Anyone with a six speed behind a 5.9 Cummins or with experience of this transmission care to comment on the following behavior? At about 60mph trans is in 5th gear engine at 1800 rpm, if you remove pressure on gas pedal trans downshifts to 4th, if you keep steady pressure on gas pedal it will remain in 5th. Have been told this is set up this way to give engine braking assistance but it seems a little troublesome to me. I have always thought that brake pads were cheaper than engines but I just don't know about this. Transmission only shifts into 6th at 75 mph. Does all this sound like typical behavior or is it a matter of adjustments, tweaking or repair work?

quote:

Originally posted by izomage:
Anyone with... experience... care to comment on the following behavior?

Does all this sound like typical behavior or is it a matter of adjustments, tweaking or repair work?

What year coach do you have? What HP range is your diesel? Would you happen to know what rear end ratio you are running?

I believe your transmission can be adjusted with little trouble from a dealership that works on the Allison Automatics. They would just plug in their proprietary ECM diagnostic scanner/reprogrammer and readjust your shift range and or converter lockup points.

I know this sounds basic, and I'm sure you checked, but fluid level, fluid condition, fluid type and filter changes all affect the psi going to the transmission valves and clutches. Too much or too little fluid will make a big difference.

--Checking the fluid level on an Allison--

Equipment on level surface

Transmission fluid hot

Engine at an idle

Transmission in neutral

All of these conditions must be met before checking the fluid level. Too cold, wrong angle, in gear or engine at a higher rpm and you'll have a wrong reading.

A world of knowledge awaits behind this link. I could have supplied a link to your transmission if you posted the transmission model. If you don't know it, you'll find that info too in the above link.

While I might be a diesel mechanic, most over the road trucks do not have an Allison. I could wet the bottom of a thimble with knowing the model based on year and speeds of a transmission.

Anyone with a 5 speed that would like a 6 speed in their coach? There are kits available for certain transmissions to change this. The price is only $ 2,300.00 and at today fuel prices could pay for itself in only a few short years Besides, it a goodie for your toy and money means nothing, right?

Might I suggest, to all, that you add a signature profile? Include the year, model, engine HP rating, engine size and transmission model etc. It will make it easier for us to know the vitals of your coach and if someone has the same setup as you, it will be easier to ask questions of that member.

If anyone needs a hand setting that up just email or PM me and I'll do it for you.

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	1990 Barth Regis Widebody 8908 0128 40RDS-C1 L-10 Cummins Allison MT647 Transmission Spartan Chassis		1991 Medical Lab Conversion 9102 3709 33S-12 Ford 460 MPFI C6 Transmission Oshkosh Chassis
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I have a 5.9 followed by the 6 speed, I go into and stay in 6th at about 56 MPH unless I have it flat on the floor and then it will go to 75 or so before it will go to 6th. I can kick it into 5th by flooring it. Mine will not shift back to 4th if I lift until about 50 or so.

This sounds like the throttle position sensor is out of adjustment and can be set by any good Allison shop.

I have 19.5 tires and a 4.10 rear end, if you have 22.5 tires and a similar ratio diff, your shift points will be at a higher MPH then mine but your estimate of 1800 at 60 sounds similar to mine. I run about 1925 at 70 MPH in 6th.

I have a problem with my throttle position sensor awhile back, when every I lifted, the "check trans" would light, turns out that the linkage from the throttle plate was worn and allowed the throttle position sensor to go out of cal, I took it to an Allison shop that diagnosed the problem but wanted four to five hours to rebuild the linkage, I declined and drove home, they said it would not damage the transmission, Replaced a couple of washers that were worn and the light went off and didn't return. I should go back to an Allison shop now to have the linkage reset so that the proper "count" is shown at idle but just haven't gotten around to it!

Concerning oil changes in the Allison, I have done a lot of research and found that it is really important to change the oil/filters on a regular basis (30K-50K miles is regular ATF is used) and more importantly, use synthetic!!!! When Allison switched over to a synthetic oil, their warranty work dropped by 70% and the estimated trans life time was extended by 100%! My trans oil had never been changed in 70K miles---not good--- so I have changed to synthetic at 75K and then another drain/refill at 90K, I have one more to do at 100K then I will consider that I have most of the old oil diluted and out.

After I change at 100K I don't plan another change until 175K, with synthetic, you can extend the change interval to 75K+ miles.

I have an Allison MD3060

Much thanks for the help guys. I am trying to evaluate a 1992 Spartan chassis 33ft Breakaway, over the telephone at this point. The transmission is almost certainly the same MD3060 as MWrench's 30, although the shifting characteristics may be a little different due to the heavier bus I suppose. I got this information from the owner, who has been driving it this way for some time, apparently. He was told by an Allison shop (I presume, and hope) that the trans may have been set up that way and he may adjust to it and learn to like its behavior. On the face of it I am sceptical and with Ed's description of his shifting pattern I am becoming convinced that the transmission is not adjusted properly, or worse. The fact that it doesn't use 6 th until after 75mph, and on a longer coach' just doesn't make sense to me. I didn't know the 5.9 would push these Breakaways at 80mph for sustained cruising. I would think all Breakaways would have the same 19.5 wheels but perhaps the 33 uses the 22.5 size. In any event I know a lot more now than a little while ago but still can use any other scraps of wisdom that may be available. The Allison control module has diagnostics and error code history available ( if it hasn't been wiped ) so if I go inspect this Barth I can check for them. Just to think out loud here, it seems that I need to check on the tire size and also seriously consider having an Allison tech check this out before making any final decision.

quote:

Originally posted by izomage:
I would think all Breakaways would have the same 19.5 wheels but perhaps the 33 uses the 22.5 size.

Some later Breakaways had 22.5s, even 30-footers.

Just took a long hard look at the photo of this 33 and I am quite sure those must be 22.5 wheels. Still, if you relax the pedal at 60 /65 mph I don't think it should immediately downshift to 5th. Throttle position sensor as Ed suggested, or maybe flakey TCM or ECM ( groan !).

"...it is really important to change the oil/filters on a regular basis (30K-50K miles is regular... "
IMHO: (emphasis on humble)
I, too, have a 3060 (but an 8.3 Cummins). The filters are not nearly as important as the actual fluid change. I change fluid yearly, but I use Dexron-III (non-synthetic): 16 quarts, if memory serves, and that's why I use "real oil" fluid rather than synthetic. The filter kit has two filters and is about $70 from Allison; I change filters every two years, since I only drive about 5,000-6,000 miles annually - long highway (extended freeway) cruising; the (two) filters are metal mesh and as with autos, don't normally lose effectiveness until 25,000 or more miles. Months of mostly sitting is bad on the fluid, moreso than mileage. Even with synthetic, I wouldn't want to change less often than 24 months. 25K miles would equate to a 4- or 5-year interval - much too long for a fluid change.
PS: My owner's manual recommends annual fluid change if mileage is low. And, yes, Allison does recommend synthetic fluid especially for constant-use vehicles.
"I have most of the old oil diluted and out."
After I change filters and fluid, the new fluid is absolutely clear. My understanding is that the MD3060 is designed such that no fluid remains in the transmission as is the case with, e.g. a turbo 400. Am I wrong on this?

quote:

Originally posted by Gunner:
My understanding is that the MD3060 is designed such that no fluid remains in the transmission as is the case with, e.g. a turbo 400. Am I wrong on this?

The Turbo 400 can drain its case and pan completely. But a fair amount of fluid stays in the torque converter, as it does not have a drain plug. I had an Allison converter on one TH400, and it did not have a drain plug, either. I don't know how a trans can be completely gravity drained of fluid without a converter drain plug. I let the trans pump it until it runs clean.

"I don't know how a trans can be completely gravity drained of fluid without a converter drain plug."

The MD3060 has three separate places to drain fluid: pan, via traditional plug; and each of two filter compartments which dump about 1-1/2 quarts (each) when a bottom plate -through which the filter is inserted into a chamber- is removed. I wondered if the converter drains into one or both of the filter chambers, thereby completely emptying the unit of fluid. ???
BTW: This summer I drove 6,000 mostly interstate miles in six months after a fluid change in April; today the fluid is still so clean/clear it is difficult to read on the stick.

Actually, transmission fluid has a life of several years, unless overheated or contaminated. The main reason the change it is to remove clutch wear fines, and with many transmissions, to get at the filter, the pan has to be removed, so the fluid is changed. But changing it more frequently can't hurt...

Sitting doesn't really bother transmission fluid, the opposite of motor oil.

But I run synthetic in my 4L80E even with the Mag HyTec pan which increases capacity by a couple of quarts, and tranny temp, even on long grades in 100F weather never exceeds 205F. I plan on three-year change intervals (about 40K miles).

Synthetic oil is still cheaper than metal.

Someday, in the not to distant future, I hope to put all this useful transmission oil change information to good use. Before that day arrives I need a transmission worthy of synthetic oil. In my reading of the Allison 3060 operating manual it appears that this transmission can be programmed to do just about anything you want ( give me sixteen miles per gallon please ) so I am sure it can be made to operate in a more normal manner. What disturbs me is why the owner didn't just have have it done. There is only one reason I can think of that makes much sense, and it means there is more involved here than just programming.

I wouldn't put too much stock in the prior owner's oversight. Many folks' interest in things mechanical are limited to where to stick the ignition key, and how to start the engine. Others may think that any adjustments to a transmission will cost at least $2,000.

And it's never to late to switch to synthetic transmission fluid.

I think the transmission is ok after all. It's curious how the thought of spending money can make you a little hyper. This bus cruises in 5th at 1800 rpm doing 65 mph, shifts into 6th at 75 mph with rpm at 1800. Must be the same trans-axle set up as the 30 footers and the 22.5 tires account for the difference. I suppose with accurate tire diameters this can be calculated but I will save that one for a cold winter day when I need something to do to keep me awake.

What you notice calculates out almost exactly, using the tire diameters given by the manufacturers, not taking into effect of the "rolling radius". Hope the columns and rows will line up after I post this!

This also shows why I elected to go with 225R7019.5 on the front and stay with 8R19.5 on the rear, I didn't want to give up the 80 or so RPM at 70 that would have happened with the smaller 225 tires, The aluminum wheels I have are on 6 inch and the 245R tires that I would have like to use requires at least a 7 inch and preferable 7.75 inch wide wheel. 7 and 7.75 inch wheels are not made in the 19.5 X 6 bolt Budd as far as I could tell.

Tire size Diameter Circ Revs/mile 4th 5th 6th

8R19.5 33.3 104.61 605.65 2483 1862 1614
65 2690 2018 1749
70 2897 2173 1883
75 3104 2328 2018

225R70 19.5 32 100.53 630.25 2584 1938 1680
65 2799 2100 1820
70 3015 2261 1960
75 3230 2423 2100

245R70 19.5 33 103.67 611.16 2506 1879 1629
65 2715 2036 1764
70 2923 2193 1900
75 3132 2349 2036

245R75 22.5 37 116.24 545.08 2235 1676 1453
65 2421 1816 1574
70 2607 1955 1695
75 2794 2095 1816

Well they didn't so I will take the Excel sheet and put it up on my website later, I think you can make out what is posted, there are speeds listed for 60, 65,70, and 75 MPH the 60 MPH speeds are on the same line as after the initial tire diameter spec.

HTH