I had an AOD built for heavier service. Gave a major chain tranny shop $2000 to build one with mild shift kit, HD torque convertor, "A" Overdrive Servo, and have installed a thermostat controlled cooler. I was confident that the technician knew his stuff, as he was fully aware of common swap to newer planetary sets, etc. but felt it unecessary for my application.

They assured me it was adequate for occasional towing and plowing in a 5500lb F250 4x4. This is a 2WD unit, used in the highboy remote case configuration. 1 year, 20000km warranty, which I'm about 12000km into.

I have carried a few big loads with the truck, and temp has never been a real issue, except once when carrying 3000lbs over the Rockies, when I had to rest on a particular pass when tranny fluid temp approached 190 F. The unit barely reached 150-160F in any other use.

Tonight I lost all gears save for first and reverse. 2,3 and OD all disappeared at the same instant. On a coast downhill, reaching 50mph, the tranny would not shift into any other gear. It would coast with rpm drop to idle when I let off the pedal. (No engine braking as if manually shifted into 1)

The fluid still looks, and smells absolutely beautiful. The unit did not leak or overheat. The TV cable did not come unattached or out of adjustment, and was set by the shop.

My 300 six is stock on Propane, and doesnt make much power. I do have 4.10 gearing, with 30" tires.

I am very hopeful that warranty coverage will be complete on the unit, and that I may just be on the hook for a tow or so. I did have to drive the unit home for a distance of about 10 miles, first gear only, not exceeding 3200 rpm. (thankfully it was late at night)

I thought long and hard before having this unit built; and resolved when I paid the bill that if I didn't get my money's worth out of this unit while being very careful with it and maintaining it properly - that I would give up on AOD's forever. I'm really thinking I'll do a ZF swap and never look back.

I'm curious if anyone has a thought on what may have happened.

Thanks for any that may read this, and for any insight that might be shared.

 

After much research, I'm hoping my governor has become stuck, or that my valve body has a minor complaint.

Anyone have other ideas where a sudden lack of any upshifting could occur from when no fluid has leaked, and is still fresh and clean, the tv cable hasnt come off or of adjustment and still functions properly, and the unit was not overheated??

Earlier before the event, I tried climbing a steep, rocky hill in 4WD. After putting the truck at a steep angle, I started from an idle went to WOT in my stock 300, and had slow wheelspin from my traction lok rear D60 and open front D44 before giving up and not pushing the matter.

That leads me to think I may have made the governor stick somehow with excessive TV pressure?

 

Well, the unit definitely has something other than a governor or loose valve body problem.

The unit will be pulled, and further work done to determine problem over the next day or so.

Thankfully it seems warranty coverage wont be a problem. The fluid is very clean, as was bottom of the pan, and nobody feels it's an abuse issue.

The tech's first thought is there is a broken band or something. I am taking some interest in the process, and will post with the nitty gritty as it unfolds.