Hello Guest

Author Topic: LB7 Allison transmission issues  (Read 2278 times)

0 Members and 1 Guest are viewing this topic.

Offline TexasRedNeck

  • punching bag for moderator humor
  • Registered
  • **
  • Posts: 7031
    • View Profile
LB7 Allison transmission issues
« on: July 22, 2015, 10:48:07 PM »
And an update on the LB7 transmission drama. As you know it was built by Calvins 3 years ago and only has 7,000 miles on it.

Drove home from the weekend place and it ran fine for 130 miles at 75mph. Getting off the freeway and pulling up to the light it would not move when the light turned green. I was able to get it to barely move by revving it and I limped it the 1/2 mile to the house. No movement to speak of forward but reverse was solid and fine. (remember that)
A buddy with really expensive software (read actual Allison software) helped me scan it and we got a solenoid C error code. We dropped the pan and tested the solenoid and the manifold pressure switch while we were at it. Bought a solenoid and pressure switch at the dealer.

Dealer swears the old pressure switch that has 6 pressure switches has been superceded with a newer model (found on the 2004+ year models) and even though it only has 4 switches it is the correct switch and will work with no programming.

Install the parts and it throws different codes??? Moves forward but in limp mode and has reverse. I forget which codes, but they didn't seem to make much sense. So we assumed it might be the internal wiring harness which was original and the wires were pretty brittle. Amazon to the rescue.

Drop the pan again and install the harness...no dice. Same codes and still in limp mode (4th and reverse)

So we start questioning whether the newer pressure switch manifold is correct. Some googlefu and we find articles saying, "yes" its the right part and then we call an "expert" at Stewart and Stevenson who says yes, right part, but TCM needs to be reprogrammed.

Since I still have the old manifold pressure switch and we never really determined that was part of the original problem, we decide to reinstall the original PSM. Drop the pan again (did I mention I'm getting really good at this by now???) and install the old PSM.

Fire it up and no codes! Yippe!....but wait. I now have no reverse, no codes and it drives normal in all forward gears. NUTS!

Start running the diagnostics....looking for TCM connector pins out of whack, 30 pin harness connector on the transmission, etc. Nothing abnormal. It can only be the TCM, the connections in the harness, or the PSM.

So I order another PSM off Amazon and this time make sure it is not the new superceded part, but the original 6 switch style.

Comes off the big brown truck and, you guessed it, I drop the pan again. Did I mention I can get that thing off like a NASCAR tire change?? The fact that its got a 12 inch lift and I don't have to do anything other than roll under it helps.

Install the new PSM, and all of a sudden....it runs normally. Reverse and all forward gears. At this point I'm clueless as to why, and what fixed it, but that was a lot of drama chasing gremlins.

At this point, I really believe there is something not right about using the updated PSM on the older transmissions. No one can explain why, but once I changed it out, the codes went away and the reverse gear came back.
Kids today don't know how easy they have it. When I was young, I had to walk 9 feet through shag carpet to change the TV channel.

Joshua 6:20-24

Offline Sammconn

  • A Guy in the Sticks
  • Registered
  • **
  • Posts: 2604
    • View Profile
Re: LB7 Allison transmission issues
« Reply #1 on: July 22, 2015, 10:54:22 PM »
Glad it's sorted. Hopefully for good.
That is a whole lot of practice. So how fast are you now? Lol.

Good tidbit of info too to avoid stealer intervention.
I just don't want to wind up missing a digit or limb.  I can sometimes get in a hurry to get results.
Sam

Offline Dawg25385

  • Registered
  • **
  • Posts: 2039
    • View Profile
Re: LB7 Allison transmission issues
« Reply #2 on: July 22, 2015, 10:56:26 PM »
Glad you got er back up and running!


Sent from my iPhone using Tapatalk
2006 Chevrolet 2500 HD 6.6
Prov 27:17, 2 Tim 1:7
NRA Life Member

Offline TexasRedNeck

  • punching bag for moderator humor
  • Registered
  • **
  • Posts: 7031
    • View Profile
Re: LB7 Allison transmission issues
« Reply #3 on: July 22, 2015, 11:05:05 PM »
That is a whole lot of practice. So how fast are you now? Lol.

fluid out, pan dropped, internal filter off, PSM off, new PSM on, filter on, pan on, filled with fluid. less than 20 minutes.
Kids today don't know how easy they have it. When I was young, I had to walk 9 feet through shag carpet to change the TV channel.

Joshua 6:20-24

Offline Sammconn

  • A Guy in the Sticks
  • Registered
  • **
  • Posts: 2604
    • View Profile
Re: LB7 Allison transmission issues
« Reply #4 on: July 22, 2015, 11:58:20 PM »
That is a whole lot of practice. So how fast are you now? Lol.

fluid out, pan dropped, internal filter off, PSM off, new PSM on, filter on, pan on, filled with fluid. less than 20 minutes.
Well, that is fast. NASCAR style for sure.
I just don't want to wind up missing a digit or limb.  I can sometimes get in a hurry to get results.
Sam

Offline EL TATE

  • Moderator
  • ***
  • Posts: 2197
    • View Profile
Re: LB7 Allison transmission issues
« Reply #5 on: July 23, 2015, 10:56:14 AM »
Dang Gina! I'll remember this one for sure, thanks for going through the hassle for me.
Husband, Father, Gear guy, Patriot.

Offline Nate

  • Administrator
  • *****
  • Posts: 3831
    • View Profile
Re: LB7 Allison transmission issues
« Reply #6 on: July 23, 2015, 03:14:06 PM »
RN, I am not saying that calvin does or does not know what he is doing, and that mike l does or does not know what he is doing, but have you tried to give him a call and see what he says?
Nate

Give me coffee for the things I can change and Bourbon for the things I cannot!

Offline TexasRedNeck

  • punching bag for moderator humor
  • Registered
  • **
  • Posts: 7031
    • View Profile
Re: LB7 Allison transmission issues
« Reply #7 on: July 23, 2015, 08:26:39 PM »
I didnt talk to mike l but my buddy called him.  I'm not sure they communicated effectively because the answer didn't seem to fit. All in all here is what I think happened.

C solenoid tanked.  Caused slippage and clutch material was deposited in the PSM causing the switches to fail.  When I replaced the C solenoid and the PSM, the C Solenoid was fixed but the new style PSM caused a 1713 code, which is related to the PSM.  When I reinstalled the original, the reverse switch was not functioning due to the clutch material.  Replacing with the new "old style" PSM solved the problem
Kids today don't know how easy they have it. When I was young, I had to walk 9 feet through shag carpet to change the TV channel.

Joshua 6:20-24

Offline KensAuto

  • Global Moderator
  • ****
  • Posts: 4989
  • Just call me Bounty.... always absorbing abuse
    • View Profile
Re: LB7 Allison transmission issues
« Reply #8 on: July 24, 2015, 10:44:01 AM »
That sounds right. The whole "new style updated blah blah" never made sense to me. Having to reflash the tcm to accept the new style would make more sense tho.
Underpaid and misunderstood since 2014

Offline TexasRedNeck

  • punching bag for moderator humor
  • Registered
  • **
  • Posts: 7031
    • View Profile
LB7 Allison transmission issues
« Reply #9 on: July 25, 2015, 08:38:02 AM »
That is a whole lot of practice. So how fast are you now? Lol.

fluid out, pan dropped, internal filter off, PSM off, new PSM on, filter on, pan on, filled with fluid. less than 20 minutes.
Well, that is fast. NASCAR style for sure.
it helps when the truck is tall enough that you can place a 2.5 gallon used amsoil jug with a funnel in the mouth directly under the drain so you can capture the fluid without jacking up the truck. . Then just take that jug and use it to refill.
« Last Edit: July 25, 2015, 08:38:59 AM by TexasRedNeck »
Kids today don't know how easy they have it. When I was young, I had to walk 9 feet through shag carpet to change the TV channel.

Joshua 6:20-24

Offline Sammconn

  • A Guy in the Sticks
  • Registered
  • **
  • Posts: 2604
    • View Profile
Re: LB7 Allison transmission issues
« Reply #10 on: July 25, 2015, 10:45:31 AM »
Yes the 12 inch lift makes the bottom stuff a whole lot more accessible.
Probably a bit more of a pain having to do all the top side off of a ladder.

But Dang 20 minutes is fast!
I just don't want to wind up missing a digit or limb.  I can sometimes get in a hurry to get results.
Sam

Offline OldKooT

  • Registered
  • **
  • Posts: 1412
    • View Profile
Re: LB7 Allison transmission issues
« Reply #11 on: September 01, 2015, 10:44:28 AM »
Congrats on the fact it drives properly now. That said this is why I refuse to buy anything with wires LoL
Norm

Are you a prepper?  "No, whats a prepper? I am just a mildly OCD farmer"

Offline Flyin6

  • Administrator
  • *****
  • Posts: 21124
    • View Profile
Re: LB7 Allison transmission issues
« Reply #12 on: September 01, 2015, 03:37:07 PM »
Congrats on the fact it drives properly now. That said this is why I refuse to buy anything with wires LoL
Really!
Such a good idea!
Site owner    IS 6:8  Psalm 91 
NSDQ      Author: Distant Thunder

Offline JR

  • Global Moderator
  • ****
  • Posts: 7080
    • View Profile
Re: LB7 Allison transmission issues
« Reply #13 on: September 03, 2015, 02:39:15 AM »
Yeah, when ALLYs run, they run good. These darn things have more wires and sensors than a 20 years old car!!

At least you have the selector switch out side your pan, the LBZ and later are inside.

Good job and I was thinking MikeL all the time too.
Retired LEO  Lifetime NRA+  Outcast in Calif

"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants"

Thomas Jefferson