I have a 460/C-6 in my F250 that sat in my trailer for about 3 years before installing and its never shifter right since,at first it wanted to start out in second and now its starting out in first and going right to third. It will shift manually just fine so I am thinking sitting for 3 years got something to stick so anybody have any ideas.
I have a C4 in my 72 F 100, and it does the 1 - 3 shift under light throttle driveaway,.....It's done that from Day One; <I bought the truck new> I'm not sure exactly how different the C 6 is, from the C 4... Yes, mine did the manual 1-2-3 thing every time too. Anyone else experience this ? 4TTRUK
I would get it warmed up, drop the fluid and filter, install a new filter 'n fill 'er up and hope for the best. Bob
My thoughts are It is Either the modulator or the vacuum line going to: it might be ported off of or from the wrong/intake/carb/tee/Vacuum source. Or vacuum line to the modulator is leaking and/or loose connections/vacuum leak.
When I installed the motor and trans it got a new modulator and fluid change but that was 3 years ago and it sat around while I was doing body work,I will check the va***n line to the modulator tonight after work for leaks. I was only able to drive the truck on and off for 3 months before tearing it apart for body work and then it did not move much for the next 3 years,I am thinking about trying another valve body since it sat with very little fluid for the first 3 years and could probably use a good long drive to get hot before doing anything drastic.
I just went out to the garage and looked on how the modulator was hooked up and it and the booster are hooked to a port on the intake that is getting va***n from one cylinder so I need to do some plumbing,its got a performer intake and only has va***n ports coming of single cylinders so I need to come up with a carb spacer with a pcv port. I am wanting to get rid of the cheesy chrome valve covers and hook up a closed pcv system to the mustang dual snorkel aircleaner so I have some work to do and will see how it does after I get it all changed.
Changed some va***n lines around to where they would get va***n from all cylinders and will go on a test run after I throw some burgers on the grill.
Doesn't seem you understand much about the vacuum on your motor. There is no such thing as vacuum from only one cylinder. Your booster and modulator were hooked to a vacuum tree behind your carb. That vacuum tree is manifold vacuum from all 8 cylinders. If you pull a cap off it you'll feel suction when your motor is running. Your pcv will be needed to be hooked to another manifold vacuum source. Should be one large one on your carb. You might not need that spacer. On a normal pcv system you have a pcv valve on one valve cover and a breather on the other cover which can be open or hooked to your air cleaner. The other type of vacuum is ported vacuum. When your motor is running if you pull a cap off a ****** on your carb and there is no vacuum suction then that is a ported vacuum port. Burn us off a pic of your motor so we can critique it!
The edelbrock performer intake that is on the motor only has two ports for va***n and both are on a single intake runner,it might draw va***n from all 8 cylinders but I dont think it would do so evenly. Most of the stock intakes I seen have a port right behind the carb that would draw off all 8 cylinders but this Edelbrock is not that way and the holes for the va***n ports are almost to the head,I plugged the port the booster and trans was hooked to and ran the booster to a extra large constant va***n port on the carb and the trans to the smaller constant va***n port on the carb. It did not change the way the trans is shifting so I must have something sticking in the valve body but the brakes seem to be working better now.
I don't think the vacuum would make it shift 1-3. Maybe shift real high if there's not enough vacuum or 1-2-3 at low speed if there was too much (not likely). When you put the new modulator on did you make sure the modulator pin was there. If not it might be sliding right through 2nd into 3rd. Hope this helps.
I am going to let the guy who rebuilds my trans take it for a drive and see what he thinks,I cant remember how it shifted when in the donor truck so it could have been doing it then.
If your vacuum is hooked to the wrong port, it will shift into high gear faster than normal. In fact, the harder you put your foot down on the gas the faster it will get into high gear. Otherwise, it is probably the modulator, not expensive and still available.
If the vacuum is not there it will be a very late high rpm shift it cant have to much vac but the modulator can be adjusted with a screw inside to shift sooner the kick down linkage can be adjusted to the govenor has weights that stick and will cause those shift problems
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