C6? transmission problems

[David85]

Originally Posted by dieselutheran21

It dropped from 21 down to about 13, but seemed to hold steady at that. Should the vac lines hold 20+ long after shutdown? The sound didn't start until I unplugged the vac gauge. Also, I didn't have the a/c running (the belt isn't even on the compressor).

So when you unplugged the vacuum gauge there was an open port to the vacuum system? I know my truck (both of them) will hold vacuum in the accessory plumbing for a long time after shutdown - overnight at least, but I never felt the need to measure it so I don't know how much vacuum there really should be.

All I can suggest is try to trace the hissing noise to its source and look for signs of wear on the hoses (or other damage) possibly from rubbing against a bracket or other hard object in the engine bay.

[ford trans tech]

E4OD was not avaiable until 89
if the kickdown rod is connected to the lever on the IP it must have the return spring attached to it so that it will return
if the rod is hanging down under its own weight it will prevent upshifts also just as you described
if you cannot connect the rod correctly , simply disconnect it from the transmission by remocing the e clip
if the rod is depressing the lever it affects the upshift
after eliminating it then check the VRV valve
all VRV valves are the same 6.9 or 7.3
and make sure your vacuum pump is making vacuum check it with a gauge at the VRV valve supply line while the engine is running

[dieselutheran21]

Thanks for the info on the kickdown rod. I've purchased a new VRV and will install/calibrate it tomorrow. plus, i'll disconnect the kickdown rod because I'm sure it has been bent (it is a strain on both the IP and the tranny). I'll connect it to the IP and leave it off the transmission lever. I'll post again tomorrow night an let you know how things progess.

[dieselutheran21]

With the VRV installed, engine running, I set the VRV position to produce 13 in/HG at idle. I unhooked the kickdown rod and put 1/3 qt of dex/merc in the transmission and took it for a test drive. I adjusted the band tensioner and put a new locknut on. I also unhooked the vacuum lines for the cruise control from the "T" and plugged the port (trying to limit the possible sources of vacuum leaks).

The truck still wraps up pretty high before shifting into third, and kind of wallows around (as if in a false neutral) for a bit, but actually stays in 3rd gear instead of jumping around. Since I was limited to city streets for the test drive, I'm not positive that it is completely sorted out. I will know better tomorrow. With the truck on a gravel driveway, in "D" with the brakes held down the truck will spin a rear wheel (so the transmission isn't slipping, it actually engages).

Which of the two measurements on the VRV is most important? 13in/Hg at idle or 7 in/Hg w/.515" block? The reason I ask is because neither the brand new VRV that I got nor my old VRV was able to have both. Right now I have my old one on, and it actually holds a vacuum (WTF?) whereas the new one (once mounted on the truck) doesn't (2xWTF?). Can these be bench-tested or must they be dynamically set on the truck? While driving it 40+ miles from storage tomorrow, what should I keep an ear/eye/feeling out for? Thanx

[dieselutheran21]

I've been doing some more searching on the modulator. Seems mine has a green stripe, but on some other forums it has been mentioned that diesels should use the black stripe, and high altitude uses white stripe. I ask because I will be moving to Colorado soon, and be at 7000 ft elevation. Should I put a different color modulator in? Someone with specific transmission rebuild manuals and knowledge, please chime in.

[dieselutheran21]

Well, this will probably be the last post on this thread as there seems to be waining interest. The truck worked fine today. It shifts at 2500 rpm, which seems okay. The "gas" pedal feels really tough to push, quite a workout. The truck drove about 50 miles today up to 70mph without any major problems. Minor problems include no cruise control and the aforementioned stiff pedal feel. It might be a little low on power, I'll try advancing the IP timing a little to see if it makes any difference. It smokes a little white smoke on hard accel, but other than that I'm pretty pleased with how it worked today. I gave it a bath as a reward for doing a good job today. Thanx everyone for your help, I couldn't have done this project without your help and FTE! Great job everybody!

[David85]

Hey buddy, I'm still interested!

I still think you could have a vacuum leak in there some where since you say the cruise doesn't work (servo uses vacuum to pull the throttle cable).

Assuming there isn't a vacuum leak, have you tried adjusting the VRV to bring the shift RPMs down? (rotate in the direction of throttle movement to lower RPMs). Or is it already at the limit?

[ford trans tech]

your post isnt waining , some of us only have a couple of times aweek to get on here
i suspect you have a broken throttle cable causing it to bind , correct that issue first then on to fine tuning your vrv valve adjustment , there are differences in the modulators alright but should be fine with the green stripe , the green stripe caused issues when used behind 351 GAS ENGINE

[dieselutheran21]

Throttle cable pull - how many springs are on the IP to return the throttle linkage back to idle? Mine has 2.

What engine speed should the truck shift at? When accelerating from a stop fairly quickly it seems to shift at the right time, it's just rolling around in town that it gets a little annoying at 2300rpm in 2nd at about 40.

How long should the vacuum system hold the vacuum, which the vac pump is producing at about 21-24 in/Hg? I haven't yet tested it for leakdown in it's current configuration.

Part of the interest that is waining is mine, as I only have 2 weeks from today to move. Time to get serious and write some papers for school!