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Discussion Starter #1
89' 164 3.0 with 98k miles and 2 owners

clutch and input shaft bearing were done 1000kms ago-reaction rod/shifter bushings were checked and fine at that time.

Issue is it will grind on the shift down from 5th to 4th...9 out of 10 times it grinds....the only way out is to clutch in and push the lever like you are engaging 3rd and then pull it back into 4th...then it works fine...depending where the revs are you can feather it in but only that 1 out of 10 times.

ive tried feeling my way into 4th but it feels like its caught on the edge...grinding!

It also works fine all the way up to 5th and as above 5th into 4th or 3rd
are perfectly fine.

the box is tight-not sloppy.

Help appreciated thks

Haden
 

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My guess is the tiny safety pawl that goes into the 3/4 shift rod was left out when the trans was taken apart for the new input shaft bearing work. The tiny little rod acts upon the two other safety pawls on either side of it (the 1/2 and 5/Rev rod) by making a connection through the 3/4 shift rod. Something about the movement of the rod toward 3rd that allows the rod to go into 4th (pushes the two other pawls out of the way to allow the shift). Mine was disassembled by a previous mechanic and he forgot this little important piece too. The trans actually locked up into a gear eventually and I had to tear into it and figure out what was wrong. I imagine this is what is wrong with yours too since it is an issue with the 3/4 rod and it is a very small piece that is easy to lose and/or forget. A hard item to source as well, if you need one. Sorry, if this is the case, the trans will have to be disassembled again. The rod I am referring to is about 1.5mm dia. by 1cm or less if I recall correctly. I have a thread with pics on my trans work somewhere on this forum.
Charles
 

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Discussion Starter #4
thks for this

I'll go talk with my guy again and see what parts he had left over on the bench...!

Cheers Haden
 

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Sounds more like bad 7639268 syncro ring on 5th to 4th gear side of 3-4 gear set. If you can't live with problem you will have to pull tranny and disassemble down to to it which means removing 5th gear cover housing, five gears from both drive and driven gear shafts, shaft end bearings, main housing, etc to get to 4th gear gear set.

I had bad one but going the other way from 4th to 5th at high RPMs.

I suggest maybe not using 5th gear or continue the 5 to 3 downshift then to 4 as your are now doing.
 

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I was thinking that too, maybe just don't downshift. There aren't really too many possibilities here, but both involve tearing it back apart unfortunately. If the gearbox operates "tight" I might be inclined to think still that it is a safety pawl missing. The box should operate smoothly between all gears. With the 3/4 pawl rod missing, the box gets more recalcitrant in general because the safety pawls are not moving the way they should to allow the main three shift rods to move smoothly. Their purpose is to prevent multiple shift rods from being selected at once. Do you find the gearbox to operate smoothly in and out of all gears or do you sometimes have to fight with it? I'm no gearbox expert, just observations from having one of these boxes apart. Steve's diagnosis is probably the right one, since he is more experienced than I. I have some gearboxes sitting around if you should need an impossible to get part, I'm sure I can get you one. Let me know.
Charles
 

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Discussion Starter #7
thks Steve and Charles

I spoke with my guy last night-there were no left overs....he also thought the syncro ring on 5th to 4th maybe the issue and suggested as Steve did to "live with it" for now.
The box operarates smoothly-sorry perhaps tight wasn't the term ((tight as in theres no slop like my gtv6!) -will see if I can survive without 5th -thks for your help here.

Haden
 
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