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Discussion Starter #1
Every month I drive my truck from VA to NY to work, it is parked for 2 weeks and I drive it home.

This most recent time, on the way to NY, I was at cruse (75mph) cc set and I felt a shutter in my butt ( I didn't hear if there was a noise, radio was too loud), looked down and the RPM's had jumped a few hundered RPM. There was no slipping as I pressed the accel (TC was still locked in). I pushed the OD off button, it lit but no change. I pushed the OD on button, light when off, rpm raised a couple hundered (TC unlocked) and went back down (TC locked). I pulled over and check to see if I had run over something (NO) leaks (NO) fluid level (GOOD) and smell (also GOOD). I continued driving, shifting seemed normal, TC operated as normal and had all gears (except OD). I continued on my drive to NY until the last rest area where I stopped and removed the Banks Big Hoss chip and bypassed the Banks Trans Command. Still had good shifts, proper TC functions but no OD.

A few days later I drove the truck to the store (hoping a cold trans would produce something different), everything as mentioned above seemed to be the same except at 40mph the TC lock up seemed to be very unsteady (unlock with the slightest touch of the throttle), which at that speed and cold it was alway a bit quirky. I could not drive the truck long enough to get the engine or trans up to operating temperature.

Now, history on the trans. I have had 4 transmissions in this truck, they have all been Jasper units (upgraded HD over their stock replacements). One lasted about 20k(convertor failure), next 1 was defective out of the box with the convertor locking in in Reverse but still driveable, third had the same issue as the 2nd and a convertor with a big flair after about 30k. Now the
4th trans is in the truck, I installed a Precision convertor (low stall, billet duramax hub, billet body), I also installed a heavy duty power valve to firm up the shifts and switch the convertor lock up to on off vs pulse. This trans has about 50k on it, Amsoil synthetic fluid flushed at 30k and drain and fills every 10k so the fluid is in good shape and looks/smells fine. The truck sees towing regularly, no more than 8k lbs for 300 miles each way about 10 times per year.

There are NO flashing lights, no check engine light, and no noises even after a long period of driving

Another question to go along with "what do you think it is" is do you think it is safe for a 400 mile drive home or should it be towed ($1000)

Thanks!!!!!!!
 

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Very good description of problem. I find it hard to believe you have no od and no codes or flashing od light.
With a no 4th, you need to get someone with a scanner that can read the computer to see if the computer is commanding 4th. If it is and you don't have 4th, you probably have a stuck 3-4 shift valve or 4th is burnt out.
Drive home with od canceled.
 

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Discussion Starter #3
Thanks, I used to be a mechanic for a living then moved on up to svc manager and the heavier trucks were my "teams" expertise and I know the meaning of accurate symptom descriptions. This one really has me baffled, what worries me is the shudder I felt before losing OD as to the possibility of something being broken and causing more for the ride home. I can't pull codes where I am, I work on a tug boat and rarely see land other than to go out and get food or supplies. Since there are no flashing lights I feel a bit better but I still don't have any real peace of mind. Would a stuck 3-4 shift valve cause OD to leave while cruising? I guess if I understood how the valve worked...maybe if the default position was for the trans to be in 3rd. I thought I had read somewhere that there is a snap ring somewhere that breaks and causes OD not to work. Any ideas on that?
 

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The broken snap ring is for the 4th return. Od will still work, for a while, then the snap ring gets caught in moveing parts then destruction. The snap ring may have been broken for awhile and has now done the damage to cause no 4th.
Default is just high Line Pressure. Hard shifts.
 

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Discussion Starter #5
Hard shifts will be a hard to tell diagnosis with the heavy duty power valve in there, as my tranny guy put it "I got 2 I can put in there, this one will knock the needles off the gauges". So that vibration I felt may have been the destruction?? I'm not a good inside the transmission guy, R and R yea but not internals, would you say if it's the snap ring that it would still be ok to drive home (400 miles)? and how much of a job is it to repair that? I guess if that's it there would be no "check" lights whereas if it were the solenoid there would be. I wish I had access to a scanner!!!
 

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I've had vehicles come in for other reasons and needing an o/haul. Take them apart and find the od snap ring out of it's groove. Obviously been that way for awhile but no serious damage to the 4th hub. Take another one apart and find the snap ring in a thousand pieces mangled up in the od gearset, totaly destroyed.
You will need to find out if the computer is commanding 4th to know where to go next.
 

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Discussion Starter #7
Yeah, I know the deal. Just wondering about that $1000 tow bill.
 

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Discussion Starter #9
That's the plan, thanks. I can't believe that a "good" company like Jasper would put a snap ring on instead of the better spiral dealio......
 
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