Hi
I have a 1987 F350 4x4 crew cab 6.9 with a c6. I have not had this truck long it was shifting gears to early right off of the stop into 2nd and 3rd soon after. I thought maybe vacuum regulator so I changed that out with one from another trans I had off of the same truck no change. I took it over to a transmission shop asnd they said it was to much vacuum and turned it down almost all the way off, up by the IP this worked it shifted great but now when I start it up cold it takes forever to shift until it warm up!! I read up on it here and figured out where and how to adjust it and turned vacuum up a bit cold shifting was better but after it warm up back to early shifting. I cannot find a happy place is this a matter of playing with it or the vacuum regulator by IP being bad?? Any advice would be a help thanks.

 

Could be the MLPS manual lever position sensor on the trans is out of adjustment. Have you done a vacuum test....... checked under the juice tin for holes.

Band adjust.....C6

Raise or shinney under the blocked vehicle.
Clean all the dirt from the band adjusting screw
Hold the adjusting screw from turning, remove and discard the lock nut.

Install a new locknut, tighten the adjusting screw to 10 ftlbs torque.
Back off the adjusting screw exactly 1 1/2 turns.
Hold the adjusting screw from turning and tighten the locknut to 35-40 ftlbs.
Lower or shinney out from under truck, remove blocks.

Automatic Transmission Shift Rod or Shift Cable Adjustment... C6 and E4OD

1 Raise vehicle on jack stands or hoist. (I'd block well and scramble under)

2 From inside the vehicle, place the select lever in D/C6 and OD/E4OD . Hang a three

pound weight on the selector lever ( six pack still full)

3 Remove shift cable from the transmission lever ball stud/shift rod.

4 Pull down the lock tab on the shift cable body.

5 Position transmission lever in drive position. This is three detents from the front-most

lever position with the first position counting as one.

6 Connect the cable and end fitting to the transmission lever ball stud/shift rod.

7 Push up on the lock tab to lock the cable in the correctly adjusted position or tighten nut

and bolt.

8 Remove jack stands and lower vehicle from hoist. Remove three pound weight from

column shift select lever.

9 After making adjustment, check for Park engagment. Check the transmission control lever

in all detent positions with the engine running to make sure correct detent/transmission

actions, readjust if necessary. Reset the PRNDL indicator as required.

CAUTION:
Under no circumstances will it be permissible to adjust the cable/shift rod in any position

other than D for C6 or OD for E4OD.

Now all should be ok if it is in PARK and everything works, remove blocks.

Road test...................(drink warm beer)

 

You could adjust the vacuum sensor on the IP lever, turning it toward the front of the truck will delay the upshift, and turning it towards the back of the truck will make it upshift sooner. Very little movement is needed to have an affect.

I don't think the MLPS has anything to do with the shift timing of the C6 trans.

 

Dave your right but my thought was to ensure the linkage to trans and detents were correct and the MLPS/PNP was set correctly..... cart before the horse sorry....

 

The governer in the rear of the trans is speed sensitive, and if it's buggered, the shifting speed will be off.

Also, there are different length rods for the vac modulator.

Too much vac is solved by stepping on the gas to make it shift later, so I doubt that is the problem.

Too little vac (like the hose fell off) will make it act like you have your foot into it hard, and it will shift real late.

 

That is my problem when I get the shift set when it is warmed up and driving it is wrong ( shifting to late when it is cold ) and vica versa. That is my problem.
fordtowman

 

If it was me I would drop the oil pan, drain the torque, install new filter screen, replace pan and fill with new fluid plus a bottle of Lucas trans. conditioner.

 

all of that is new, I think it is a vacuum issue just not sure why. I will do another check of can and lines mybe a leak is causing a longer time to build up vacuum when the vacuum regulator is turned down and making it shift late when it is cold, would that do it?
fordtowman

 

"Conditioner"?

"CONDITIONER"?

Changing the trans fluid for fresher and cleaner fluid would be a better idea rather than adding some crap that should "condition" it!

All it will do is swell the seals in the hope that it will stop one from leaking.

Should I guess you might think on your own what it does to healthy seals?

Wanna know how many transmissions I "fixed" that would not shift because some dope added octane booster and melted the inside of the catalitic converter preventing the engine from reaching enough RPM's to shift?

AVOID SNAKE OILS!!!!!!!!!!!!!!!