I'm starting to think my transmission is trashed. Truck has no forward or reverse movement. Whenever I unplug the connector on the back of the trans I still have no movement. My fluid is bright red and I was told by the mechanic there was clutch material in the pan, but "not enough to amount to anything". I read that the C1 and C2 apply pistons are off centered so when they wear out they're only 50% worn, so this would make me think there isn't going to be much shavings in the pan. The code I have now is P0841. I've previously had codes P0700 P0732 P0743 P0776 P0802 P0841 P0843 since the initial brake stand incident. Limped it home after slipping through all gear lightly accelerating. Truck would hold higher gears 4-5 just fine with heavy throttle, but not from 1-3 without slipping. After that, I lost all forward movement and soon after lost reverse. I've replaced the PSM, internal filter, external filter a month ago, TCM, ignition switch, and I'm replacing the NSBU tomorrow. On the scan tool, the tow/haul enabled/disabled was reversed from what it actually was, the gear ratio displayed was 0.00, pressure switch C wouldn't command on, and the truck is locked in 5th gear. It does have good line pressure though. Any help would be greatly appreciated because I'm not getting much help from my mechanic. I would take it to another shop, but there are none closeby.
C1 Clutches Toast
- Thread starter zachw677
- Start date
The ohms checked out to spec. I will check voltage again to make sure. Shouldn't I have forward movement though with the trans connector unplugged? The plug is leaking out of the bottom row of pins, but if you spray it out and put dielectric grease on it it doesn't change a thing.
If the c1's were gone it would still have reverse unless the pump is out or output shaft or all the clutches are gone. Mine would run like hell in rewind but no go in drive.
I went to brake torque and put it in 2nd and it shifted from 1-2, 2-1, then on the 1-2 shift it went into neutral with "Range Shift Inhibited" and I had to restart the truck to get it to move. Instantly if you gave it any acceleration at all it would rev up high and move but not as much as it should for the RPMs. If you gave it even 1/2 throttle it would go to neutral but still barely moved once you slightly accelerated. I continued to drive it like that home. Once it built up speed, I could put it into neutral then back into drive and it would shift into a higher gear where it would hold just fine with whatever acceleration. After a few stop signs it was stuck in 2nd and wouldn't shift higher. The next day it only had first that would slip anything over 1/4 throttle and reverse which seemed to hold fine with whatever throttle. It continued to do that until I loaded it on a trailer where it the lost all forward movement. After I got it to the shop he said it lost reverse.
I have trashed my c1s and the truck would still move and shift OK while up shifting but second i let it start downshifting it'd bind up and lock the rear tires up for a sec and then limp out..... and stick in 4th. Done that 2 times now completely smoked c1s that concaved and everything lol.
I'd imagine you have something else happening to not just c1s
Have you checked pressure to see what your building? Does it load the motor down when you put it in gear?
I'd imagine you have something else happening to not just c1s
Have you checked pressure to see what your building? Does it load the motor down when you put it in gear?
New NSBU and cleaned all grounds, still nothing. He talked to another mechanic that said one of the spool valves could be stuck in the upper valve body. He's taking it out and going to check today. I told him to make sure the trim valves had 12V also. Will post update later.
Just to clarify, if you unplug the connector at the rear of the housing, it does nothing, correct? No forward or reverse?
What I was getting at earlier was, if you unplug that connector you should have 3rd and reverse through hydraulic default. No electrical input is needed to have 3rd and reverse. Unless of course you have a stuck valve or a solenoid is stuck or something like that.
But if you have no gear engagement at all with the connector unplugged you have internal problems.
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What I was getting at earlier was, if you unplug that connector you should have 3rd and reverse through hydraulic default. No electrical input is needed to have 3rd and reverse. Unless of course you have a stuck valve or a solenoid is stuck or something like that.
But if you have no gear engagement at all with the connector unplugged you have internal problems.
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Then at a minumum the valve body needs to come out. I would get a pressure gauge on it 1st and see if you have line pressure. If you have pressure with no movement, then the fun begins.
Sorry it took so long. I just heard back from him today. After cleaning the valve body and checking all the wires he thinks the transmission is shot. Apparently he doesn't rebuild Allison's, so it looks like I'll be pulling the trans and tearing into it. Thanks for all your guy's help!
That's what I'm saying. I don't know why he even agreed to look at it if he doesn't know anything about Allisons. Apparently he got reverse to work again and it's creeps in drive now like it used to. Throwing a P0731 now and staying in 5th gear limp mode. I'm just assuming the C1s are fried.