M923 Transmission Assistance Please!

[Doomsday]

So, basically out of the blue, the transmission is not shifting into any of the forward gears. Truck had been running fine last weekend, went to go to pull it out to wash it up today and no go. Weird thing is, it goes into reverse just fine but then switching to 1-5 or any other gear set, it just acts like its still in neutral. Opened up the access door from cab and it makes a buzzing noise in neutral but then goes away when putting shifter into gear. Shut engine down and tried starting it in gear and no go, so thats normal. Put back in neutral and starts like normal. Fluid level is normal, nothing leaking, nothing looks out of place that I can see, transfer case is in gear, tried shifting it out of high to low and no change.......Very confusing how it just has sat for a week then suddenly it just doesn't work. Unfortunately I am not an auto trans guy, never owned an auto trans truck in my life, always been a manual trans owner and am still new to the 5 ton world. Please help with any gremlin advice!

Thanks guys!

 

[Doomsday]

Interesting how technical manual says if slippage occurs in all forward gears check fluid level but why would it go into reverse just fine and not any forward gears? Sorry, again, I am not very knowledgeable on autos.......

 

[Carlo]

The forward range and rear are seperate "bands". Its hard to see a auto trans loose front and rear at the same time. I would check first to see if the trans is really going into the forward gear. Block the wheels and apply the brake. You can do this with the motor off. A helper in the cab moving the lever would help so you can se how the trans is shifting.
How did the fulid smell?

 

[Doomsday]

Fluid smells fine and shifter is moving cable and lever on trans, just no go. This is just so weird how it was running fine a week ago. All I did was replace a headlight and a couple bulbs this week.

 

[BKubu]

Check the easy stuff first, but it could also mean that your transmission just went. I had a truck that was running and driving fine. Drove it one day and it would not go into reverse. Took it to Allison and they diagnosed it as needing a rebuild. So, I bit the bullet and did it. That was before so many parts trucks became available. I would find a take out if you determine that you need a transmission. But, as I said, try the easy stuff first.

 

[hank2424]

Auto trans 5 ton

New to forum. Does the tranny on a 5 ton have an electronic selonoid on it like the chevy 4x4's to shift transfer case?.... Just a quick thought..

 

[Doomsday]

Check the easy stuff first, but it could also mean that your transmission just went. I had a truck that was running and driving fine. Drove it one day and it would not go into reverse. Took it to Allison and they diagnosed it as needing a rebuild. So, I bit the bullet and did it. That was before so many parts trucks became available. I would find a take out if you determine that you need a transmission. But, as I said, try the easy stuff first.

Jeez, I hope your wrong, don't have the money for that.....plus I wouldn't know the first place to take it down here in Southern California. Only places I know that would work on the trans would be up in Central Valley/Fresno area where all the heavy farm trucks and equipment are. Gonna try a few more things then I guess I am pulling it out when I get a chance.

 

[juanprado]

I am not positive if these have them but check to see if there is a vacum modulator on the side of the transmission as I vaguely remember some gas engine w/ Allison using one but not sure on this one?

 

[Doomsday]

There is no vacuum modulator that I am aware of but I was examining the technical manual and wondering about the modulator since you had mentioned it. It is mechanical and wondering if it somehow came out of adjustment would that prevent it from selecting a forward gear? Like I mentioned above, the shift cable is moving the shift lever properly on the transmission to select a forward gear set but I guess I will maybe remove and re-adjust the modulator per the instructions in the technical manual.
Sucks though, I am busy with household things and family duties for rest of day and probably won't get to play with it more for 2 weeks as I will be out of town next weekend.....but please, any other ideas or advice, please chime in.

Thanks!

 

[M35A2-AZ]

Just look for a Allison dealer on the web.
Most big truck service company are Allison dealers.

 

[tamangel]

w/in 100 miles of Castaic

http://www.allisontransmission.com/locator/bing/locationlist.jsp?country=US&street=&city=castaic&state=ca&zip=&services=M&radius=100

Mike W

******

 

[BKubu]

I suppose it is possible that the shift modulator would prevent the transmission from shifting. In my past experience, problems with the shift modulator only affected when the transmission would shift (it shifted either early or late)...but I suppose it could be that the shift modulator gave out entirely.

 

[Doomsday]

Just look for a Allison dealer on the web.
Most big truck service company are Allison dealers.

That would be great if I could get the truck out of my driveway. I need to learn what could be wrong and not pay some outrageous amount of money to have something simple fixed.

It has to be something simple as it has always been driving fine. Going to pull pan and inspect selector shaft and possibly remove valve body to see if anything could be visibly wrong. If I can get it running, I may take it to my local Allison shop but the one I called in Sylmar quoted $210 just to inspect it.

 

[tamangel]

You are just off I5 and the Grape Vine, right?..seems like mobile mechanics would be a dime (relatively) a dozen around you.. A few calls should quote you something..

Good Luck..

Mike W

******

opps sorry, see that you already did that (calling)..

 

[M35A2-AZ]

That would be great if I could get the truck out of my driveway. I need to learn what could be wrong and not pay some outrageous amount of money to have something simple fixed.

It has to be something simple as it has always been driving fine. Going to pull pan and inspect selector shaft and possibly remove valve body to see if anything could be visibly wrong. If I can get it running, I may take it to my local Allison shop but the one I called in Sylmar quoted $210 just to inspect it.

I guess that would a problem, maybe someone close to you could give you a tow.

 

[Doomsday]

I guess that would a problem, maybe someone close to you could give you a tow.

Towing the truck is for sure not an option unless I can get my buddy to come down from upstate with his Dodge Cummins dually and using a tow strap to drag me down to a shop. I can't imagine what the bill would be with a big rig tow....

I have this Monday off and will be trying a few things and/or pulling the pan for inspection. I am guessing something has stuck in the valve body possibly or the shift selector lever is not actuating something inside. Either way I am determined to find out, learn and possibly fix. I build Honda IndyCar cylinder heads for a living down here in So Cal, so working on engines, transmissions, etc. is nothing new. I used to have a red '98 12v Cummins dually sled pulling truck that I built from the ground up and had the transmission in and out of that truck numerous times. Not a fun job, but it got easier the more times I did it.

Thanks for the help guys, any further ideas are always welcome. Trying to keep this fix on a budget as times are tough with finances.

Joe

 

[tamangel]

confirming again...no mobile mechanics in your area..? Might cost more for your buddy to come down (depending how far 'upstate' he is) than a relatively short big rig tow.. Call a tow place and get an estimate.. then at least you'll know what costs will/might be..

just my 2 cents.. big trucks=big bucks I guess...

Mike W

*******

 

[Doomsday]

confirming again...no mobile mechanics in your area..? Might cost more for your buddy to come down (depending how far 'upstate' he is) than a relatively short big rig tow.. Call a tow place and get an estimate.. then at least you'll know what costs will/might be..

just my 2 cents.. big trucks=big bucks I guess...

Mike W

*******

Yes, there are mobile services and I can't afford them. Big trucks = Big bucks, yes.....I knew this upon buying this truck, just gotta bite the bullet in cirumstances like this and be my own warranty station. It is a very warm n fuzzy feeling when you know you can fix such a problem like this on your own. Im just not an auto guy, always delt with manuals with single and double disk clutches. Those are a piece O cake.....this auto is a whole new animal for me.

 

[jw4x4]

Towing the truck is for sure not an option unless I can get my buddy to come down from upstate with his Dodge Cummins dually and using a tow strap to drag me down to a shop. I can't imagine what the bill would be with a big rig tow...



Joe

Towing a 5 ton with a dually and a strap is not a good idea. Tow bar it with another BIG truck.

 

[212sparky]

Around here a big tow is $130.00 an hour.