Hi Transmission temp after tranny service

[DougBrsrd]

Took the little Princess into the shop for some service work last week. In addition to setting valves I had the transmission serviced. When driving home transmission temp gauge went to 300 degrees F.

Eng is Cummings L10 with 4 speed Allison transmission on 91 Monaco signature.

Have only taken one road trip - over a 1000k miles prior to this and temp never went over 160 degrees F.

Called the shop and they are going to send a tech over to look at the problem on Monday.

Any ideas of what could have gone wrong. At idel cooling fans are working at low speed and there is fluid showing on the dip stick?

Thanks for any help

[JimM68]

somehow, the new filters, or something related to them, is restricting the flow of fluid through the trans. Hopefully the shop who did the service can fix it up quick and before real damage occurs. For sure do not drive it!

[DAN L]

Originally Posted by DougBrsrd

Took the little Princess into the shop for some service work last week. In addition to setting valves I had the transmission serviced. When driving home transmission temp gauge went to 300 degrees F.

Eng is Cummings L10 with 4 speed Allison transmission on 91 Monaco signature.

Have only taken one road trip - over a 1000k miles prior to this and temp never went over 160 degrees F.

Called the shop and they are going to send a tech over to look at the problem on Monday.

Any ideas of what could have gone wrong. At idel cooling fans are working at low speed and there is fluid showing on the dip stick?

Thanks for any help

someone else had a similar problem recently.
do a forum search.
irc the problem was a too short filter installed in a deep sump tranny. the filter was not retained properly and soon fell off into the sump.

[Midniteoyl]

For sure do not drive it!

Agreed, Do NOT..

[scgator]

Have only taken one road trip - over a 1000k miles prior to this and temp never went over 160 degrees F.

This tells me your transmission "should" be in good mechanical and operational shape; without know the actual mileage of this rig, let me ask a few questions and give a few pointers. I am a former ASE Master Mechanic (Heavy Duty Class 8 Vehicles).

Tip#1 Unless you currently have a transmission problem, NEVER change your transmission fluid....NEVER ! The reason is that internally what actually makes the transmission move is fluid pressure applied to one or more "clutch packs". This is series of alternating disks contained together within a clutch housing......i.e. you will have a metal disk then a fiber disk, then another metal and so on until the pack is complete. As fluid pressure builds, this clutch pack begins to "work" causing the transmission to begin to utilize the power coming from your engine causing your vehicle to move.

In order for transmission to build operating system pressure, they have very tight and precise internal clearances; some as close as .003 thousandths of an inch. The fiber disks in the clutch pack, being softer than the metal will wear away material as the years go by and this "residue will remain in the hydraulic system of the transmission as floating debris. I call it debris as it is no longer attached to the face of the fiber disk. IT DOES NOT HURT ANYTHING ! It actually helps you to retain the close internal clearances. If you flush and service your system, you are washing away this debris that is still resting in between the clutch disks; this physically "increases the clearance" between the disk. This in turn allows the fluid pressure begin to drop slightly and reduces the fluids ability to dissipate heat from the fluid. Thus as a result, temps go up and the higher the higher the temps, the fiber disks will prone to crystalize (harden) and this will reduce their ability to transfer power. In other words, your transmission will begin to slip. The only cure is a rebuild at that point.

By experience, we have an '04 Dodge Hemi Quad Cab with 160K on the odometer and have NEVER serviced the transmission. Our TT weighs in at 8000# and we have been in the snow and in the heat of Texas and never had any issues.

Tip#2 When the mechanic arrives, he will first look for leaks, fluid level and then air restrictions at the cooler.........if all of these check okay, tell him you want a transmission pressure test performed (there are test ports on the transmission for this). If all of the previous tests are okay, and the pressure test shows "low" then the problem is in the clutch packs of the transmission.......this is simple cause and effect mechanics.

Tip #3 Another poster commented about a filter restriction issue; you did not mention any driveabilty issues, and a restricted filter would cause shifting and or performance issues........so at this time I would rule it out.

Good luck, hope everything works out okay on Monday.........if you need to PM me it is okay to do so.

[hzjcm8]

I disagree with never changing the fluid !!!

[DougBrsrd]

Thanks for the posts - will provide resolution hopefully tomorrow.

db

[chief02]

Ok, so you say NEVER change the fliud, what say you about the filter? And how do you change an internal fliter without loosing fluid? Or do you capture the old fluid and put in back in? Hmmmmmmm.

[Midniteoyl]

The only time I wpould say not to change a tranny's fluid is if you never have.. Say like 100k miles... And precisely because of that 'debris'..

If, however, you have followed the recommended change interval, or even close to it, you now need to continue doing that..

[Dwight]

Take care of your Allison and it will take care of you.

If you don't want to change the oil, don't do it.

I have been using Allison Transmissions for so long that one of the first ones had the serial number stamped -Experimental-.

[Damon Outlaw]

Originally Posted by hzjcm8

I disagree with never changing the fluid !!!

I agree. Follow your vehicle's or fluids recommendations. I do use a full chemical synthetic transmission fluid to lower transmission temperatures, better mpg and protection, and longer service life.

[scgator]

Originally Posted by hzjcm8

I disagree with never changing the fluid !!!

Even Toyota and Nissan Motor Companies (Aisin is their transmission builder) does not recommend changing transmission fluids unless it is because of a mechanical repair......and they are offering a 100K warranty on their vehicles through the dealers.

I understand your point though; I have rebuilt a lot of powershift transmissions and Allison transmissions that are used in heavy equipment and off road applications. Honestly, in these applications, the most common cause of failure has been "old age", not mechanical or system operation failure. Today's transmissions are much more durable than most people realize.

And I don't want to offend, but if I were in the lubricant anlysis business, I too, would want people to use more of it; and would heartily disagree with anyone who did not feel the same way about fluids.

In reference to someone's post about changing the filters; if the transmission has an external filter, then by all means change it at a designated interval (the reasoning is that an inline filter has more propensity to restrict as the flow rate is greatly reduced in proportion to inlet and outlet capabilities). If it is a sump filter, I would not worry, they are not filters in the true sense of the word, they are strainers, which is a totally different animal. Strainers do not have the finer micron "filtering' that actual filters do. They are simply used to reduce the possibility of larger debris from being pulled up into the ports of the valve body and spool passages or orifices. A sump filter is used to strain the oil that passes through it, while an external filter is designed to clean the oil that passes through it under system operating pressure.

When you take your RV to the shop, having your mechanic run a simple pressure test on the transmission will tell you EVERYTHING you need to know about its internal condition, and it usually costs only about an hour's labor charge. I will agree, that fluid analysis can be a valuable tool...if your equipment operating conditions are severe. An RV running down the highway is not severe conditions. They are normal conditions that Allison and other First Class manufacturers take into consideration when designing their end product.

Fluid analysis on a diesel is more practical as it can determine if there are slight traces of coolant in the oil thus indicating a liner starting to pit because of cavitation; or it may indicate an internal leak in an aftercooler or injector cup around an injector.

But it is what it is............before I retired, I was a top rated mechanic in my field (who consistently worked hand in hand with engineers on testing). Some will agree with me, some won't..........the bottom line is YOU do what you think is best for you; it is your RV, your money, and your peace of mind. It is just that I have learned and taught too much ( I taught advanced hydraulics design and theory at a major DOE Nuclear Facility for three years) over the years to not know something substantial. I have "remanned" at least 50 powershift, Aisin, and Allsion transmissions and likewise rebuilt over 200 Cummins diesel engines "blueprinted" back to factory specs............ALL with a ZERO failure rate. When I was first certified by Cummins in 1979, I finished the testing as #2 in the state of Georgia, and recertified a few years later, tied for #2 in the state of Georgia.

My philosophy has always been...........LEARN TO DO IT RIGHT, LEARN TO DO IT THE WAY IT WAS ENGINEERED, AND NEVER SACRIFICE THE QUALITY OF THE END PRODUCT........AND YOU WILL ALWAYS HAVE A JOB. I could not afford the luxury of college as we had three kids early in our marriage, so it was up to me to learn on my own....and that I did.

[bluefox]

On mine I have a remote filter and this is the only one I changed.

[hzjcm8]

Originally Posted by chief02

Ok, so you say NEVER change the fliud, what say you about the filter? And how do you change an internal fliter without loosing fluid? Or do you capture the old fluid and put in back in? Hmmmmmmm.

Chief02(Bill),

I agree and I am speaking from many years of experience as the Transmission Fluids Engineer for Allison Transmission where I observed many transmission fluid tests and my position on the GM ATF Committee where I observed many more transmission fluid tests. I can tell you, for instance, that the GM 4L60 transmission will typically fail the 1-2 shift in the DEXRON-III Cycling Test. This is due to a combination of friction surface distress, fluid oxidation, viscosity change, and the loss of friction modifier additive.

Most ATF formulations are designed to give good oxidation resistance; however, most are very bad at maintaining viscosity. GM DEXRON-III and Ford MERCON ATF were (and still are) notorious for losing viscosity in not too many miles. Most of today's ATF market are unlicensed products called D3M or multi-vehicle ATFs. These fluids are also subject to loss of viscosity with use and you can only find this through oil analysis. Viscosity loss leads to bushing wear because they get so thin that they can no longer generate the oil film required for these highly loaded parts. Also, ATFs can become contaminated over time with system debris (like you talked about) and also with with internal coolant leaks. If coolant gets into a transmission, it can chemically attack the bonding materials that hold the friction material onto the friction plates. If they do oxidize, the oil molecules become "polar" and will tend to stick to clutch plates changing the coefficient of friction resulting in a slipping clutch and eventual elongated shifts, increased shift energy density and failure of the clutch material due to excessive heat. Friction materials contain such things as cellulose, Kevlar, fiberglass, silica (sand), etc. that can damage bearings and gears if the particles are large enough. When particles are very small (say around 5 micron or smaller), this leads to silting and silt can lodge behind valves and cause malfunctions, sticking valves, scoring of valves and valve bores ..... etc. The simple fact is that all ATFs wear out. The rate depends on the original fluid quality and the amount of mechanical and thermal stresses the fluid sees over its lifetime.

Allison recommends oil analysis because its the only way to see these phenomena. You do need to change the fluid but only when oil analysis detects a problem. Once a year is enough to detect changes in most RV service since mileage accumulation rate is typically low. Allison didn't release any design without validating it with component testing, transmission cycling tests and fleet tests and they all had oil analysis as proof that the system and its components were working properly without excessive wear and that the oil was holding up to the recommended change intervals. That was the whole purpose of TranSynd. DEXRON-III fluids lost viscosity and engine oils didn't have enough oxidation resistance so the TES-295 specification increased performance for both of these parameters.