So, I have a 1970 F-100, 2wd, 390 with a T85 3 spd OD tranny. The engine is rebuilt. the tranny seems to shift fine although I have a couple questions for anyone familiar with this combo.
When I drive the truck down the road there is a lot of "play" in the drivetrain somewhere when letting off the gas and when I accelerate again. Like if I am cruising and let off the gas, the truck catches and jerks forward and then back again when I give it gas. There is no smooth transition between backing off the gas and accelerating again if that makes sense.
Also, sometimes, not every time, if I run second gear out a little longer, then when I shift into third gear, it is already in third gear Overdrive. Skipping third gear basically. The electrical circuit works properly to my knowledge.
Any help or thoughts on this is appreciated. Thanks

P.S. I had the rearend jacked up the other day adjusting the brakes and I noticed that the rear wheels spin independently from each other. Like, spinning one wheel doesn't make the other wheel spin in the opposite direction. IDK if that has anything to do with anything. Thanks

Dan

 

Is the electric overdrive switching on all gears? Try disabling the electric overdrive and see if the problem goes away.

As for the rear end it sounds like an open gear meaning only one wheel spins, not a limited slip which is fords version of a posi track.

 

Those OD transmissions had a "coast" built into them. One way sprag that is likely causing you issues. Sounds like OD is engaging without you knowing it, then when you let off the gas it coasts til you override the RPM enough to engage it.

Like mentioned, you need to disable it, pull the cable to lock it out. Then drive it and see how it responds.

These trucks typically have open rearends. If it had a traction lok, they would both spin the same direction. Unless the clutches were worn out and it would then only drive one tire.

 

Since the O/D seems to be engaging by itself, you do not want to pull the cable out while driving, this could cause expensive damage to the O/D unit.

Normally, with the cable all the way in, when you lift your foot off the accelerator pedal at roughly 25 MPH, you will feel the O/D engage.

Once in O/D, if you push the accelerator pedal to the floor, the O/D will automatically disengage aka kick out (acts like a passing gear with A/T).

Letting up on the pedal, the O/D will re-engage, but if you pull the cable out while the O/D is disengaged, it'll now be out of O/D

 

Hey guys, thanks for the replys, I wondered if it was just a "one wheel peel" type rearend hahaha. Anyway. I do understand how do drive the vehicle because it's a Daily driver. The kickdown and everything works correctly. OD works in second and third gear. Also, it doesn't shift into 3rd OD on it's own every time, just sometimes. Usually if I run second gear out further, then it will do it. The coasting feature works properly too, i.e. under 28mph it coasts, and above that when in OD, it has engine drag. So the problem I am talking about just is when the OD is engaged, when letting off and pushing back in the accelerator. If I drive the truck with the cable out (dis-engaged) then no, the problem is gone because it is then a direct drive 3 speed. IDK, it may be normal. I often wonder if it's because I don't have a dashpot on the Holley 600, so the throttle just drops and cuts the acceleration a lot faster. I am going to put one on it anyway.
Dan

 

The only carbs that have a dashpot also have A/T

I've never seen and the Ford parts catalogs do not list a dashpot with M/T

 

Just to add M/T used the trapeze style linkage to take to lurching out that could happen when taking off. If you have a 4V carb and no trapeze set up this could be what you are feeling.

 

Really? I was under the impression that it was the exact oposite of that. That the dashpot is for Manuals and not Automatics. Oh well. You would probably know better than me. I have a factory 4 barrel intake (from an earlier year 390) with a Holley 600. Thanks for the info

Dan

 

AHHH. I didn't know that Brian, but I know what you're talking about. I do not have the trapeze setup. That's odd, Iwonder if it's because of the intake I have. Thanks

 

Just recently there was discussion about throttle linkage in one of these threads here with pictures. I just cant remember which thread.

 

Found it.
http://cimg6.ibsrv.net/gimg/www.ford...039253bdc7.jpg

Posted by HIO Silver

 

Upper pic of linkage: All 2V's. 4V not available until 1974 w/a 390.

If 7A185 is missing, that's not surprising, because its bushings are not replaceable by themselves.

People cannot find replacements, so they have to fab something up.

 

Awesome, I will check that thread out. Thanks Brian.
Yes, 7A185 is missing, that is probably why there is a jenky *** tab on the linkage that I have now, to hit the kickdown switch. Thanks Bill. So, if I locate all of this linkage, will it work on this intake and carb? The intake I believe is from a 65 and earlier FE. Thanks

p.s. 9D709 is missing too, so I guess I have some searching to do!

Dan

 

1958/64 FE intake manifolds have a hole on the right (passenger side) front for the engine oil fill tube.

These engines were only installed in cars, have rounded valve covers without holes in them for smog valve/oil caps.

1965/66 FE engines didn't use the 1967/72 7A185 style of linkage, F100/250 352 2WD's used a 20" long accelerator cable.

There were some 1967/69 & 1970/72 M/T 7A185's (Engine Mounted Shaft & Bracket Assy.) available NOS, but if there's no place to bolt it on, buying one won't do you any good.

 

I was assuming that the OP would pull the cable while stopped. My '64 wagon had this set up and I drove it for about 1/2 year before swapping in a 4spd.