Allison Transmission Questions

That is definitely possible. Any foam or bubbles on the dipstick?

dbywaters;78199 said:
I drive 22 miles from home to a nearby campground Friday. Transmission shifted perfectly, and for the first time up-shifted under full throttle to 4th on a grade steep enough to require a 4-3 downshift. I believe my problem is related to the amount of ATF in the transmisison. I checked the hot fluid level after returning home yesterday and it appears I was at the lower portion of the hot range. I still plan on completing the stall test and pressure checks as soon as I can. I sure hate the extreemly long fill tube and dip-stick...

Power is a non issue with my engine, I've towed and camped since 88 and this coach is down right quick compared to others I have driven.
 
The dipstick may not be calibrated properly for that transmission. You can check the dipstick calibration with a procedure in the MT Mechanics Tips booklet. I've posted a link to that book on here before.

dbarton291;78204 said:
That is definitely possible. Any foam or bubbles on the dipstick?
 
No foam on the dipstick. It take about 5 tries to finally see the level since the fluid is so clear. It might be that my coolant lines and cooler capacity keeps an air bubble until run up to temperature. I'm going to add another quart before next trip.




dbarton291;78204 said:
That is definitely possible. Any foam or bubbles on the dipstick?
 
Sorry it has taken me this long to get on here. The flare occurs at part or full throttle, loaded and unloaded. The flare is intermittant, not connected with towing.
Should I be checking harness plugs (unplug, replug), etc. Filters are recent, fluid is clean no burnt smell. Thanks for your help.
 
about how many engine RPM is the flare?

JackG;78397 said:
Sorry it has taken me this long to get on here. The flare occurs at part or full throttle, loaded and unloaded. The flare is intermittant, not connected with towing.
Should I be checking harness plugs (unplug, replug), etc. Filters are recent, fluid is clean no burnt smell. Thanks for your help.
 
dbywaters;78213 said:
No foam on the dipstick. It take about 5 tries to finally see the level since the fluid is so clear. It might be that my coolant lines and cooler capacity keeps an air bubble until run up to temperature. I'm going to add another quart before next trip.
I have the MT service liturature, and the overhaul manual for 600 series transmissions. I calibrated the dipstick using a clear mason jar, I disconnected the dipstick tube from the pan and held it away from the pan far enough to slip a the glass jar filled with transmission fluid up over the tube to the height specified in the service manual as "cold full". At the same time I had my son pull the dipstick and check it multiple times to verify the level coorisponded on the stick. We adjusted the stick until it did. I then re-attached the tube to the pan and filled it with fresh ATF.

Since my last note, I have taken a couple trips with additional fluid, my hot level is now correct. I noticed the 3-4 shift was much improved but still not as clean as the other shifts. I have always noticed I had smoth 3-4 shifts after removing and replacing the governor, this led me to think I might have a governor problem so I ordered a new governor from sonnex and replaced it this week. I compaired my old governor against the new one, found the first section of the govenor shaft adjacent to the gear was worn 1- 1/1000's of an inch more than the rest of the shaft. I also noticed the leading edge of the spool valve was worn.. actually rough in appearance. The remainder of the governor looked ok. I drove the coach with the new governor and noticed all shifts occured at higher RPM's, as if I had adjusted the modulator cable (but I hadn't) My 3-4 shift has definitely improved, and I could not reproduce a shift problem. I did not drive a long distance, probably less than 10 miles so I cannot say that I definitely have a better shifting transmisison yet. I will be driving 300 miles next weekend so I will report my findings then.

thanks so much for the replys and suggestions. I hate to shot-gun troubleshoot, but the governor was only 60 bucks and takes about 10 minutes to replace.... so I took a chance replacing this unlikely part.

Doug
 
dbywaters;78498 said:
I have the MT service liturature, and the overhaul manual for 600 series transmissions. I calibrated the dipstick using a clear mason jar, I disconnected the dipstick tube from the pan and held it away from the pan far enough to slip a the glass jar filled with transmission fluid up over the tube to the height specified in the service manual as "cold full". At the same time I had my son pull the dipstick and check it multiple times to verify the level coorisponded on the stick. We adjusted the stick until it did. I then re-attached the tube to the pan and filled it with fresh ATF.

Since my last note, I have taken a couple trips with additional fluid, my hot level is now correct. I noticed the 3-4 shift was much improved but still not as clean as the other shifts. I have always noticed I had smoth 3-4 shifts after removing and replacing the governor, this led me to think I might have a governor problem so I ordered a new governor from sonnex and replaced it this week. I compaired my old governor against the new one, found the first section of the govenor shaft adjacent to the gear was worn 1- 1/1000's of an inch more than the rest of the shaft. I also noticed the leading edge of the spool valve was worn.. actually rough in appearance. The remainder of the governor looked ok. I drove the coach with the new governor and noticed all shifts occured at higher RPM's, as if I had adjusted the modulator cable (but I hadn't) My 3-4 shift has definitely improved, and I could not reproduce a shift problem. I did not drive a long distance, probably less than 10 miles so I cannot say that I definitely have a better shifting transmisison yet. I will be driving 300 miles next weekend so I will report my findings then.

thanks so much for the replys and suggestions. I hate to shot-gun troubleshoot, but the governor was only 60 bucks and takes about 10 minutes to replace.... so I took a chance replacing this unlikely part.

Doug
A worn governor usually causes unusually high upshifts. I don't know about the aftermarket Sonnax governors, but I know the Allison governors are marked on the top 460, 461, 462, etc. to match them with the valve body calibration, and they're different part numbers. If the RPM of all your upshifts increased, the new governor is different from your old one. That's not necessarily a bad thing, especially if the 3-4 shift improved. Raising the shift point almost always improves shift quality, because if you get up close enough to max governed speed, or in the droop, the engine is starting to pull itself out of fuel. Less power, less bang as the oncoming clutch engages.

I've never heard of using a glass jar to calibrate a dipstick. If it works, that's great. I've attached a wire to the dipstick tube and marked it, then compared it to the dipstick. I've also made a tool by drilling out a drain plug and attaching clear tubing to a fitting in the drain plug and held that up next to the transmission and measured. On the WTs, the dimensions are published so you can measure the tube and dipstick, do a little arithmetic and calibrate.
 
The sonnex gear is also a 461, same as the one removed and identical in appearance. Glass jar was simple and required no math :) before I removed the tube from the pan I marked the correct fluid level on the tube with electrical tape, then removed the tube from the pan, filled a mason jar with atf and held the jar over the tube with fluid level to the electrical tape. Then had my son check the dipstick over and over again, adjusting the length of the stick to calibrate. I just could not think of anything simpler than that and I did not have to waste any AFT in the process...I had thought about drilling an tapping a drain plug..
BTW, my shifts are within a 100 rpm of prior shift points, the big test is the weekend.

Thanks for all your advice.


dbarton291;78510 said:
A worn governor usually causes unusually high upshifts. I don't know about the aftermarket Sonnax governors, but I know the Allison governors are marked on the top 460, 461, 462, etc. to match them with the valve body calibration, and they're different part numbers. If the RPM of all your upshifts increased, the new governor is different from your old one. That's not necessarily a bad thing, especially if the 3-4 shift improved. Raising the shift point almost always improves shift quality, because if you get up close enough to max governed speed, or in the droop, the engine is starting to pull itself out of fuel. Less power, less bang as the oncoming clutch engages.

I've never heard of using a glass jar to calibrate a dipstick. If it works, that's great. I've attached a wire to the dipstick tube and marked it, then compared it to the dipstick. I've also made a tool by drilling out a drain plug and attaching clear tubing to a fitting in the drain plug and held that up next to the transmission and measured. On the WTs, the dimensions are published so you can measure the tube and dipstick, do a little arithmetic and calibrate.
 
Sounds like the 2500 has the downshift preselect wired to the brake and is on all the time. The 3500 doesn't. Doesn't sound like a problem to me, unless there's times you want to coast down a hill in the 2500.


johnybarkerr;78587 said:
I have a 3500 Chevy 4x4 with a duramax and of course the allison tranny. I also have a 2500 with the 8100 Vartec and the allison. The 2500 will really slow you down if you just tap the brake. The tranny cuts in and you'd have to add fuel going down hill to keep going. The 3500 with the duramax doesn't seem to work that way. Do I have a problem?
 

DBLB

Junior Member
I have a 1999 Fleetwood discovery. The odometer is reading about 1.3 miles for every mile I travel. I had the sensor at the tranny cleaned. Unfortunately that did not solve the problem. Speedometer is working correctly. Any ideas?
 

LL1956

Junior Member
DBLB;81420 said:
I have a 1999 Fleetwood discovery. The odometer is reading about 1.3 miles for every mile I travel. I had the sensor at the tranny cleaned. Unfortunately that did not solve the problem. Speedometer is working correctly. Any ideas?
What size of tire do you have? 235/80 was the OEM size. If you have a smaller diameter size on. It will cause the reading to be higher.
Any Cummings shop can reprogram the EMC for how many RPM your tires turn.

With that said the Speedometer should be off the same as well. When traveling at 60 MPH it should read maybe 63 MPH
 
DBLB;81420 said:
I have a 1999 Fleetwood discovery. The odometer is reading about 1.3 miles for every mile I travel. I had the sensor at the tranny cleaned. Unfortunately that did not solve the problem. Speedometer is working correctly. Any ideas?
Do you know when this started? Has it always done it since new, did it start recently, did it start after any transmission or other service work?

Is the speedo also 30% fast? The tire size is also a good question.
 

DBLB

Junior Member
dbarton291;81493 said:
Do you know when this started? Has it always done it since new, did it start recently, did it start after any transmission or other service work?

Is the speedo also 30% fast? The tire size is also a good question.
Tires are orignal OEM size, Speedometer is working correctly. I have checked several times with GPS.
 
DBLB;81528 said:
Tires are orignal OEM size, Speedometer is working correctly. I have checked several times with GPS.
If the speedo is correct, there's no problem with the signal from the transmission. Sounds to me like the speedo head itself has a problem.
 
Hi--I have a MT654 Allison trans in my 1986 military truck --has a cummins ntc250 diesel--this trans has 10w motor oil in it--military standard------I have a very pounding downshift 2nd to 1st--the drivetrain jumps like I hit a hole in the road----is there any adjustment for this--thanks---I use this as my RV
 

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I am the new owner of a 06 Chevy Duramax with Allison 1000 trans. Owners manual states if high trans temp noted when towing to pull over and place in N (nuetral), set brake, and high idle until temps come down. Also noted when outside temp F below 32 high idle enable warms up trans fluid. Does fluid pump to cooler/heater work more effectively in N? and If so why not place in N for more effective warm up on cold temp mornings? Does the trans fluid pump move more or less fluid through the cooler(heater) in N than park or are there check valves that prevent some fluid transfer in P?
 
Hi, Hoping you may know any common problems that may help with our MTB647. The transmission is dropping into neutral every time it downshifts from 2nd to 1st. Originally it was only when the transmission warmed up, now it every time. When coming to a stop or near stop (anytime it wants to drop into first) there is no response from 1st gear. At idle it takes 5-10 seconds to re-engage, if you raise the revs, it engages quicker. It appears to be the 1st Clutch, because if you try engaging Reverse, it has the exact same delay. Please note, there is no slippage as such, you can hear the whir as the box stops spinning and the mild clunk at is locks in. Immediately after the clunk you can put your foot to the floor and it will pull like a train. Please note, that this only happens on the downshift. When you shift from neutral to either Forward or Reverse it immediately firmly engages (except when it has just downshifted, in which case it doesn't matter what you do). We are a repairer, but we do not want to start dismantling the transmission until we have exhausted all the easy problems. Here is some of items we have checked and noted:
1. Changed Pan Filter & Fluid
2. Main Pressure at idle 450kpa
3. Modulator appears correct when compared to similar bus. It has a Cummins L10 250hp, and the Modulator uses a slide connection which does not actually come in play until heavy throttle is applied.
4. Checked shift selector position for correct alignment.

Other items we have noticed that may not necessarily be associated:
1. Slight flaring/clunk when upshifting from 1st to 2nd under heavy acceleration.
2. Reverse judders but doesn't appear to be actually slipping, more like rapidly engaging and disengaging. (Does not happen in any other gear at all)

If I had to guess, I would have said it seems like the 1st Clutch Valve is sticking, but then it doesn't do it when engaging from neutral.

Your thoughts appreciated.

Kind Regards, Jason
 
In neutral or park, the fluid moving from the trans to the cooler is the same. The only difference between neutral and park, is in park, the parking pawl is locking the output. If you want to warm it up a little quicker, put the trans in gear and go to high idle for a little while. Once the trans is in gear and the vehicle is stopped, the turbine side of the torque converter is stopped because it's now connected to the output. Give it a little RPM and you've got friction between the fluid and the turbine which creates heat. Just be careful. Don't do it too long. Watch the temp.

DB

mcnairt;82324 said:
I am the new owner of a 06 Chevy Duramax with Allison 1000 trans. Owners manual states if high trans temp noted when towing to pull over and place in N (nuetral), set brake, and high idle until temps come down. Also noted when outside temp F below 32 high idle enable warms up trans fluid. Does fluid pump to cooler/heater work more effectively in N? and If so why not place in N for more effective warm up on cold temp mornings? Does the trans fluid pump move more or less fluid through the cooler(heater) in N than park or are there check valves that prevent some fluid transfer in P?
 
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