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Allison transmission tips

BobWolf

Veteran Expediter
Owner/Operator
Offline
I've had several people call me regarding issues with Allison transmissions not going into gear. Especially with Hino trucks.

1) The most common causes are idle or engine RPM too high for safe engagement usually 950 to 1000 rpm is max safe engagement speed. This is to protect the transmission from "slamming" into gear and causing severe damage. So, if you put the trans into gear and nothing happens put it in neutral or park and check the manual engine idle, or maybe your foot may be on the throttle.

2) I found with 2014 and up Internationals so far if you don't push down on the brake pedal hard enough the transmission wont engage. Yes this happened to me in Watertown back in December when I had a friends truck for the week. My friend Garry who is a fellow driver and owner had to jokingly rattle my cage for about two weeks after I called him with what I thought was bad news.

3) ABS CODES. If you have an ABS light burning, or you have opted to ignore it for too long the ABS module will tell the transmission control module to get your attention by not allowing your torque converter to lock up. This affects your shift patterns, causes the transmission to run hot, as well as drivability issues.

4) Issues with air ride height. bags not properly inflated, sensor, etc., loose, damaged, dirty, worn connectors, damaged worn wire harnesses, plugged filters, are often culprits as well.

5) Engine performance issues, Low or excessive power output due to maintenance issues or performance mods like "power chips"

6) As Ive posted before, only Allison filters, and Synthetic fluid. Preferably Transynd, especially if under warrantee, or if an alternate fluid is used be sure it is Allison approved.

6) Lets not forget what I call garbage codes. The constant movement shaking, and weather conditions hot cold, damp, dry, etc. any occasional minor disruption of data to the module will trigger a code that gets stored at least temporarily. Now, there are no real issues it just happens. Too many occurrences to close together can raise hell with the TCM and shut down. A quick scan and clear resolves the issue and everything is all good. If the problem returns then you have to find out why.

The transmission, engine, brake, and body control sensors send useable data and faults back and forth some faults end up in the transmission control module for problems not originating with the transmission its self. If it goes long enough the transmission control moduel will at the very least put the transmission into limp mode only allowing limited function or completely shut the transmission down and it won't do anything at all. This is a way the transmission protects itself and doesn't self destruct.

Allison transmissions are pretty much bulletproof that's why they are the industry standard.
proper maintenance for the entire truck will provide several hundred thousand miles of service.

Be Safe.
Bob Wolf
 
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greasytshirt

Moderator
Staff member
Mechanic
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This pretty much hits the nail on the head.

Regular maintenance on the 2000 series Allison is so simple, it's ridiculous to ignore. The 3000 series is slightly more involved because it requires a ratchet and socket.
 

mugurpe

Seasoned Expediter
Offline
There are also harness/shifter-control problems that can happen which will prevent the truck from going into D. you can sometimes clear them by shifting to reverse before going to drive. So if you throw it in Drive and it doesn't shift into 1st, try going N->R->D in one fluid motion. Knowing this has saved my ass a couple times in different trucks and got the truck limped back to a mechanic.
 
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