86 F-350 w/Manual 4 Speed.

In third gear, I can have what feels like an inch of forward/back movement, as measured at the end of the ****, when accelerating/letting off. I don't notice the same issues in 1/2/4, but It is probably there. I replaced the transmission mount, no change. Should I be thinking motor mounts? Is it something else?

I think this movement has screwed a bearing in the tranny, as I now have a "when warm" rattle that goes away when I push the clutch.

I have no expertise/experience in manual cars/trucks, this is my first other than motorcycles.

Any help would be appreciated. Thanks!

 

The gear shift is held in the transmission (shift tower) by a large threaded cap. Search on google (images) for T19 gear shift and you will see it. It may be loose. You may have to lower the rear of the transmission by removing the rear mount or crossmember to access the cap. Or you can access it through the floor board, remove the shifter boot. If it is loose you can tighten it with a large pair of channel lock pliers.

 

That or it's just the normal play between the tip of the shift lever and the shift rails.

 

Thanks for the input. It just seems a bit worrying that, around 15-30 mph, on/off the accelerator can commensurately move the shifter forward/back that much (and I assume tranny/engine/driveline). Like, accelerate....pinned forward...someone pulls out, slam back an inch when I let off the pedal. Take off again and back to pinned forward.

It also seems that better roads are less likely to coincide with this phenomena.

 

I'd say this is one of those many cases where a test drive by a mechanic is worth more than a thousand words on a forum.

 

You didn`t say how many miles on your truck.

You mention a rattle, but goes away when pushing in the clutch peddle.
Could be something in the clutch assy. , when you put pressure on it,
it goes away. Maybe the springs in the pressure plate rattling, throw out
bearing etc...
Not saying you have a clutch problem.

You replaced the trans mount, so that takes it out of the equation. but
there are 2 engine mounts also. Engine and trans sits on 3 rubber mounts,
so you can get some movement with the torque of the engine.

How much movement of the trans stick do you have with the engine off, and
placing it each gear?

I replaced mine a couple years ago with one from PNP out of a 85 6,9. Trans
was nice and tight, so could not let it go to the crusher, along with the Bell Housing
and other treasures.....LOL
I had my clutch replaced by a shop but was having the TO Bearing giving me
problems squeeling and coming apart. Replaced it twice. But had this rumble,
growling sort of low noise. Thinking maybe a bearing in the trans.
So swapped in the PNP trans, and nothing changed.

There was some slop in the original trans shifter, but with around 280K you will
have some.
I was noticing yesterday driving that this PNP trans has almost no noticeable
movement, there is some, but is nice and tight. Has about 190K on it.
My original had 280K.

These are old trucks,lots of rattles and noises, not as tight as when they left
the factory. Lots of rattles and noises, turn up the radio and keep on truckin.

Charlie

 

This ^^^^^^

These four speeds weren't very tight from the factory, and because of the very forgiving characteristics of a high tolerance old school transmission is exactly why they literally go forever...

I drove several years on a bad input shaft bearing, no permanent damage... Third and fourth synchros had been out as well, no biggie it floats pretty well. You can literally hear the synchro on #4 clinking around in there. I was surprised it hadn't broken or something yet but all was well until I tried to do the right thing and swapped it for a junk yard one, then it wouldn't stay in fourth

Mine has quite a bit of shifter play, but our shifters don't use bushings either, it's a loose fit new. If I blip the pedal there's quite a bit of slack in the drivetrain. I'm used to it by now. I don't have a doubt in my mind that it'll still get me home.

Oh and btw, I've noticed that unless you live in a really cold climate, they like regular dino oil better, it's thicker. Mine shifted best with 85-140, I had 80-90 in it (what's specified iirc) and switch to some synthetic 85-140 and it shifted worse. That synthetic 85-140 was thinner than converntial 80-90

Novak sells rebuld kits for $200, all you need is a press, bearing puller, a good set of snap ring pliers, and preferably a torch with a rosebud tip incase any gears don't want to come off. Get em cherry red and they'll slide right off

A person could also order new shift forks and that would probably take some slack out of it, the Novak kit should come with new shift collars, the big round thing the synchros click into, but I'm not sure. The shift fork goes around them and they do wear.

 

Hey all, long time stalker on this site. 1st time posting.
just to throw in my .02...
I drive a 1990 f250 4x4 ext-cab long bed 7.3 idi with a ZF5.
Since I bought the truck it does the same thing in 3rd that the OP mentions. Every other gear is tight and does not do it all all.
But, in 3rd the shifter will move forward and aft without me touching it depending on throttle input.
I always attributed it to a sloppy shift-fork but never really tore into it to investigate because other than that it shifts great and stays into gear.
not sure if it's related but the 3-4 synchro is a little testy and depending on rpm when I'm shifting needs a double-clutch.

 

Thank you for coming out of lurking. I'm going to go with this, as well as the "turn up the radio" option. I've been paying more attention and it really is just third gear. I was trying to make this happen in 2nd and 4th, no dice. Clearly, something isn't perfect. Neither is that old truck.

You all are a great community.