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86 M/T problem?

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Old 01-18-2018, 04:21 PM
kh0432 kh0432 is offline
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86 M/T problem?

86 F150 302 with 4 speed manual transmission ( 1st is granny gear thats worthless ) First time this has happened to me. Went to downshift from 4th to 3rd
and couldn't find a gear. Grinding like the clutch wasn't engaged. Stopped and shut off engine, was able to put into reverse, started up and everything was fine. Hasn't happened again. Any input?
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Old 01-18-2018, 05:37 PM
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86 F150 302 with 4 speed manual transmission ( 1st is granny gear thats worthless ) First time this has happened to me. Went to downshift from 4th to 3rd
and couldn't find a gear. Grinding like the clutch wasn't engaged. Stopped and shut off engine, was able to put into reverse, started up and everything was fine. Hasn't happened again. Any input?
I would first guess it could be a synchro problem. If you hit the clutch and move the stick right from 4 thru neutral to 3, then the transmission internals will be going at the speed you need in fourth, then slow down in neutral, and then they'll be going way too slow for what third will want. Therefore you need good synchronizers in the transmission to speed the internals up again like a clutch, and get then turning at the right speed for you to complete the shift into third. Otherwise it will grind. Mind you this all is happening while you have the clutch pushed in; the engine speed is not directly involved. If your synchronizer is going bad, you can fix it but you will have to open **** up which is hard and expensive.

What I'd recommend is to double-clutch your downshifts. It will stop the grinding, give you smoother shifts, and preserve the life of your remaining synchronizers. I do it even though my synchonizers work, and it sure helps when it gets cold and it doesn't like to shift.
-- Basically, you push the clutch when you want to shift out of fourth, then let off the clutch while you're in neutral, rev it real quick, push the clutch again, and shift into third. Then release the clutch as usual. The goal is to rev the engine up in neutral to the speed it'll be going in third. With the clutch engaged (foot off the pedal) and tranny in neutral, revving the engine will also speed up the transmission. Basically you will be doing the job of the synchronizers.
If your transmission had no synchronizers or if they were just totally gone, you can do the same thing on upshifts too, just you wouldn't rev it in between gears.

I might have gotten a little carried away describing that. But I have seen a number of older vehicles having downshift grinding problems and double-clutching always helps, and usually completely fixes the problem. The only other reasons it would grind intermittently like that would be if you missed the shift somehow and caught another gear, if your clutch was out of adjustment and decided to act up, or if you have a more catastrophic internal transmission issue (not likely).

Best of luck!
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Old 01-18-2018, 05:44 PM
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With everything warmed up, let it idle in the driveway in neutral, no foot on the clutch. Push in on the clutch and try to put it in reverse. Does it go in a second or two afterward? Or are you grinding and struggling to try to get it in reverse?.
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Old 01-19-2018, 07:43 AM
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Sometimes it grinds a little and if I move the shifter slowly the gears will slow down and go into gear. Other times there's no problem at all. Grinding in reversely happens when it's first started, after it's driven, there's no problem. Maybe I should try pumping the clutch a few times to see if it's a pressure problem with the clutch cylinder and slave?
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Old 01-19-2018, 07:53 AM
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Sometimes it grinds a little and if I move the shifter slowly the gears will slow down and go into gear. Other times there's no problem at all. Grinding in reversely happens when it's first started, after it's driven, there's no problem. Maybe I should try pumping the clutch a few times to see if it's a pressure problem with the clutch cylinder and slave?
If you shift slowly and it works better, that sounds like bad synchronizers. But I forgot that later models have clutch hydraulics. You should first make sure those are working right. You could try jacking up the rear end and blocking the front wheels. Push in the clutch and put it in gear, and make sure the wheels don't start turning. That would indicate that the clutch is engaging a little bit, even when it's fully pushed in.
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Old 01-19-2018, 08:17 AM
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Get someone to push in on the clutch several times, engine off, with the hood up and you are staring at the firewall area above and around the clutch master, which is to the pass side of the brake booster. See if the firewall is moving a lot when the clutch is pushed in. This is a common problem with these trucks,the firewall will crack around the clutch master cylinder, and you will lose clutch action and it can get so bad the clutch master gets cocked and starts leaking inside the firewall.
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Old 01-19-2018, 03:09 PM
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Thanks for all the replies. This morning when I first started the truck, I pumped the clutch pedal about 4 times and it went into reverse without any grinding. Also double clutching helps a lot. I'm leaning towards replacing the cylinder and slave since they look original. BTW, the clutch pressure plate and flywheel were replaced less than 5000 miles ago. i'll check the firewall for flexing but I don't see any cracks. According to my repair manual the original hydraulic parts were sealed and have to be removed as a complete unit. Can the replacement cylinder hose and slave be assembled out of the vehicle and bled before installing?
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Old 01-19-2018, 08:29 PM
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You can bleed them before installing. But get ready, this system gives a lot of trouble when you open it up and have to bleed it. Most of the time you really can't get all the air out right away, and you have to drive it some before all the little bubbles work their way back up the line to the master reservoir. Sort of like burping a baby, the vibration from driving helps work the air backwards up the line.
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Old 01-20-2018, 10:54 PM
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Very simple way to bleed the system
I did this when I installed my ZF.
Remove the clutch maser cylinder, line and slave. (actually quite easy)
Now get a 6' step ladder, Attach the master to the top, and let the slave dangle...
If you have curves in the line, add some weight to the slave so the line has a upward-unobstructed path to the master.
Now fill the master with the slave bleeder cracked, let it fill.
Close the slave bleader, and tap the line starting at the slave and up to the master, you can see the bubbles travel up to the master.
Now slowly pump the master and you'll see more bubbles.
do this until the master can not be pushed in more that a 1/4".
The system is bled!

Mine even has the internal slave, just slide the whole system back into the truck, and only disconnect the slave for install on the shaft and done.
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Old 01-21-2018, 02:10 PM
kh0432 kh0432 is offline
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Finally had someone around to push in clutch while I looked at the firewall and yes. the plate where the clutch cylinder mounts is broken loose. It's only separated at the top left corner looking at the firewall from under the hood. Would it be possible to drill hole there and bolt it back in?
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Old 01-21-2018, 03:03 PM
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You can try to fix it. But there can be more problems there than you realize. Here's a link with some pictures.

https://www.oilburners.net/threads/c...o-part1.44519/

Ford quit making the repair plate, but there is a third party guy that took one of the originals and copied it, and he has a water jet machine and he makes and sells them on the side. Here's his link.

index
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Old 01-21-2018, 03:31 PM
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Thanks, looks like the small reinforcement plate will work since it's only at the top left corner. It's also easier to install. Worst case if it doesn't work i'll go for the large one.
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Old 01-22-2018, 11:49 AM
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Ever since I bought this truck I would always have to push the clutch all the way to the floor to start it. Wound up taking of the safety switch and by passing it. Probably was due to the firewall flexing
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Old 01-22-2018, 04:19 PM
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If you let it go too long, the clutch master will start getting at a bad angle when the clutch is pushed in, and it can start leaking around the rod under the dash.

What aggravates this is increased effort to push the clutch in. This can be caused by the snoot on the front of the trans getting dry. This is the hollow metal piece that the throwout bearing slides back and forth on. It can be difficult to lube though, and not get it on the clutch too.
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Old 01-22-2018, 04:28 PM
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Doesn't deflect much and no signs of fluid leaking which is why I think the small repair will fix it. Guy on ebay has OEM Ford brackets which I ordered. The clutch was replaced by a transmission shop when I first got it and the throw out bearing was also replaced. It's not hard to push the clutch in and I have good movement on the slave cylinder and fork. I'll try this simple fix first and see how it goes.
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