Hi everyone. I've followed this forum for some time and finally registered.

I have a 1986 F250 4x4 diesel with an aftermarket Banks turbo and about 80K miles on it. Over the last 5K miles it has developed transmission issue. When cold, it shifts great, but after 30 minutes or so of driving it is extremely difficult to shift into any gear when stopped. I've had several old Internationals with T19 transmissions and 150 - 200K miles and never had a problem like this. I've changed the fluid and checked to make sure the shifter is screwed all the way in and checked the throwout bearing adjustment. I'm kind of out of ideas short of pulling the transmission and taking it apart, so I'm hoping someone on this forum. Thanks in advance.

 

First of all, Welcome to FTE.

Do you have a hydraulic clutch?
Sounds like the clutch isn't releasing completely.

If hydraulic the slave cylinder or clutch mater cylinder is going.
That would explain working cold and not when hot..

If manual linkage,make sure bushings and linkages are ok..

After checking all that, I would guess that the throw-out bearing,pressure plate, or clutch are worn..

Hopefully it is not the tranny.....Hope this helps..

Maybe someone else will join in and give some more advice that is more knowledgeable than I.....Trav...

 

Thanks, I overlooked that. This must be the first vehicle I've owned without a manual clutch. I'll look at the clutch master and slave cylinders next. If it ends up being the transmission i'll put a 5 speed in it.

 

Hopefully, your tranny is ok...Run it till opportunity gives you a deal on a 5speed.

Just my limited experience with Hyd clutches but check fluid level,check for leaks around slave cylinder and master cylinder for clutch...

You may have a little air in the system, just like your brakes, you may have to bleed them....

Also check to make sure that the line going to the slave cylinder isn't too close to your manifolds..(will sometimes boil the fluid)

Hope you get everything going and not have to take a second lien on the house...lol.....Let us know if that is the problem and what you did to fix it...Trav..

 

There have been cases of this in the past, with flexing/cracked firewalls, that worsened with temperature.

It seemed that the firewall was still rigid enough when cold to support the master cylinder OK, but after a longer running period, the engine heat made it more supple & it flexed enough to limit the clutch releasing.

 

hate to revive this thread but also i'm having this exact same issue on my 86 f250. same everything. t19. hard to shift 1st and 2nd when hot.
In the city i don't experience this a lot because im just 20-30 mins away from stuff but when i drive out to the country by about the hour mark in i can't shift to 1st or 2nd at a stop sign without turning the truck off or rolling into 2nd.
I can literally get ready to park it and not be able to get it into 2nd, leave it out of gear, and next day start it and get into 1st and 2nd easy as which is perplexing. No issue shifting in the city, getting into any gears, totally smooth and never hard to find gears til it gets hot.
I replaced the tranny fluid probably 3 years ago but didn't think about what came out of it. just got some 80-90 to put back into it, hoping to change it this weekend and see if it helps at all.

I've driven trucks where the firewall starts to play and its usually pretty obvious feeling like you can press the pedal down til the clutch is depressed and then stomp on it and feel the firewall bending. this does not feel like this issue at all.

 

Like was said in the previous posts, you more than likely have a clutch issue. If you changed the fluid in the transmission, change the fluid in the clutch reservoir. It takes brake fluid. Suck it out with a turkey baster and put new in it and see what happens.

 

I dont thing you can feel a cracked firewall you need someone pressing the clutch pedal and you watch the firewall for movement.
Dave ----

 

I had the identical issue with my 86 F250. I reinforced the firewall around the clutch cylinder and that partially helped but did not eliminate the issue. Then one afternoon I pulled into a gas station and when I depressed the clutch it went to the floor and stayed there. I looked under the truck and the clutch fork was hanging down through a hole in the bell housing and a chunk of the housing was laying on the ground.

I found a used bell housing, cleaned it up and discovered two things, the fork attachment is mounted on a ridiculously thin piece of aluminum, and the used bell housing had small cracks exactly where mine had failed. I took the housing to a welder and he welded the cracks up and added additional reinforcement inside the bell housing around the fork mount. My truck now shifts easier than it ever has.

Crawl under the truck and watch the bell housing metal around the clutch fork mount while someone slowly depresses the clutch and look for movement. As I remember, the mount is in the center of a small rectangular section and the cracks ran around the perimeter of the rectangle.

Good luck.

Edit: Ha! I just realized that this was my original thread and I never posted the resolution. I will say I think I was lucky to find a used bell housing. I found one on Ebay on the other side of the country after the salvage yards in my area had come up with nothing for several weeks. Best to fix the one you have before it fails, if this is the problem.

 

Haha Thanks man! Appreciate the update, I'll check for that -- when i saw a later thread of your bell housing exploded i started worrying about my truck. :P