Lost Reverse on start-up !

[deerhunter7]

Had the trucked plugged in to warm engine , haven't driven for 2 weeks. Start up warm enough
that the glow plugs didn't come on , Truck starts Iwait for the voltage gauge to climb and it kind of jumped up. Put in reverse hit throttle and nothing but revs . Reverse indicator is blinking.
Put in drive and works back to reverse nothing, Shut truck off and restart put in reverse and goes right in. Everything seems normal now put check engine soon light stays on . Anybody know whats going on ??

[csimo]

I don't know if this is your problem or not, but the Allison suffers from torque converter leak down. If I let my D/A sit for over three days it must idle for a minute or so before reverse works.

Allison could easily fix this problem, which in my opinion is inexcusable for a modern automatic transmission. I'll bet the new Ford TorqShift won't have that problem.

[hickcox]

I suspect you should look at the Drivetrain forum topic labeled: Gear Indicator light

MudNurI is the person asking the question, the answer is probably the same.

[bryantch]

Unfortunately i too have experienced the same problem you had. apparently the allison is VERY sensitive to voltage. if the allison computer reads 8v or below during the start sequence it will not go into gear (f or r)! if you shut the truck off and turn it back on again it is supposed to then go into gear. i am not sure what the reason for this is but the the tech explained the whole thing to me the last 3 times i took it in for this issue (the problem with my truck was that it usually took 15-22 restarts to get the allison in gear).

additionally the prindle on the drivers side of the tranny has had problems. this also can cause the symptoms you describe (light on).

why gm decided to put a "feature" into the truck that would prevent a truck with a dead battery that had been jumpstarted to go into gear and let you get back on your way escapes me.

[ChevysRus]

The "procedure" to follow anytime your truck sits for a week or two is as follows and this is straight from Big AL

Start the truck and don't put it in gear, on start up after sitting sometimes a big slug of air will pass through the system sending all kinds of codes to the TCM. If you put the truck in gear the codes are locked in and the Ally will go into self defense mode (won't move in any gear).

If you shut the truck down before putting it in gear this clears the codes and self defense mode. When you re-start there is no longer a slug of air in the system and all is well.

The first time I experienced the "problem" the codes stayed on and the truck high reved to get it moving. It finally after 5-10 minutes of driving returned to normal, but the SES stayed on. Had to take it in to the dealer to clear the code and they did some kind of part replacement that was probably not necessary.

I bitched about it to Big Al and he came back with this solution per above. So anytime you leave your truck sitting for a while the Convertor will leak down, when you start up, a slug of air is the first thing the TCM "sees".

If your ses light is still on you will have to get it cleared at the dealer unless someone has a Tech machine.

So start it up, don't put it into gear, cut it off after 1-2 minutes and re-start, all should be fine.

My truck sits 2-3 weeks at a time when I am traveling. Ever since, I always now start, cut off and re-start and I have never had this problem again.


Good Luck