4th Gear Grinding

[CNM67]

The 4speed in my 67 is grinding really bad going into 4th! All the other gears are ok and this problem sprung up outa the blue. Is it the clutch or the trans itself?

[forrestbump]

Probably the clutch. Does your throw out bearing squeal when you're depressing your clutch pedal in?

btw, did you readjust the clutch after you did all the work on your truck? If not, that may be the cause also.

Usually when your clutch starts going out, it doesn't engage or disengage completely...course a clutch that's NOT adjusted will do the same thing.

If your trans was starting to go out, it usually won't stay in gear...doesn't sound like that's your problem though...

[CNM67]

No I haven't adjusted the clutch yet. I need to do that soon. If it it the clutch, Is replacing a clutch difficult?

[forrestbump]

Nope! You'll be glad to have a transmission jack handy...oh yeah, I've got one!

[averagef250]

Probably the clutch. Does your throw out bearing squeal when you're depressing your clutch pedal in?

btw, did you readjust the clutch after you did all the work on your truck? If not, that may be the cause also.

Usually when your clutch starts going out, it doesn't engage or disengage completely...course a clutch that's NOT adjusted will do the same thing.

If your trans was starting to go out, it usually won't stay in gear...doesn't sound like that's your problem though...

When a clutch starts going out it slips.

Not staying in gear is a symptom you will almost never see in a transmission with normal use. You have to abuse the hell out of a transmission to get it to pop out of gear.

Grinding going into gear, as described here, sounds like a bad 4th synchro.

[CNM67]

Probably the clutch. Does your throw out bearing squeal when you're depressing your clutch pedal in?

btw, did you readjust the clutch after you did all the work on your truck? If not, that may be the cause also.

Usually when your clutch starts going out, it doesn't engage or disengage completely...course a clutch that's NOT adjusted will do the same thing.

If your trans was starting to go out, it usually won't stay in gear...doesn't sound like that's your problem though...

When a clutch starts going out it slips.

Not staying in gear is a symptom you will almost never see in a transmission with normal use. You have to abuse the hell out of a transmission to get it to pop out of gear.

Grinding going into gear, as described here, sounds like a bad 4th synchro.

Are you suggesting the trans my possibly need to be rebuilt?

[averagef250]

If I could drive it I could give you an accurate assessment or atleast suggest a route to take for further troubleshooting, but I can't. You have to be very good at communicating exactly what is going on and picking up on any and all changes in the transmissions behavior in order to diagnose something like this through typing.

I'd suggest either doing your best to find an honest transmission shop to test drive it or getting a plan together to tackle the project yourself.

[mmerlinn]

The 4speed in my 67 is grinding really bad going into 4th! All the other gears are ok and this problem sprung up outa the blue. Is it the clutch or the trans itself?

Sprung up out of the blue?

It sounds like your clutch is not fully disengaging. Since this suddenly started happening, it is not normal clutch wear. Neither is it normal sychronizer wear inside the transmission.

I suspect that you have worn out or broken fingers on your pressure plate, a cracked or loose bell housing, a worn out or broken clutch fork, a broken bearing retainer, or a bad throw out bearing. All of those could cause disengagement problems SUDDENLY.

Normal clutch wear and normal synchronizer wear will not cause sudden problems like you describe.

What really bothers me is that this is only a 4th gear problem. If your clutch is not disengaging properly, I would think you would also have problems in other gears. Unless your front input bearing is also bad. But front input bearings never suddenly cause problems. They get noisier and noisier long before they suddenly fly apart. But from your post, it appears that there have been no unusual noises or other problems until now.

Regardless, you will need to remove the transmission to fix any of those problems.

[Madman]

Just my two cents, but if it isn't grinding when you shift into the other gears, I'd say it has something to do with that gear. A clutch adjustment issue should affect all gears, not just forth gear. I'd have to say that I'd start thinking the fourth gear synchro is starting to go bad. Also possible, is there soemthing preventing the shifter arm movement from properly moving when you go into 4th?

[CNM67]

Update. The trans needs to be rebuilt and the shop I took it to wants $1300. So it looks like i'll be searching the web for another T18 in better condition then mine. Thanks for the help though guys.

[cdeal28078]

Do you know how to float the gears? You know getting the engine rpm's and truck speed to the perfect mesh where you can easily pull it out of 3rd and just slip it into fourth with out grinding? Or maybe just a little grind form a tooth or two?
I'd say if it works good in 2nd and 3rd but goes to grinding into 4th then it is the syncros on 4th bad.
I am not a tranny expert so I might be talking pure BS.
I have had a tranny that started grinding in only one gear and it was the syncros. If it grinds in all gears I would think clutch adjustment. Only one gear syncros
clint

[Donnie]

A clutch problem 99% of the time rears it head in all gears. If your problem is related to 4th gear only, as others have suggested.........I'm going with a syncro problem...too
If all was well & it happened SUDDENLY====w/o ANY notice, possibly a broken blocker ring.
Other than the weight, these are easy to work on.......Get a manual & others & myself can walk you thru the repair & tell you where to obtain parts.........Donnie

[CNM67]

I took the 67 to the transmission shop today and the 4th gear syncros and the bearings and seals need repaced.