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4 speed with OD

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oregon250 Chris P
Salem, Oregon, USA   USA
I was wondering of any input as to what direction I might look for what might be causing a slight clash i have going into 4th gear. I have the A overdrive. All gears shift good up and down except when upshifting into 4th when not in OD. I get a small clash when not in OD. However, if I shift into 4th from 3rd in OD ( be it a hair on the slow side).....no clash. Since I've got the engine out and apart, might as well look into that trans too.

Thanks Chris

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
My first guess would be wear on the 4th gear synchro ring. 3rd OD is almost the same ratio as 4th direct, and the lockout switch causes the OD to disengage momentarily as the shift rail goes through neutral. I'm guessing that is why you don't get a clash when shifting with the OD switch on.

Normally, 4th gear wears the slowest; but someone may have previously replaced 2nd & 3rd without doing 4th. Or it's possible the ring is broken.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

oregon250 Chris P
Salem, Oregon, USA   USA
Randall, looking at the exploded view of the tranny, I'm guessing the 4th gear syncro ring is the ring closest to the front on the upper shaft. correct? I last had it apart back around 2000. I'll have to check my reciepts and see what I purchased. thanks

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
That's it. Receipt won't tell you which ones though, they are all the same part.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

oregon250 Chris P
Salem, Oregon, USA   USA
Very true..... but it might tell me how many of those 4 I replaced. I'll probably pull it apart in the next couple weeks. thanks

oregon250 Chris P
Salem, Oregon, USA   USA
so I'm ordering some parts for this same transmission (4spd with the "A" OD)........There is a low faint growl like a bearing noise that I notice when cruising in the regular mode but goes silent when in overdrive. Anyone have any ideas if there is a bearing in there that might take the load differently between being in overdrive vs not, and might be responsible for that noise when not in OD? Any thoughts would be appreciated. thanks.

Chris

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Only ones I can think of offhand are the bearing that carries the clutch ring (which takes force in different direction between OD and direct); and the sprag clutch in the tail housing (which only turns in overdrive). The bearings for the planetary gears also change, but they change to not turning in direct drive so I don't think it's one of those.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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oregon250 Chris P
Salem, Oregon, USA   USA
The first one you mentioned Randall, for the clutch ring....might that possibly be the one what the sun gear runs on? It sounds like the sun gear turns in direct and doesn't turn in OD, so if that is the case with the sun gear that would make some sense with that low growl only happening in direct. (possibly part 71 on the Moss blowup). I have only had that OD apart once....and that was close to 20 years ago.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
The sun gear rides on a bushing against the mainshaft. It does turn in direct drive, but at the same speed as the shaft (so the bushing doesn't actually move against the shaft).

The bearing I was talking about is shown (in pieces) on the right in this photo. It goes between the "clutch sliding member" (which I called a ring before, sorry for the confusion) shown in the center of the photo, and the "Clutch thrust ring assembly with pins" shown on the left.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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oregon250 Chris P
Salem, Oregon, USA   USA
Thanks Randall

Work has me out of town. (still waiting for the big R).....Once I get back in town, I'll check that out.
Thanks

johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
If you take the top cover off of the trans, you can rotate the mainshaft and see the 4th gear synchro ring is broken. If it is, you can replace without totally disassembling the trans. Drop the countershaft and remove the input shaft to replace. The new synchro rings are poor quality.

oregon250 Chris P
Salem, Oregon, USA   USA
Yup, that's the one I was looking at in the parts book Randall. So what you're saying is that particular bearing turns only in direct and not in OD?

I hope to get a look at that trans this weekend. I'll pop off the top John and give that syncro ring a look. might be just worn being a small clash and not broke....but i'll replace all 4 rings while apart.

thanks guys

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
That's right, turns only in direct drive. The part on the left above never turns. To shift into OD the clutch in the middle photo gets jammed against the fixed brake ring which stops it turning as well. In direct drive, it is forced the other way, against the annulus that always turns (when the car is moving of course).



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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