1999 7.3l poor shifting shifts when let off gas

[ipz2222]

After all the known problems with the diode, you put another one back in there?? And please don't call replaceing a few clutches and a diode a "rebuild". Preston

[Star Gazer]

I have a (Dec '99 build) 2000 with 55k miles. F250 4x4. Problems only when I pull a small 5000lb travel trailer/ parachute

On several occasions it would stick in first and not upshift. Most of the time it is after I get off a hwy, and stop at the ramp and start up again, then I leave it running for a while to cool down the tranny, at least that is what I think I am doing?

Then once while going up a few hills in WV it would not upshift even at speeds upwards of 35mph.

The only common element is this happened when it was summer, and I had been running pretty hard, or had bad head wind. I have taken 2 other long trips in winter and never had the issue.

I just installed gauges last week so I have no idea what temp reading where during this times. And I have a 50hp TS chip but have had the problem occur with and without the chip installed.

Anyone had these symptons? Would I fall into the bad diode time frame?

Thanks,
Dean

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Last edited by Star Gazer : 01-13-2007 at 07:30 PM.

[ipz2222]

'00 and'01 are the years for the bad diode, but I don't know the build dates yet.
Usuallly when they quit working, you have no 2nd at all. They usually explode.
Sounds like you may have a sticking 1-2 shift valve. Service your trans "change fluid and filter" and add either Lucas or Lubeguard. DO NOT use any other brans of trans additive. These 2 can be found at O'reilly or Auto Zone. Preston

[Star Gazer]

Hi Preston,

I made an appointment with the Ford Heavy duty truck service dept. He said they will drop the pan, inspect and check for loose screens, restrictions to the cooler, and change filters, and he mentioned a bypass valve of sometype too.. Also said they use synthetic fluid so is a additive still a good idea?

Thanks

[ipz2222]

If they use synthetic, I would still add the Lubegard. Preston

[MNWoodcutter]

I have 2002 f-350 7.3 with 136,000 miles. My truck just started the same thing. Shifts right out of first, into second no problem, then I lose momuntum and the RPM goes to 3,000. Then it shifts. I know I am getting some slip. Could it be the tow safe program from superchips? What is this mechanical diode and where is it. Internal or external. Torque converter or tranny just tired?

[ipz2222]

"Mechanical diode", one way clutch. Three different names, sprag, roller clutch, mechanical diode. The easiest way to understand this is a bicycle. When you pedal forward, the one way clutch engages and turns the wheel, when you stop pedaling, the wheel continues to turn without the pedals turning. That is a one way clutch. 1st, 2nd and 3rd all have one way clutches operating in this transmission. There are 2 for 1st, 2 for 2nd and 1 for 3rd in operation. Add that up and you get 5 but there is actually only 3 in the trans. Some are used in multiple gears.
Did I mention it also has 5 clutch packs, a band and 4 valve bodies?
Loss of the intermediate mechanical diode will cause a loss of 2nd gear, not 3rd. Preston

[DJM]

My truck is kinda doin the same but it's when it goes into the overdrive gear gotta let off the gas for it to shift only happens sometimes though Only got about 9 months on this tranny.

[Badfish740]

This sounds EXACTLY what my trans has been doing lately. So I should change my fluid and filter and use some lubeguard and go from there?

[stroker27]

Originally Posted by ipz2222

And please don't call replaceing a few clutches and a diode a "rebuild". Preston

preston, please dont spell replacing with an 'e'.

point is, do it once its a mistake, do it twice your an idiot.
if everyone was a transmission technician, we wouldn't need this forum