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Discussion Starter · #1 ·
Hello all, I'd like to use your vast knowledge pool to troubleshoot this one. I searched the forum criss cross, but no answer found.

Today I drove on local freeway on cruise control slightly uphill about 70 mph when engine RPM suddenly went up and transmission shifted in low gear and the engine light turned on. I turned off the cruise control and when road leveled off it never shifted to higher gear anymore, seemed like limp mode. I stopped, read the codes P700, P777, P700d, and P777d, then I erased them and waited about two minutes with ignition off.

I started again, the engine light remained off for few seconds then it turned on again, no high gear available anymore. I stopped and read the same codes again.

Then I arrived to the city and in parking lot I realized that I have no reverse gear anymore and the dash underneath the R was flashing. I tried to push the truck out of parking stall, but it would not move backwards with engine running. I had to turn it off, then it was freewheeling again and I was able to push it out.

On top of it, I noticed that when on Neutral the truck behaves like it is in Drive gear. I can step on accelerator and it starts slowly driving forward, only message something like "shifting function immobillized" came on and the dash under N started flashing. When I shifted to D, it behave same and the dash unde D started flashing.

The transmission is Allison 1000 5speed, with ~137k on it, Mobil synthetic ATF and new spin-on filter has about 10k on it. The code P777 says "Pressure Control Solenoid 2 Stuck On".

So here are my questions:

1) Where is this solenoid located?
2) How can I unstuck it free?
3) Any other possible culprit?
4) If the transmission needs overhaul, how much that usually costs?
5) If I need to replace tranny, can I swap this 5speed for new 6speed?

Any other suggestion is more than welcome.

Thank you all in advance.
 

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From what you're describing it sounds like the C4 clutch didn't release when it did a 6-5 downshift. My guess is that there's a problem in the valvebody, possibly a stuck valve.

I'd suggest having someone experienced tear down the valvebody and take a look at it. The transmission itself is likely not bad.

As for whether or not you can change a 5-speed to a 6-speed, you can...in theory. In practice it's another story. Do some searches here there are pages and pages of discussion.
 

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could be a little piece of debris in the valve. the six speed is possible, s/c sells a kit to change everything over. only a valve body and programming. it is pricey though.
 

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Discussion Starter · #4 · (Edited)
Update 12/23/07 - still can't find the problem

Stopped by Allison dealer/service on Friday. Unfortunately, they are booked for next two weeks. They were very helpful though, one technician told me which solenoid it is and how to get to it.

On my way home, I noticed that even in Neutral or Park you can hear the friction noise, like two plates are lightly touching

Drained fluid - it really smells kind of like burned something. Found bunch of small (about 1mm/40 mils) non-metallic debris at the bottom of the pan. Also spin-on magnet had about half teaspoon of metallic dust on it. The fluid is Mobil1 synthetic and there is only about 11k miles on it, mostly freeway.

Disassembled number 2 (or B) solenoid and trim valve. No blocking debris found, solenoid checked working. All the other solenoids are in working order as well. Checked wiring harness - did not see any rubbing or damaged area.

Put it back together yesterday and tried again this morning. Same behavior as before, same codes P0700 and P0777. Only now it seems after few miles driven Reverse can freewheel backwards as before it could not. Also, sometimes it shifts gears normally through gears 1-4, other times it is locked in gear 4 (not sure tough). Can't get to the fifth gear at all.

I am at loss - any advice?

Very Merry Christmas to all!
 

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Discussion Starter · #5 · (Edited)
I opened the valve body and found it contaminated with debris, magnetic chips this time of 1mm x 0.5 mm in size. It seems that something is busted inside and debris keeps contaminating valve body passageways and orifices.

In other words I am in market for rebuilt transmission. I have few questions though:

1) I am not doing any racing, rubber burning or heavy hauling/towing, except 1ton camper for traveling. Should I get upgrade aftermarket rebuilt such as heavier clutch rings, etc. Or regular standard rebuilt would be just fine for my needs?

2) If upgrade rebuilt, which components are must, which optional?

3) Anyone can recommend a reputable outfit which sells quality rebuilt Allison1000 transmissions at reasonable cost? I am located in Northern California, SF Bay Area.

4) Any other suggestion is welcome.

Thank you all!
 

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i would talk to mike L tomarow and see what he says since your in ca and to far compared from where some come from. he will get you pointed in the right direction with the corrrect answers to get you going again
 

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Discussion Starter · #7 · (Edited)
Before I talked to Mike L., my local Allison service shop told me it is too difficult to do it myself. They were booked for at least two weeks and the cost estimate was ~$2000. Mike encouraged me to do it myself.

Got it apart, totally burnt and fused front half of C1. C3 friction plates partially discolored. Replaced them both. Put it together last weekend, put new TranSynd in it and it drives like new so far. Total cost of parts ~$350 including 5gal TranSynd pail of which I used ~3gals.

Did few manual transmissions only some 25 years ago, this was my first automatic. Nice simple design. Since I bought it used, I have no history on it, but am still curious why C1 failed so miserably.

Thank you all for your help, especially to Mike L. for his encouragement.

Sincerely, George
 

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Before I talked to Mike L., my local Allison service shop told me it is too difficult to do it myself. They were booked for at least two weeks and the cost estimate was ~$2000. Mike encouraged me to do it myself.

Got it apart, totally burnt and fused front half of C1. C3 friction plates partially discolored. Replaced them both. Put it together last weekend, put new TranSynd in it and it drives like new so far. Total cost of parts ~$350 including 5gal TranSynd pail of which I used ~3gals.

Did few manual transmissions only some 25 years ago, this was my first automatic. Nice simple design. Since I bought it used, I have no history on it, but am still curious why C1 failed so miserably.

Thank you all for your help, especially to Mike L. for his encouragement.

Sincerely, George
Congrats George. :ro)
Good job my friend. :D
 

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My truck just started doing the same thing today. I'm going to have to tear into it to see what is going on.
 

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I don't think that you'll find the same thing that George did. Never seen this failure with the new high capacity rotating clutch design on the 6 speeds.
 

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Discussion Starter · #11 · (Edited)
To Josh

It happened to me one day, next day I drove it to Allison shop and it was getting worse. During try one, I was just checking the B solenoid function, then put it back together and again it was worse after that. I could even hear faint metal to metal rubbing. The drive was progressively more sluggish. Of course, the reverse did not work at all, and it started pulling forward even on neutral and later on reverse as well. At this point I decided to not to torture it anymore and rebuild it.

Since you have 2006, it should be covered by warranty, if not I'd do it myself as Mike L. suggested. The only 'special' tools you need is engine stand, long arm jack or transmission jack, pair of car stands and large snap ring pliers (both kinds).

Good luck, George

P.S.: my is around 500 miles since the repair and still working ;)
 
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