Allison

Data

Serial #6610067829

In Service Date (Customer delivery): 12/20/2001

GVW 47,000 CGVW 52,000 VW as operated 39,000 CVW as operated 42,500

Cat C-12 power 455 BHP

Cooled through external intercooler by engine coolant – OEM system

4000 MH transmission with shallow pan

Normal refill after draining and fluid change 31quarts, after overhaul 41 quarts

Actual refill after overhaul 44 quarts, actual normal refill 34 quarts (external cooling 3 quarts)

Maintained in accordance with Allison Technical Bulletin #1099 as revised – all maintenance time based, never required by mileage.

Purchased by current owner 10/1/04

Allison warrantee in effect until 12/20/06. No claims on record at Allison.

No problems were noted nor was any work requested by current owner prior to failure other than fluid and filter change at purchase and one additional filter change due to time interval recommendation. Transynd fluid used last 2 changes prior to failure.

Service

Owner arranged for a filter and fluid change with a mobile lube service due to Allison time interval recommendation. Transmission worked perfectly during 3000 mile trip ending 1 week prior to service. Transmission temperature stable between 180 and 190 F. Engine was started and transmission warmed up on morning of service, never exceeding 1000 RPM. Fluid came up to temperature and transmission engaged properly in drive and reverse.

Failure

Fluid was drained and filters replaced by mobile lube technician. Technician stated that 26 quarts of Transynd were pumped in from his bulk tank. The dip stick did show fluid at or near the normal level.

Transmission never regained circulation. Temperature would not increase, transmission would not engage, fault light illuminated, fault code 25-11 was exhibited. Later removal and inspection of filters reveled that the filter cavity never fully filled indicating that very little fluid flowed from the pump after filter change.

Technician removed at least 2 quarts of fluid and continued testing for an extended period of time with similar results excepting for additional fault code 55-99 being indicated.

Fluid Shortage

Additional inspections and testing were accomplished by the owner in conjunction with instructions from Allison Factory Support. All drainable fluid, including the filter bay, was measured and the amount found was considerably short of what the technician claimed to have installed. Calculations indicate that the fluid in the transmission during attempted operation was between 15.4 and 18.4 quarts below normal operating level. That would leave 13.6 quarts in the sump assuming 9 quarts for the converter and 3 quarts for the external cooler. The normal level in the sump is 31 quarts.

Ultimate failure was in the pump and pump drive tangs on the torque converter. Total run time from first indication of failure to tear down was approximately 2 to 3 hours.

Technician's Position

The technician claims that the failure just happened to occur at the moment he started the engine after draining and partially refilling the transmission. He states that he put adequate fluid in and cannot explain the lack of fluid when it was later drained and measured. He insists that nothing he did could have caused this failure to happen in this particular way.

Failure Theories

Three ideas of how failure occurred have surfaced so far. One is that the transmission was run without enough fluid in the sump to charge the pump. The pump overheated and failed. Either by high friction or locking up, the pump caused the otherwise sound tangs to bend and release from the inner gear.

The second idea is that the tangs are noted to be a weakness and they simply bent because of fatigue, wear or faulty manufacturing.

The final is that the pump gear bushing or ground sleeve bushing, whichever term one might use, simply fell out of or was never installed in the inner pump gear. This allowed or caused the tangs to bend causing the failure.

Navigating the Pictures

Many pictures of the failed parts of the transmission are on this website. You can navigate through them by simply clicking next on the bottom of each page. If you wish to skip around click on the name of the particular part that you would like to see. To get back to this page, simply click "Data". If you would like to ask a question or see another angle on a picture please use the email address or telephone number below for that.

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How to Help

Your expertise and references are deeply appreciated. First off, it would be great if you would note your opinion on the failure and perhaps why you came to that conclusion. Secondly, we need someone with extensive hands on experience to state and be able to support the cause of failure. An eventual letter explaining the experts position along with a willingness to testify (very doubtful to happen) would be even greater. Your estimate of anticipated charges for the letter and your future time would also be appreciated. This claim is not against Allison nor against any Allison shop. The technician's company does have liability insurance covering this matter.

If you are unable to write the letter and/or testify, do you know someone who would? Perhaps you know someone who is retired, maybe even living in the southern Texas area, who has the expertise to work on this matter. An Allison engineer with aligned experience or an Allison mechanic, either of whom might have seen this very failure in other transmissions, would be best. Please help put us in contact with that person if at all possible.

Thanks!!!

For your time to look at this and for any help you can provide!

Bruce Benson

bruce@1benson.com

830-992-1406

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