J20 Transmission questions?

[Werndogz]

It may be a dumb question but what manual transmission is in a 1979 J20? Also my truck will only go into gear if I turn off the engine, anyone have any idea why? I was thinking the clutch or slave cylinder aren't adjusted right, also the fluid was really low. Any help would be great.

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[tgreese]

'79 J20 has mechanical clutch linkage, not hydraulic. Suggest you post a picture of what you are looking at.

The '79 TSM is online free to read and download. https://oljeep.com/

TSM.png

Both manual transmissions - T-15 and T-18 - are shown here, plus the clutch linkage.

[rocklaurence]

Most likely a clutch/linkage failure or adjustment is needed.

[Werndogz]

I adjusted the linkage both ways and still won't go into 1st gear with engine running, I ordered a new clutch. Hope this fixes the issue.

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[devildog80]

So you really did not actually diagnose the problem, to know exactly what you need? This can get very pricey just throwing parts at it. Is another FSJ Forum Member close, perhaps stop by to help diagnose correctly?
As asked above, can you get us some pics?
Have you pulled the bell housing inspection plate yet? Get some pics in there too, linkage, engine bay with linkage showing.
What transmission do you have? You need to know for sure, as it could be a shifter stick issue, transmission, clutch.....
What changed between the time it was driving fine, but now has a problem?
Someone else drove it last?
Lots of questions we need information to help you best.

[Werndogz]

Yes a friend drove it last before it started slipping out of 4th gear. I'll grab some pics but not sure how to attach them.

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[Werndogz]

What is the bell housing inspection plate?


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[Werndogz]

And I'm pretty sure it's the Borg Warner t18 transmission

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[Werndogz]

Dumbest thing ever, I just took out the shift lever, cleaned everything up and put it back in and now everything works just fine. I still think I have a 4th gear synchro going bad though.

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[Werndogz]

Here are some pics since you were asking

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[seventynine]

If it has four forward gears and is stock it’s a T-18a Trans. First gear is an un-synchronized granny low (6.32:1) pretty much unusable on the street. Sounds like synchronizer issues or a clutch problem if it is happening in all gears. I had a few and sometimes I have to feather the clutch and throttle a bit to get it into gear. These do not shift quick…you can eat lunch between shifts

[Werndogz]

New problem....
So it started doing it again where I couldn't get into any gears unless the engine was off so I repeated what I did yesterday by pulling out the shift lever and put it back in. Now I'm stuck in first gear only and can't get it out.

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[tgreese]

Make sure the forks are lined up with their grooves in the shift collars. Put the transmission in neutral by moving the collars before you set the shift top on. Put the shift top in neutral and watch that the forks go into their collars. Should drop straight down if you have the transmission and the shift top in neutral.

A problem with the 4th gear blocking ring or synchro hub seems quite unlikely. The synchros act like clutches to speed up or slow down the gears as they mesh. Top gear typically sustains the least wear of any of the forward gears. You would almost never shift up to top gear at a high engine speed, and you never downshift into fourth... very little stress.

[Werndogz]

Can you call me, 660-624-9475

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[Werndogz]

Also, when I start the truck with it in first gear and clutch fully depressed it moves forward slowly as if the clutch is slightly engaged. Then when I pull it out of gear it won't go back in to any gear unless the engine is off.

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[devildog80]

If the truck is moving with clutch depressed, sounds like adjustment is needed, as pedal should only have about an inch of play before engaging the fork to throwout bearing. So I would think, as you describe your situation, you have much more pedal travel before that happens?

[Werndogz]

Not at all, my pedal is very stiff and I have adjusted it so that clutch disengages at about 1/4 of the pedal travel

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[devildog80]

What is the distance the pedal goes from no engagement as you would be driving, put your foot on it and push, and it contacts the throwout bearing?

[Werndogz]

About an inch or two, maybe slightly less. But even when I have it adjusted the other way so throw out bearing is engaged closer to the floor I still have the same issues.

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