Trans Temp Issue

[o1marc]

So I pick the bus up in Louisville yesterday at 5:45pm. 1/2 tank of fuel, so I pull in and fill it to overflow. Get on the freeway and start checking gauges, everything seems in line. 180 water temp, 200 trans temp, 14v, oil pres-50psi. Trans ran at 200 for a bit, then slowly started to creep up till the needle was just about to hit the red square at 280. I figured if it hit the red square or a warning light came on I would need to pull over and cool it. after about 100 miles I decided to pull in and let it cool while I got a hot chocolate to keep from being drowsy, still 6 hours to go. The temp dropped to about 260 and stayed there for a few miles and then started to drop back to 200 where it remained for the remainder of the trip. There was only one hill that heated the water temp some to 200. Bus ran flawlessly, 9.5mpg. Gear goverened to 60mph @2600rpm.

Any ideas on the trans temp issue? Fluid levels checked on departure.

[cadillackid]

what engine what trans? any check engine or shift inhibit or check trans lights?

[o1marc]

Originally Posted by cadillackid

what engine what trans? any check engine or shift inhibit or check trans lights?

2002 Cat 3126B/Allison 2000.

Absolutely nothing out of the ordinary, except that needle on 280. Water temp never raised while it was there. Bus ran fine with no hesitations. No warning lights or anything.

[banman]

Did you recheck the xmsn fluid level when it was good and hot?
While it was hot did you pull the dipstick to give a color and sniff test?

Need to get over 300'F to start really compromising the fluid...
Assuming the bus came with a decent synthetic fluid fill.

An IR temp gun would aid in verifying the actual temps on the xmsn case, compared to the temp sensor which I'm assuming is in the lower section of the case...

[o1marc]

Originally Posted by banman

Did you recheck the xmsn fluid level when it was good and hot?
While it was hot did you pull the dipstick to give a color and sniff test?

Need to get over 300'F to start really compromising the fluid...
Assuming the bus came with a decent synthetic fluid fill.

An IR temp gun would aid in verifying the actual temps on the xmsn case, compared to the temp sensor which I'm assuming is in the lower section of the case...

Assuming you knew a cause, what would fix that on it's own? Fluids were all checked before take off.

[mmoore6856]

i found on quite a few a restriction to oil flow caused a build up of heat. usually a bad filter was the cause. look for any place it could be restricted. even saw a high pressure hose coming apart on the inside of a few. even had a new mack truck once that had the filter lines reversed and the rubber under the small holes had to blow out as they had the oil going into the center. so look for any restriction also

[cadillackid]

a scan tool is the real way to see if theres a trans issue or not.. the allison *SHOULD* set a code if its temp really goes that way and invoke the "hot" program which favors less shifting and always-locked converter..


is your lockup working? as others mentioned.. drive the bus then shoot the pan and the trans case wit ha temp gun and see what you get..



change the little spin-on filter and see what you get results wise then..

[brokedown]

> I got a hot chocolate to keep from being drowsy

Someone lied to you, that's not how it works!

But seriously, back to the transmission, I'd be suspect of the trans filter. The trans fluid is doing double duty both hydraulic fluid and coolant, if the filter is restricting the fluid your temp would rise similarly. With that said, being a 'new to you" bus, i'd also suspect the gauge and the temp sensor. if you're gonna make a habit out of this (too late) you should spend a few bucks on a scan tool.

[cadillackid]

my scan tools have been some of the best $$ ive ever spent.. and I have a garage full of them... even recently used an OBD1 tool I built years ago to help fix someone;s C60 with TBI on a 366 tall deck!

[o1marc]

Originally Posted by brokedown

> I got a hot chocolate to keep from being drowsy

Someone lied to you, that's not how it works!

What do you mean that's not how it works? Isn't that why people drink coffee, for the caffeine in it to keep them alert? Hot chocolate has caffeine and I was wide awake after drinking. If anyone lied, it was by body.

[PNW_Steve]

Professor Google says that the average cup of hot chocolate does have 5mg of caffeine.

Coffee is a bit higher at 95mg.

You just have to drink more hot chocolate to get your caffine

[banman]

Originally Posted by cadillackid

my scan tools have been some of the best $$ ive ever spent.. and I have a garage full of them... even recently used an OBD1 tool I built years ago to help fix someone;s C60 with TBI on a 366 tall deck!

Sorry -- off topic post...
Christopher-
Before I forget -- I've got a Tech2 clone working nicely -- I got it for maintaining my Saab but it's mostly a GM affair as you probably know.
I'm realizing you're the man to be able to program PCMCIA cards for it.
Backwards engineering to run 16bit software on a virtual Win98 is where my stone tablet & chisel mentality start to come through...

But you're welcome to borrow this thing most anytime based on your reputation here.

[o1marc]

How does one diagnose an issue that is no longer there?

[banman]

Originally Posted by o1marc

Assuming you knew a cause, what would fix that on it's own? Fluids were all checked before take off.

As said: fluid restriction from partially clogged filter is most likely cause.

Gauge -- any electrical restriction will cause an erroneous reading as the gauge works off temperature changing the ohms in the sending unit.

Sending unit itself like anything that cycles low/high/low in it's normal use/operation: after time and use cycles, it can 'wear out' giving an erroneous signal to the gauge.

If you're keeping this bus for sure have the codes run like Christopher suggested. I'd also grab an oil sample when you change the filter and send it off to Blackstone labs to see what condition the fluids in.

[o1marc]

Originally Posted by PNW_Steve

Professor Google says that the average cup of hot chocolate does have 5mg of caffeine.

Coffee is a bit higher at 95mg.

You just have to drink more hot chocolate to get your caffine

I'm naturally awake, never drank coffee. All the coffee I drank in my life would not fill a cup. Doesn't take much stimulant to get me going. I grabbed a big cup, when you hit the hot chocolate button it dispenses a dose of chocolte and then fills the rest with hot water. I push the button till the hot water starts and then stop and start over 3 or 4 times till the cup is full. That gives me a loaded hot chocolate. There's no way I would have made the next 6 hours without it.

[banman]

Originally Posted by o1marc

How does one diagnose an issue that is no longer there?

That's tough -- the shittyist part of "my day" is having to sign off a write up (acft logbook) "could not duplicate"
and the aircraft goes back out to fly...

But an oil sample and code reading will tell you if the oil ever got dangerously cooked. If it did -- then there was a mechanical problem -- may still be a problem...

If no mechanical evidence of a problem than it's more of an electrical problem -- gauge failure in and of itself is not catastrophic, the loss of good information can cause the operator to damage the equipment...

[brokedown]

I am unreasonably dependent on caffeine.

[PNW_Steve]

Originally Posted by o1marc

I'm naturally awake, never drank coffee. All the coffee I drank in my life would not fill a cup. Doesn't take much stimulant to get me going. I grabbed a big cup, when you hit the hot chocolate button it dispenses a dose of chocolte and then fills the rest with hot water. I push the button till the hot water starts and then stop and start over 3 or 4 times till the cup is full. That gives me a loaded hot chocolate. There's no way I would have made the next 6 hours without it.

I have been drinking strong coffee every morning for 40 years. I did quit for a few months a while back and my first cup of coffee, after three months without, gave me a serious caffeine buz. Jitters and all.

[o1marc]

I find it strange that the trans temp went up, but the water temp never varied.

[banman]

Originally Posted by o1marc

I find it strange that the trans temp went up, but the water temp never varied.

Again: after your systems are all warmed up after a hwy run, an IR temp gun (decent enough but cheap at HF) will be able to tell you the fluid temps of the tranny at the case, at the hoses going in and out of the tranny cooler.
You can check for hot & cold spots on the radiator or cooler -- this can tell you an individual tube is blocked for example -- a very handy diagnostic tool if you understand what you're looking at.