, the shift makes a loud bang, or interrupts power to the ground while you're climbing and then bangs into gear, or really rocks the vehicle around, you might want to get it checked.

Make sure you have genuine Allison filters in it, and good oil, preferably Transynd.

How many miles are on it?

 

[gouldam]

Re: ALLISON TRANS DOWN SHIFT CLUNK

The unit has 45K on it. It had 10k when I purchased it use 4 years ago. I had an M3 preventative maintenance preformed last fall at 40K at the Freightliner motor home chassis factory service center in Gaffney SC. All filters changed and new fluid. The invoice does not give the brand of filters and fluid. Nothing has changed since service, although I have not done much hill climbing since then.

The harsh downshift is not new. It's been with the unit since I have purchased it. Unfortunately I did not notice it during the test drive. I wouldn't say it is severe. It is just one short solid clunk, and only noticed under heavy load. It has not gotten worst.

 

[dbarton291]

Re: ALLISON TRANS DOWN SHIFT CLUNK

gouldam - 7/18/2010 7:15 PM

The unit has 45K on it. It had 10k when I purchased it use 4 years ago. I had an M3 preventative maintenance preformed last fall at 40K at the Freightliner motor home chassis factory service center in Gaffney SC. All filters changed and new fluid. The invoice does not give the brand of filters and fluid. Nothing has changed since service, although I have not done much hill climbing since then.

The harsh downshift is not new. It's been with the unit since I have purchased it. Unfortunately I did not notice it during the test drive. I wouldn't say it is severe. It is just one short solid clunk, and only noticed under heavy load. It has not gotten worst.

Based on your description, I'm not sure it would be worth the expense and hassle of trying to diagnose it. It doesn't sound like a failure in the making.

 

[04Pusher]

RE: ALLISON TRANS DOWN SHIFT CLUNK

Our 04 Meridian, feightliner with Cummins 300 and 3060 Allison has the SAME "Clunk". We bought it new. Had it checked out by Freightliner. They stated is was not a problem and not uncommon. Now have over 60K and all is well. Most of our driving IS in the Rockies.

Have fun!