quickfarms
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What is the history of this truck. Did you get it from gl or a private party? What service has been done to it?
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Allison Transmission issue
- Thread starter ARYankee
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ARYankee
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It's a GL truck. It probably needs the fuel filter replaced. I will be doing that after this much needed rain passes through. I haven't gotten around to changing all the filters yet so I guess that's a good place to start.
Danl
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Danl M915A1
I'm goind to be sitting in on this because I'm haveing things go wrong also. I'm changing all my filters this weekend. My truck smoked from day one I drove is 1500 miles home and it smoked. I put the dump body on it and really started to work it with heavy loads. the truck dose not smoke black any more. is this good ? and the power has droped off greatly it shift out of frist as soon as the truck start rolling and 2nd jest sit there and luggs than it feels like something kick in and she start to go, Im hoping that it fuel catching up after frist gear burnt all that was in the filter.
I'm goind to be sitting in on this because I'm haveing things go wrong also. I'm changing all my filters this weekend. My truck smoked from day one I drove is 1500 miles home and it smoked. I put the dump body on it and really started to work it with heavy loads. the truck dose not smoke black any more. is this good ? and the power has droped off greatly it shift out of frist as soon as the truck start rolling and 2nd jest sit there and luggs than it feels like something kick in and she start to go, Im hoping that it fuel catching up after frist gear burnt all that was in the filter.
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Mike, if your truck does not downshift when you are driving up a hill, something is wrong. All of my trucks downshift just like you might expect when losing speed headed up a hill. I have never had to manually downshift my trucks. I put it in 1-5 and head out...unless I am doing something off road where I want to control the speed and power of the truck.Man, 45 MPH on an incline? I wish mine did that. I find that these allisons don't really like to downshift on their own up hill. Or at least I don't like how low the RPM's get on inclines. I typically downshift to keep my speed up.
The governor is RPM dependant. Most are set around 2100 or so. Question about the transmission and shifting? Check out this video
[media]http://www.youtube.com/watch?v=leCEmJA0WsI[/media]
wsucougarx
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Bruce, she'll downshift on her own but I don't like when. Probably need to have the shift points looked at.
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Hard for me to explain when my transmissions downshift. I have had trucks that seemed to downshift late or upshift early. As you pointed out, most of the time, those things dealt with the shift points being out of whack. I just never had to manually downshift my trucks. Anyway, good luck!
Danl
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Danl M915A1
Ok i changed my fuel filter, the smoke came back some what not as black but the motor is cleaner now because I have been running it hard, the power is better, the tranny must shift by Rpms or maybe power but all seems better I will know more in time because she is going back to work I did run the fuel tank real low two times and I think the low fuel plug the filter. in the filter i found some red RTVand a pease of wood chip the filter was a mess Hopefully the tank is clean now . So try fixing your fuel filter frist 27 bucks done Thanks you SS member for the filter Clue
Ok i changed my fuel filter, the smoke came back some what not as black but the motor is cleaner now because I have been running it hard, the power is better, the tranny must shift by Rpms or maybe power but all seems better I will know more in time because she is going back to work I did run the fuel tank real low two times and I think the low fuel plug the filter. in the filter i found some red RTVand a pease of wood chip the filter was a mess Hopefully the tank is clean now . So try fixing your fuel filter frist 27 bucks done Thanks you SS member for the filter Clue
Danl
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Danl M915A1
Try your fuel filter the rpms will chang and I'm sure shifting will come around with the rpms were they are supose to be . its the cheapes test 27 bucks 10 mim
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Of the 7 or 8 939 series trucks I have driven, they all downshift on their own with a big BANG! Except for one which is an M923a2 with an 8.3 Cummins. It shifts like a dream. The others all shift like they are trying intentionally to scare you.
I have gotten into the habit of manually downshifting at just below 1500 RPM. I back off the throttle a bit and drop it down and it goes nice and smooth. If you let the Allison decide when to do it, well that can be a bit unsettling.
I have had the fluids changed and the shift points set by the regional Allison shop and it is still not very pretty when it comes to downshifting.
Danl
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Danl M915A1
I was able to fix alot with the filter. running the truck real low on fuel, fould it up . Hopefully the fuel tank is clean now LOL. The tranny shift points. um. when the truck is empty, all is good. with 20 or so ton, or say loaded, . the roads I haul are small hills and curves . the speed limit is 40 to 45 and lots 30 35. 5ft gear is useless. if I let the truck sift into 5ft,she will lug and slow down to unsat speed than down sift when I get mad and stomp on the fuel. Here is what I do. from a stop I start in 1-2 and I shift up the gears my self, keeping the 400 in its power band, when I hit a pease of road that is flat . I than slid it in 5th. 5ft is only a overdrive, at the end of the flat road And I slow for a curve I pull the curve and down sift back to fourth. what I'm doing is driveing this thing as if it was a Hydro Mattic. and every thing is real good. this old school auto tranny in my thoughts is nothing but a new genneration hygro matic. Alot of inproving has been done to the auto mattic in 20 or so years new truck shift better now. But the old 754 crd allie is better built and last longer before rebuilt is needed , but it is what it is. New Generration Hygro Mattic
I was able to fix alot with the filter. running the truck real low on fuel, fould it up . Hopefully the fuel tank is clean now LOL. The tranny shift points. um. when the truck is empty, all is good. with 20 or so ton, or say loaded, . the roads I haul are small hills and curves . the speed limit is 40 to 45 and lots 30 35. 5ft gear is useless. if I let the truck sift into 5ft,she will lug and slow down to unsat speed than down sift when I get mad and stomp on the fuel. Here is what I do. from a stop I start in 1-2 and I shift up the gears my self, keeping the 400 in its power band, when I hit a pease of road that is flat . I than slid it in 5th. 5ft is only a overdrive, at the end of the flat road And I slow for a curve I pull the curve and down sift back to fourth. what I'm doing is driveing this thing as if it was a Hydro Mattic. and every thing is real good. this old school auto tranny in my thoughts is nothing but a new genneration hygro matic. Alot of inproving has been done to the auto mattic in 20 or so years new truck shift better now. But the old 754 crd allie is better built and last longer before rebuilt is needed , but it is what it is. New Generration Hygro Mattic
quickfarms
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Danl what truck do you have that has a 400 in it?
Danl
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Danl
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Danl M915A1
there is no onboard computer in these old truck. no sencer nothing to tell the tranny what to do, jest oil flow and presser, when the truck is loaded heavy you have to tell the tranny what to do. you as the driver has to do what ever it takes to keep the deisel in its power band the 400 cummins is 2200, I think the 250 is also 2200 run the speed limit of 40 mph with the truck loaded, and the tack sitting at 2000 and you will be in fourt gear, and plenty of power a small hill bougs you down under 2000, don't let off of the fuel jest slid it in 3rd 2150rpm and you creast the hill at about 38 miles per hour. do nothing and you will lug you motor and crawl up the hill and think the truck is sack less. Be a truck driver shift tha tranny drive the truck never lug a deisal, or you will pay the price of rebuilding it. Cummins love to wine at 2100. so wine it
there is no onboard computer in these old truck. no sencer nothing to tell the tranny what to do, jest oil flow and presser, when the truck is loaded heavy you have to tell the tranny what to do. you as the driver has to do what ever it takes to keep the deisel in its power band the 400 cummins is 2200, I think the 250 is also 2200 run the speed limit of 40 mph with the truck loaded, and the tack sitting at 2000 and you will be in fourt gear, and plenty of power a small hill bougs you down under 2000, don't let off of the fuel jest slid it in 3rd 2150rpm and you creast the hill at about 38 miles per hour. do nothing and you will lug you motor and crawl up the hill and think the truck is sack less. Be a truck driver shift tha tranny drive the truck never lug a deisal, or you will pay the price of rebuilding it. Cummins love to wine at 2100. so wine it
ARYankee
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Well I want to thank everyone for their input and help. I know more about my transmission now. I have narrowed it down to it being a fuel issue from post advise and after driving it this past weekend. I plan on changing my filter and depending on how it looks I will go from there.
ARYankee
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Turned out to be my fuel line from the filter to the IP was kinked really bad. I got a replacement from NAPA and took it for a good test drive this weekend and all is well.