700R4 Skips 3rd Gear

[howardjnl]

We have a 1985 K5 w/6.2 diesel. It recently began to "skip" 3rd gear, going directly from 2nd to 4th with a slight hesitation between the two gears. It does not rev up as if 3rd is slipping.

ALSO, if shifted manually, using the gear shift to select the gears manually as go up the gear range, it shifts just fine up through all 4 gears. Anyone have any ideas to offer on this one? Thanks in advance.
John

 

[Kjunky5]

If you don't have 3rd, you wouldn't have 4th either. You might be confusing lock up for 4th. But first check the T.V. cable for proper operation and adjustment.

 

[Thunder]

Sounds like the TV cable is out of adjustment.
How long has it been since the pan has been dropped and the fluid/filter changed?

 

[howardjnl]

All of the usual stuff: fluid and filter changed June 2009 and again two days ago after problem began (still have problem). Very familiar with TV cable adjustment, all is well there.
More info: problem does NOT occur when is WARMED UP, only when cold. Does indeed go from 2nd to 4th as originally described (when cold), but does go into 3rd just fine when cold as I manually shift upward through the gears. Found some metal shavings in transmission pan when changed filter this time.
Will next look at condition of the governer.
Wondering:
1. how to tell what is causing the shavings (torque convertor or transmission),
2. why problem only occurs when cold,
3. why problem only occurs when let transmission shift itself upwards automatically but not when shift manually,
4. how can skip only 3rd but all other gears work fine?

Thanks for feedback.

 

[Kjunky5]

There is an odd but possible problem. The pan gasket can cover or almost cover the 2-4 servo exhaust hole if installed wrong. If the fluid can't exhaust quickly or at all would cause it to remain applied and that would make it feel like it went straight to 4th since the 2-4 servo is applied in both. This is very rare but possible. That's why there is no separate accumulator for 3rd gear. It uses the stroke of the servo pin when 2nd releases for a "cushion". If you are 100% positive you have 1, 2, 4, and lock up then I would say it has something to do with 2nd not releasing. Since like I said, if you lost 3rd you would also lose 4th.

 

[Kjunky5]

1. how to tell what is causing the shavings (torque convertor or transmission), Some "shavings" are normal friction material collecting as the transmission ages. If you just noticed big unusual pieces than I would say you've got a problem
2. why problem only occurs when cold, Cold fluid=higher viscosity=higher line pressure
3. why problem only occurs when let transmission shift itself upwards automatically but not when shift manually, More is going on when manually shifting. Higher line pressure, overrun frictions applying. low/reverse frictions applying (only in 1st)
4. how can skip only 3rd but all other gears work fine? 2nd and 4th use the same servo and band, different ways to apply it, but same servo and band.

 

[howardjnl]

Kjunky5, Thanks very much for your detailed replies. We're working finr now, here's update on what transpired:

Let truck set for a week during much rain.
Took out for a test drive to re-evaluate symptoms, but now only had reverse, neutral and 1st gear working.
Pulled governer to do visual check for any obvoious problems, none seen. Put back in.
Discovered many posts on the internet about not being able to get out of first gear with 700r4's, supposedly a common problem.
A recommended "fix" was to manually (by hand) work the TV cable in and out many times with engine running and in neutral to clear possible blockage. Did that.
Next road test it started out still not working, but revved it up and down a few times while driving and very quickly cleared the problem. Had tried this second step before, but did not work. Looks like the manual messing with the TV cable plus the revving up and down together did the trick.
Now everything works fine, even the original missing 3rd problem is gone. Must of been some bit of something going through the fluid lines.

Thanks again! Hope our experience is helpful to others.
John

 

[howardjnl]

Just a quick update: After two different 700R4 transmissions, each being rebuilt twice, the second transmission has totally crapped out a third time. Some folks think a 700R4 behind a high torque engine, particularly a diesel, is too much for a "not beefed up", standard 700R4. I'm tending to think that myself now. We've converted over to a NV4500 manual transmission, and this should damn well last us. Have two 4x4 700R4's in need of rebuilds in my garage to dispose of :-)
John

 

[tRustyK5]

I have a 700R-4 behind a 6.2 diesel in my '83 pick-up. It's definitely not the later updated and better version of the 700R-4, but it's original and works fine even at 155,000 miles...

Rene