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Wet tank air has to be continuously supplied to the unloader pistons to ensure the compressor stays unloaded till tank pressure drops below the governor set point - if the unloader piston o-rings leak then wet tank pressure will drop till the compressor reloads. Unloader piston leaks can cause...

Yep. Pretty much guaranteed nearly everyone on this forum has exhaust valve springs that look exactly like that. Except me of course.

Also - just for grins - you should check the connector pin "drag" on the male/female pins for the bus on the truck side connectors - sometimes people overlook pin-fitment issues with connectors and they may have good connection to the wiring but poor grip on the TCM pins inside the connector...

Well - yes you could do that and probably should do that given it sounds like you don't have a diagnostic solution - the real first step and where I would go now is to hookup a laptop (or something like the Bluefire adapter and a phone/tablet) and see if the data it wants is actually on the bus...

Interesting. You are right there is not. I was thinking of vehicle speed. Vehicle speed is exchanged outside the bus..... I have witnessed more than one truck driving without the J1939 bus operational so the TCM must be switching over to the J1708/J1587 bus for that information or it has a...

Ah I see. That makes more sense. No worries. Sorry about the communication gap. Have you tried having him type it up using Google Translate and then proof-reading what it spits out? Just a thought.

Sorry - Colloquial terminology for the CANBUS architecture - they are labeled J1939 Data Link (+) and J1939 Data Link (-) And yeah - the trans computer is learning I'm assuming. Unfortunately these do shift/TC lock/unlock hard and the CAN communication error is highly unlikely to be related...

Well the next step now that you know the bus is intact is to test for that same resistance at the TCM truck side connector CAN Hi and Lo pins. That will be at the WTEC III controller itself under the passenger side of the dash.

It's on the back. The level is filled till it flows out the fill plug. Drain is on the bottom.... How did you check that is has oil if you don't know where the fill plug is :rolleyes:

Probably needs to be a lot more than a ton. Mine was still noticeable on the 2-3 shift even with the WTEC IV, ATF, and the 3,400 lb 1079 box on the back. Maybe 2-3 ton? IDK. The TCU gets it's TPS from a dedicated ECM output. It does not use the bus for anything other than diagnostics that I'm...

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Any J1939 bus wires going to any termination resistor or module. Easiest is probably the bus termination resistor next to the engine ECM - with that one unplugged you should see 120 ohms and the resistor itself should be 120 ohms. Or you can front probe the databus connector on the dash. Just...

That means the Allison computer has problems with it's J1939 bus communication. The FIRST thing to check is the resistance between CAN Hi and CAN Lo pins on the harness. If the coms bus termination resistors are blown, damaged, or missing that will take down the bus - probably the most common...

NEVER take an FMTV to a shop. YOU ARE THE SHOP. Or forget it - buy a Land Cruiser and accept that It's All Over But The Crying.

Could be the starter. Have you *tested* the batteries that you charged? What is their voltage and have you done an actual load test? 12v is dead. 12.6v is fully charged. Many people have trouble with this. I've been bitten myself by this. Even a battery that reads 12.6v can still be bad. Only an...

Pull your batteries and full charge them out of the truck. :rolleyes: While that is happening in the background. Clean EVERY ground on the truck. Especially the ones from the battery box to the frame, the frame to the alternator, the frame to the cab (just replace it), and the frame to the...

The oil pump is shot. I would stop running it under load till you get the oil pump replaced. The pumps were redesigned by CAT several times and the relief valves on the pump are weak in addition to changing from a gear pump to a trochoid (gerotor) pump and the idler gear bushings/bearings...

How many miles and how often do you drive it? What's your oil pressure and have you checked out the HEUI injection actuation pressure stability? What are you ultimately planning to do with the truck? For most of us, ECO hubs are a very good idea for drivetrain longevity.

It's just a 24v, 100A continuous duty solenoid. Any brand/country of origin you are willing to live with will work in theory. Google some up, note down some part numbers, and start calling suppliers in your area. Factory is a Prestolite..... NSN 2920-01-361-5802 Part #'s 12414619 BAE 19999220...

Don't worry about simplifying till you address the early HEUI system, superceded engine oil pump, and cleaning/servicing every electrical connection and everything rubber on the entire truck. Beyond that - there are many threads on how to remove the LBCD, change over to a commercial alternator...