60 C10 3 Spped 1st Gear Downshif Scrubs HELP

[tuskiso]

Hi all,

My 69 C10 (3 speed manual transmission, shifter on the floor/ converted from three on the tree) scrubs when down shifting from 2nd back to 1st gear. The transmission appears to be an original for the 69 C10. The gears also hang from 1st to 2nd frequently. My greatest problem is that I can't down shift to 1st without coming to a stop (if I don't stop, it takes a while and there is a lot of scrubbing).

I recently had both the clutch and flywheel replaced. Is this problem an indication that the transmission needs to be rebuilt. I'm considering a RESTORE of this truck (since the numbers appear to be matching) and I want to keep the original transmission.

So my question is: (1) What would cause this problem ? (2) What action would be required to fix it.

Thanks for your assistance in advance.

[19673ontree]

If you will take a pic of the transmission and post it we can tell you for sure but dont sound to me like anything is wrong ,,,,,
#1 you say it is srubbing grinding ? When going from second back to first without stopping that sounds like a normal non syncronized 3spd
#2 gears hang up when shifting from first to second ,,,, sounds like driver habbit just need a little practice ,,,
Most everybody hates the 3 on the tree shifter they say they hang up ? I have drove these trucks with the 3 on the tree since about 1984 and never had a problem my 67 I have now shifts great for me but if anybody else drives it the gears hang up ? Ive been told the shifter is tore up ? Is it ? lol
Anyway post a pic of the transmission I bet its a good ole non syncro 3spd ,,,

[Prescott]

clutch linkage adjustment may be needed. this could solve both problems

[19673ontree]

Originally Posted by Prescott

clutch linkage adjustment may be needed. this could solve both problems

If it has the original non syncro 3spd in it you have to stop to go from 2nd to 1st nothinig will change that , he says its hanging up shifting from 1st to 2nd so I'm assuming it shifts from 2nd to 3rd ok which means clutch is fine ,

[geezer#99]

You're right 67!
Double clutching will get you back to first But most people can't figure that out. Also shifting 3ott people don't understand it's a lazy 'H' pattern and not a straight line speed shifter.
If it's hanging up on his 1 to 2 shift it's his shifter needs adjusting.

[tuskiso]

Here are a couple from the video of the clutch/flywheel replacement.

[tuskiso]

If this is a non synchronous transmission, is it possible to rebuild as a synchronous transmission while retaining the original housing.....?

[19673ontree]

That's a saginaw syncro 3spd it ust have bad syncos in it ? If it does I bet its got 2 or 3 mmillion mmiles on it LOL

[tuskiso]

What's a good guestimate on a rebuild.....?

Also, since I want to restore the truck, what other things should I consider doing to this transmission while getting it rebuilt (to maintain original parts, but improve driving experience)

Thanks for your assistance in advance

[tuskiso]

Originally Posted by 19673ontree

That's a saginaw syncro 3spd it ust have bad syncos in it ? If it does I bet its got 2 or 3 mmillion mmiles on it LOL

Almost forgot..... don't know how many miles it has, the Speedometer/Odometer was broke when I got it. Have replaced the cable and added a 90 degree cable adapter (speedo connector sets right by the shifter linkage after conversion to floor) But the 250 CID 6 cylinder engine appears to run very well. It has quite a bit of Git-Up-N-Go. Working on Fuel gauge now (sender unit not working or wire to it is broke, got to figure out how to remove bench seats to get to tank)

[whiskey_marc]

1st gear is most likely a "granny" gear. As far as I know that gear is not synchronized. Therefore, it is not meant to be used as "First" unless you are towing something.
That is why the gear grinds when you downshift into it. My 4 speed Saginaw is the same way. Start in second gear.

A rebuild is nice, but you will have the same problem after

[geezer#99]

Originally Posted by whiskey_marc

1st gear is most likely a "granny" gear. As far as I know that gear is not synchronized. Therefore, it is not meant to be used as "First" unless you are towing something.
That is why the gear grinds when you downshift into it. My 4 speed Saginaw is the same way. Start in second gear.

A rebuild is nice, but you will have the same problem after

JFYI whiskey marc that's possibly a full synchro 3 speed with a 3 to 1 first gear. Not a granny 4 speed that has a non-synchro 6.43 to 1 first gear. Different tranny.
It grinds because of bad synchros and rebuilding it will fix it.
Easiest way to spot a full synchro from a non synchro first tranny is the number of bolts holding the side cover on. 7 bolts for the full synchro, 4 bolts for the non-synchro.
And for the op you can't make your non synchro tranny a full synchro type. Not enough room inside the case.

[tuskiso]

Originally Posted by geezer#99

JFYI
Easiest way to spot a full synchro from a non synchro first tranny is the number of bolts holding the side cover on. 7 bolts for the full synchro, 4 bolts for the non-synchro.
And for the op you can't make your non synchro tranny a full synchro type. Not enough room inside the case.

Here is another pix of the tranny while it was on the lift. I have marked the 4 visible bolts. Most likely 3 or 4 more not shown on the front upper quadrant that's not visible.

[19673ontree]

So now with pictures and we know it is a syncro transmission all you need is to take the transmission out and either have it rebuilt or I will bet you can find a good one cheap ive got like 4 of them I think the saginaw 3spd is a great transmission they last and last I bet yours just needs new syncros bearings and seals I bett all the gears are good ,,,,,, I have no idea how much it would cost ? Personally id just get another one you can swap that out in an hour ,,,,

[19673ontree]

Originally Posted by whiskey_marc

1st gear is most likely a "granny" gear. As far as I know that gear is not synchronized. Therefore, it is not meant to be used as "First" unless you are towing something.
That is why the gear grinds when you downshift into it. My 4 speed Saginaw is the same way. Start in second gear.

A rebuild is nice, but you will have the same problem after

A full syncro saginaw 3spd in good shape will downshift from 2nd to 1st moving ? 20mph or so with no grinding ,