ptharris4990

Hi all,


I got an 86 f150 with with a 300 and a c6 a few months ago and have been slowly getting her road worthy again.


When I bought the truck it had some mean vacuum leaks that have since been taken care of (to the best of my knowledge). When I bought it, it was also not shifting up until you let off the gas. Some of the members here suggested that it was a vacuum issue which may go away when I got the leaks taken care of but it hasn't.


I replaced the vacuum modulator which helped a bit but it is still not shifting on it's own most of the time. It will shift at partial throttle fine but it won't shift at WOT. Trying to run through the gears manually doesn't change anything, it still only shifts when I let off the gas. The fluid is pink still, it was a little low and I added more but if anything this made it worse in the past day or two. Every now and again I'll drive the thing and it will actually shift OK but I've been tinkering with so much little stuff it's hard to keep track of what adjustments affect it and how.


Other info that I don't think is relevant but wiser men may: The automatic choke (on the original feedback carb) was destroyed when I got it so I rigged up a manual cable in the last day or two, the PO removed all of the emissions features except the cat (EGR pipe, O2 sensors, smog pump), I advanced the timing a little bit since the removal of all of the emission equipment messed up the ignition pretty bad.


I'm in SW PA so it really sucks when I'm stopped at the bottom of a big hill and have to get up it in first.

Braggs

Hi ptharris4990,

Here's a few ideas:

• While the engine is running, take off the vacuum hose to the vacuum modulator and make sure you have vacuum there. (put your finger on the end of the hose)
• When you replaced the vacuum modulator, did you put the pin back in? (I made this mistake and it caused similar problems)
• Check your kickdown cable linkage. On Fords, when you push the accelerator, it pulls a lever that turns a shaft on the driver's side of the transmission which rotates a lever inside the transmission to push a large pin that changes where fluid goes so it will shift down to a lower gear.
• (more advanced) perhaps the governor is dirty and not allowing the shift down? You can take of the tail housing, remove the governor, and clean it up some making sure the pistons move freely. Video link to cleaning and how the governor works: https://vimeo.com/122806383
• (more advanced) shift down/up is caused by fluid pressure in the transmission. Perhaps the pump is worn/old? Maybe the torque converter fins are not catching enough fluid to turn the pump? Maybe some springs broke in the valve body? Honestly, it could be anything. Your last and final option is to rebuild the transmission.

Here's some pics:

(note: you won't see the barbell looking thing on the right bc it's inside the transmission)





Kickdown rod at carb




Kickdown rod at transmission & where it attaches



Where the governor is located in the tail housing

ptharris4990

Braggs, thanks for the quick reply and the pictures!


When I replaced the modulator I didn't notice a pin. There was not one in the old modulator. Would it stay in the barbell/housing piece? If not it may be missing....


I guess I never actually checked the line for vacuum. So I can start there.


I have the kickdown rod adjusted with the screw backed off pretty far so that it only engages at WOT so I don't think that it. Plus at some point it should shift out of first even with it floored right??


Do you know of any videos that show how to remove the governor? I'm only mildly incompetent on the engine side of vehicles but I know virtually nothing on the tranny side. I'm not scared of it, just ignorant.


Also, as a side note, I've read some people suggest revving it out in reverse and while it's floored, ripping through the gears the whole way to first. They alledge it "re-aligns" everything but it sounds like complete BS and a good way to blow something up. Has anyone actually done this this or am I correct in assuming those suggestions were complete junk, if not malicious??

Braggs

The pin is required. If you don't have one, get one. It won't work otherwise.



It won't shift automatically if everything else is not working right. You could try shifting manually until you have time to work on it.


The way the transmission is designed, this shouldn't hurt the transmission. It's gonna be harder on the U-Joints and tires. Don't think of the automatic transmission like gears. All the "gears" are already engaged and until the clutches are compressed will spin freely. You're not trying to shove one set of gear cogs into another when you shift. Instead, what happens is the fluid pressure pushes on a piston that pushes on a set of clutches that makes them stop slipping.

The diagram below shows how the clutch pack works. Transmission fluid pushes the piston (964) against the pressure plate (149) and the steels/clutches (108 & 126) against the front plate (146). The steels (126) have "gears" on the outside of the ring which engage the drum (554). The clutches (108) have gear cogs in the middle of the circle and are engaged with the forward ring gear (592). This forward ring gear is engaged to the output shaft (not pictured) by the forward planetary (582).

So the forward drum is always spinning (because it's got the input shaft stuck in the middle of it) and will only spin the output shaft if the clutches are compressed. All the gears are already engaged and you won't "grind the gears" like in a manual transmission.

ptharris4990

So the tranny has to come out to check the governor?


thanks again for the thorough response!

Braggs

You can remove the tail housing without taking the transmission out of the vehicle. It's just held in by a few bolts.

ptharris4990

Sweet. Looks like my weekend just got planned.

Braggs

Start with the easy stuff first! (Vacuum & pin)

Chris_1

iTrader: (1)

On a side note, if you keep banging a 30 year old truck through the gears at WOT the shifting pattern will be the least of your problems. Just sayin'. Been there done that. As long as you can afford to replace whatever blows up without thinking about it, go ahead.
If having a truck with a blown engine or transmission would present a problem for you, you might want to rethink the right foot position.

ptharris4990

Noted, and me too lol. I blew the head gasket in a Dodge with a 318 and a 727 torqueflite when I was 18 after a guy that raced old mopars tuned it for me.

I don't drive the thing much (just to pick up wood, manure, drywall etc.) and you're right I usually don't have to floor it. My only major issues are when I have to merge on the highway or am stopped at the bottom of a big hill. It's just a pain only being able to shift when the accelerator barely depressed....

To Braggs comments: I checked the vacuum line and it's definitely pulling. I also checked the pin, which does not exist. I fabbed a couple up based on a table I found floating around on this forum but haven't had any luck (if anything the initial attempt made it worse as it wouldn't shift out of first). I noticed the fluid was a little low so I added a qt but I went out this morning to try again with a shorter "pin" about a qt of ATF leaked out. I checked the vac line at the manifold and there wasn't any fluid up there but I as nothing came out initially I was wondering if I should be concerned was it just way lower than I realized.

Any help on the fluid and pin situations is greatly appreciated. Especially the diameter of the pin. I tried using a 14 penny nail and a wire clothe hanger, both were loose in the modulator. Should I go thicker? Also, the spring in the modulator is STIFF to the point that I don't think the vacuum would be able to depress it. Anyone with some guidance on how to set that up???

Also, I got bold last night and tried the the "reverse to first" technique (though not quite ***** to the wall as was suggested). It did not destroy anything but it didn't help anything either.