Trans / T-case temperature gauges

[MrGoldman]

After my C6 failure in my first transmission I'd like to add some way on the dash to monitor transmission and transfer case temperature so I can understand how its doing befored it comes to the warning light.
I live in Colorado and drive in the mountains a lot and plan on towing with my 1998 A0 truck (3116) Wtec 3.

Has anyone added analogue or digital gauges and where did they put the sensors? My best idea for the transmission is to remove the fluid sampling port in the front and put it there, I havent looked at the transfer case yet.

Looking at something like this:
52mm Digital Dual Display Temperature Gauge-℉ - Rico Instrument

Matt

 

[Ronmar]

I added engine and trans oil temp gauges to my dash but have not added the sensors. i was also looking at utilizing the oil sample ports as the trans port is on the cooler supply line so overall trans output oil temp.

the engine sample port appears to be post cooler but it is convenient

As for the transfer case, there is an access cover in the middle on the rear face to get at the output speed sensor. Pull it and take a look there. If memory serves there is nothing immediately behind that cover and it could probably be drilled and tapped for a temp sensor. Now where the running oil level in the transfer case actually rides in the sump, I have no idea as I do not know where the scavenger pump internal gallery is actually routed from the port where the screen and hose are located... Since it is capable of picking up to P6 thrust bearing parts it may pull oil from quite low. All those parts, after they thrashed the P6 clutch and housing components, exited the P6 housing thru its drain hole right down near the bottom of the P6 case gasket… from there some found their way to scavenger suction, and some usually find their way down to the transfer drain plug

since you are about to have a core to disassemble, you could answer these questions?

read back thru the threads on these failures and analyzing the pics and diagrams a little more, these failures are either happening when the P6 is released or when thru vibration/acceleration bring the center carrier(~7#?, plus the clutch component weight) back against the thrust bearing. The piston is all the way in the back and has a hole in the middle for the center tower of the housing. It is held in battery by a spring pack secured to the center tower with a large snap-ring. When pressure is applied it pushes forward compressing the springs and the fixed and rotating discs to lockup the center carrier and center shaft. This will push the carrier away from the thrust bearing. When P6 is released the center springs retract the piston leaving the carrier and discs to slide to the rear and contact the thrust bearing. Since the transfer case main gears are helical, there may be some other dynamic involved here like shifting between forward and reverse that causes P6 plate carrier movement to the rear, as the nose/snout of the carrier protrudes forward into the output shaft rear carrier bearing in the back of the transfer case under a cover

The pressure lube to the P6 enters the center rear of the housing from the left side of the transmission(piston pressure is applied from the bottom gallery). lube flows past the center shaft bushing in the center housing tower, then passes thru the space between the stationary center tower and rotating plate carrier. That is where the thrust bearing is located. Oil then flows thru small holes in the carrier and out amongst the rotating and stationary clutch discs or out the back of the cupped center carrier and down past the piston face to the bottom of the case. The thrust bearing appears to be well lubricated…

The root cause of course is that Allison put a 1/8” thrust bearing into a 3/8” cavity next to a heavy component that was allowed to move freely…

working on lifting my hab floor today to pull my P6 assembly and put a bushing in where the roller thrust is…

 

[Skyhawk13205]

After my C6 failure in my first transmission I'd like to add some way on the dash to monitor transmission and transfer case temperature so I can understand how its doing befored it comes to the warning light.
I live in Colorado and drive in the mountains a lot and plan on towing with my 1998 A0 truck (3116) Wtec 3.

Has anyone added analogue or digital gauges and where did they put the sensors? My best idea for the transmission is to remove the fluid sampling port in the front and put it there, I havent looked at the transfer case yet.

Looking at something like this:
52mm Digital Dual Display Temperature Gauge-℉ - Rico Instrument

Matt

I think the databus has a temperature reading. One popular option is the bluefire system. You can see a trend rather on relying on an idiot light.

I added engine and trans oil temp gauges to my dash but have not added the sensors. i was also looking at utilizing the oil sample ports as the trans port is on the cooler supply line so overall trans output oil temp.

the engine sample port appears to be post cooler but it is convenient

As for the transfer case, there is an access cover in the middle on the rear face to get at the output speed sensor. Pull it and take a look there. If memory serves there is nothing immediately behind that cover and it could probably be drilled and tapped for a temp sensor. Now where the running oil level in the transfer case actually rides in the sump, I have no idea as I do not know where the scavenger pump internal gallery is actually routed from the port where the screen and hose are located... Since it is capable of picking up to P6 thrust bearing parts it may pull oil from quite low. All those parts, after they thrashed the P6 clutch and housing components, exited the P6 housing thru its drain hole right down near the bottom of the P6 case gasket… from there some found their way to scavenger suction, and some usually find their way down to the transfer drain plug

since you are about to have a core to disassemble, you could answer these questions?

read back thru the threads on these failures and analyzing the pics and diagrams a little more, these failures are either happening when the P6 is released or when thru vibration/acceleration bring the center carrier(~7#?, plus the clutch component weight) back against the thrust bearing. The piston is all the way in the back and has a hole in the middle for the center tower of the housing. It is held in battery by a spring pack secured to the center tower with a large snap-ring. When pressure is applied it pushes forward compressing the springs and the fixed and rotating discs to lockup the center carrier and center shaft. This will push the carrier away from the thrust bearing. When P6 is released the center springs retract the piston leaving the carrier and discs to slide to the rear and contact the thrust bearing. Since the transfer case main gears are helical, there may be some other dynamic involved here like shifting between forward and reverse that causes P6 plate carrier movement to the rear, as the nose/snout of the carrier protrudes forward into the output shaft rear carrier bearing in the back of the transfer case under a cover

The pressure lube to the P6 enters the center rear of the housing from the left side of the transmission(piston pressure is applied from the bottom gallery). lube flows past the center shaft bushing in the center housing tower, then passes thru the space between the stationary center tower and rotating plate carrier. That is where the thrust bearing is located. Oil then flows thru small holes in the carrier and out amongst the rotating and stationary clutch discs or out the back of the cupped center carrier and down past the piston face to the bottom of the case. The thrust bearing appears to be well lubricated…

The root cause of course is that Allison put a 1/8” thrust bearing into a 3/8” cavity next to a heavy component that was allowed to move freely…

working on lifting my hab floor today to pull my P6 assembly and put a bushing in where the roller thrust is…

Ron, amazing description of the oil flow path and C6 operation, I have been trying to figure out the oil flow path for the C6 and transfer case for a while via a part breakdown and the WTEC trouble shooting manual.

here is a multitude of question to waste your time on

Do you think the thrust bearing gets damaged from shock loading during a specific shift?

Per the WTEC TSM the only time the C6 is pressurized is in 1st gear. The WTEC TSM does not really cover the C7 and transfer case operation. Is the C6 pressurized differently in mode?

Do you think shock loading is reduced with ECO hubs?

What driving habits would reduce wear to the C6?

Have you seen any reports of a C6 failure on a 6x6? I suspect that vibration is a key driver to the accelerated failure of the C6

Thank you very much for your contribution here, I know that you have saved me much time in diagnostics and research.

 

[Ronmar]

“Do you think the thrust bearing gets damaged from shock loading during a specific shift?”

Perhaps. the P6 carrier and plates appears to just be free floating in there. You know that 2-3 shift that trys to bounce your eyeballs of the back of your skull? That might have something to do with it? The only shift I see directly interacting with it is the shift out of 1st gear… but again not sure of all the possible interactions. They did leave a heck of a large gap where that bearing is located…


“Per the WTEC TSM the only time the C6 is pressurized is in 1st gear. The WTEC TSM does not really cover the C7 and transfer case operation. Is the C6 pressurized differently in mode?”

no, the P6 comes from the main transmission control module. It is programmed into the mix to activate the P6 as part of the shift into 1st Just like the other clutches used for other gears.

The only thing mode does is give you a gear range preselect(1-5 instead of 2-7) and alters the shifting parameters slightly. I have one report so far of the trans holding lockup down into 1st gear when using an ex brake while in mode. When not in mode it lifts the ex brake and uncouples the torque converter lockup in 2nd. Mode also outputs a mode indicator signal to drive a dash light. In our case that indicator signal is rolled right back into the transmission as an input signal(the A0’s use a VIM relay, the A1’s simply hard wire it). That input signal tells the trans to lockup the center differential via a solenoid valve in the transfer case. Center diff lockup also has an output/indicator signal. The LMTV uses that signal via a relay, to control the air solenoid that locks up the power divider on a 6x truck. So button requests mode, mode request AWD to 4WD, and 4WD request 6X on those three axle trucks. That was how I added a 4x4 switch to my dash. I will probably use mode with the exhaust brake


‘Do you think shock loading is reduced with ECO hubs?”

Yes, the 2-3 shift is certainly smoother as the torque converter being more heavily loaded does not accelerate and the lockup clutch does not engage as quickly. halving the driveshaft RPM also reduces longitudinal(fore-aft) vibrations on our very steep driveshafts. Longitudinal vibration is a side effect of transitioning from one angle to another and back using only a 4 point U-joint. This relationship causes the mass to shift forward and aft with each revolution and cannot be balanced out. Our rear shaft is at the maximum length(61”) for this size shaft and with a thick wall has as much mass as you will find in a type 16 driveshaft. Longitudinal vibration is the reason there are angle vs RPM limit charts, that with the 2:1 hubs, we are exceeding by nearly a factor of 2… eco’s bring us back into the acceptable RPM at our angle and are perhaps one of their greatest benefits. Will this effect the P6? hard to say, but it is sure gentler on the shafts, and pinions.


“What driving habits would reduce wear to the C6?”

not sure as we don’t know if driving habits effect it in the first place… force = mass X acceleration. The P6 carrier can slide, and with all the discs can probably weigh upwards of 30#, so rapid acceleration may cause accelerated contact. Shifting out of 1st releasing the clutch pack may cause accelerated contact. Driveshaft longitudinal vibration may cause intermittent contact. The problem could be the bearing repeatedly being spun up to full RPM from a standstill every time the carrier makes contact… hard to say what kills it…


“Have you seen any reports of a C6 failure on a 6x6? I suspect that vibration is a key driver to the accelerated failure of the C6”

None that I can say for certain, i was involved with a discussion here and the gentleman had just got a 6X and was experiencing trans overheating and i think binding when he first started rolling. After the very detailed description of this latest failure, that person may have also had a P6 failure. If the P6 discs are damaged and cannot spin freely amongst the stationary discs it is like trying to drive with 1st and whatever other gear engaged simultaneously and binding discs and loaded gears = heat.


“Thank you very much for your contribution here, I know that you have saved me much time in diagnostics and research.”

Your welcome, good karma is not a bad thing