I really really hate to even ask

[MACKIN]

But I'm gonna do it under my better judgment.

My truck has been doing more sitting then walking. Occasionally it's a simple start and quick move perhaps 10 feet then returned ti it's resting spot.

I did drive it 150 miles last Friday on a part scavenging hunt. Details details

So It's been sitting every since NO movement. Well today I had to move it the 10 feet I refereed to earlier.

Here's what happened.

I fired it up and with in I dunno 10 seconds dropped it from park to drive. What I received in return was NO engagement. Lightly pressed on the throttle notta. Up to reverse,nottta. Back to park

I then dropped it back into Drive and it engaged also reverse.Moved the truck out seemed ok. Didn't actually drive any where. Checked fluid ,fine.

Three things come to mind.

Converter drain back,why? It shouldn't do that.
Snuck up on it?
Running a Napa T filter. Restricting flow?
And the worst of all is a C1 issue.

The ATS has been flawless up to this.

 

[GMC_2002_Dmax]

Drive it in bad weather, it will help stop the leaks by getting it dirty.........

Seriously, sounds like it drained back on ya.

 

[duratothemax]

minor drain back, dont sweat it pops.

 

[SIKDMAX]

Mine engages hard after sitting for more than 3 or 4 days..... similar situation?

 

[pmeg1]

The ally 2000 series in my tool truck (same neutral safety switch) had the same symptoms awhile back. It seemed to happen randomly but was accompanied by a range inhibit or check trans light. At first once a month, then once a week etc. New NSBU switch and all was well.

 

[McRat]

That's normal especially on 2001 LB7's.

 

[Drholliday]

I doubt its a c1 issue b/c it did it in both reverse and drive.

 

[duratothemax]

I doubt its a c1 issue b/c it did it in both reverse and drive.

C1 is used in both reverse and first.

 

[bigbird]

My dads did the same thing and it was the NSBU switch

 

[malibu795]

after itting for a few weeks (when it was running) shifting and gear engagement was funky... done it a coupel times.. i let is idle for a few minutes.. alows all the fluid to circulate and re-saturate stuff..

some time with the parking brake engage and tranny in gear

 

[MACKIN]

Hard to believe it's TC drain back as it only sat for 6 six days but I could only hope that is all it is. Time will tell

 

[Brayden]

C1 is used in both reverse and first.

C3/C5 are used in reverse. It's the only range that doesn't use one of the rotating clutches.

 

[Steve O]

Mackin,

My vote is Drain Back .. Sitting 5 days is when this problem usually happens..

The reason I kinda rule out the NSBU is because if this was the problem it should happen every time you start it up cold.. This does not seem to be the case??

 

[C.A.P]

Nsbu..........

 

[Mike L.]

I would also check sump filter for looseness.

 

[duratothemax]

C3/C5 are used in reverse. It's the only range that doesn't use one of the rotating clutches.

doh nvmnd my bad..thanks Brayden

I was thinking mistaking it for C5, the common pack between 1st and reverse

I should know; last one I did I put the entire C5 pack in upside down. Needless to say I didnt have 1st or reverse. 2nd 3rd 4th and 5th worked great though!

 

[RayMich]

Is there a fix for the converter drain back?

Is this a problem on the 6-speed Allison also or is it only on the 5-speed?

Thanks.

 

[Mike L.]

Is there a fix for the converter drain back?

Is this a problem on the 6-speed Allison also or is it only on the 5-speed?

Thanks.

Allison fixed it in '03. Transgo shift kit has the fix included in the full shift kit.

 

[RayMich]

Allison fixed it in '03. Transgo shift kit has the fix included in the full shift kit.

Thanks, Mike.