C-6 shifting wierd

[bigrandy]

Hello all!I'm new here and have been reading as much as I can on here.Great site by the way!!I have found more info on this site than all the others I have looked at combined.
Well I have an 85 F350 crewcab with an 88 7.3 in it.I just bought the truck from a buddy and he had just had the engine and the turbo rebuilt,an ATS, about 10k ago.I bought the truck about a year ago and proceeded to gut the running gear and installed the axles from a 91 f350 and lifted it 4".
Since I have been lurking on here I figured out how to turn the pump up and what a difference.Anyway last week the vacuum pump took a dump on me so i replaced it.Now the tranny shifts at way too high RPM's.I have the factory service manual and I readjusted the VRV to spec but it hasnt changed! Does anyone have any ideas.It shifted fine before the vacuum pump debacle,it also downshifts to 2nd gear at 40 mph now and that is also a new problem.Any help would be much appreciated.
Randy

 

[Agnem]

Check the color code on the shift modulator (where the vacuum hose goes on the trans). Possibly the PO changed that out trying to fix the low vacuum problem. Alternatively, put a vacuum gauge down there and see what you have. Usually late shifts are due to low/no vacuum.

 

[LCAM-01XA]

Adding to what Mel said, most vacuum modulators for the C6 are adjustable, you take a small allen wrench and slide the long leg ofit in the modulator's vacuum port and then you can turn the internal spring preload dohicky - IIRC turning clockwise raises shift points, and turning CCW lowers them, so you can play with that if you wish. Tho in your place I'd be very very tempted to get a full-manual valve body with the reverse shift pattern and install a slapstick and call it good, as a matter of fact the only thing stopping me from doing this to my own truck is the fact no one out there makes manual VBs for the E4OD...

 

[ameristar1]

Adding to what Mel said, most vacuum modulators for the C6 are adjustable, you take a small allen wrench and slide the long leg ofit in the modulator's vacuum port and then you can turn the internal spring preload dohicky - IIRC turning clockwise raises shift points, and turning CCW lowers them, so you can play with that if you wish. Tho in your place I'd be very very tempted to get a full-manual valve body with the reverse shift pattern and install a slapstick and call it good, as a matter of fact the only thing stopping me from doing this to my own truck is the fact no one out there makes manual VBs for the E4OD...

Lentech or Baumann don't make manual valvebodies?

 

[LCAM-01XA]

Nope, not for the E4OD.

By the way, your flat top is much like my flat top, which years is that KW?

 

[bigrandy]

Thanks for the help guys I will be putting a vacuum gauge on the line.Down right at the tranny right?I will check that stripe also.I was thinking that maybe the PO had done something to compensate for a weah VP.
By the way how dark should my exh smoke really be.I turned the pump up 2 flats and it is a medium gray when you lay on it pretty good but the pyro never gets above 650?Seem a little low to you guys.

 

[LCAM-01XA]

Yes, pull the hose off the vacuum modulator, and put the gauge in the hose there.

As for the EGTs, where is your thermo-probe installed, before or after the turbo? You want it before the turbo, preferably in the exhaust manifold, this will give you the most accurate readings.

 

[bigrandy]

The probe is pre-turbo.I put a gauge on the line and got 22" of vacuum.I cant find anything for color on the modulator-entirely too much grime.Guess I should clean it up a little huh?Anyway I guess I will try to turn the spring dohicky and see if that helps.Thanks guys.

 

[LCAM-01XA]

22" vacuum is what, the reading at idle? Have you tried giving it more throttle to see how the vacuum readings are dropping? IIRC 22" sounds about right for idle, but verify readings at part throttle and WOT too, to make it easier to see the gauge you can hook it up directly at the VRV's outlet (follow the hose up from the trans).

 

[bigrandy]

Well I called the PO and he told me he had indeed adjusted the modulator to fix the shift points.I readjusted the mod and it shifts just like it used to.Thanks for all of the help.

 

[LCAM-01XA]

Oh, goodie

 

[WrickM]

this is a good thread find for me. My shift point have gone up recently. doesn't seem to want to shift before 2500 rpms 1-2 and 2-3. check the tranny fluid which was a little biut low but nothing to get in a pinch over. added some and it shifted a little better but still not where it feels like it should be.