6066 (1960-1966) GMC Truck Club Bitcoin now accepted here! 
Pay Dues
Pay Dues or become a Site Supporter
 



Go Back   6066 (1960-1966) GMC Truck Club > 6066 GMC Truck Club Forum > Transmissions and Rear Ends


Transmissions and Rear Ends Three on the tree or four in the floor? Shift it all here.

Reply
 
Thread Tools
  #1  
Old April 28th, 2020, 02:46 AM
GreenStreak GreenStreak is offline
Junior Member
 
Join Date: Mar 2020
Location: Oxford, Alabama
Truck: 1966 GMC C1000
Posts: 3
Rep Power: 0
GreenStreak is on a distinguished road
Default Transmission Identification + Clutch Replacement

Hey folks,

I'm working on restoring a 1966 GMC C1000 with a 305E which belonged to my late grandfather. One of the things on my list is addressing any issues with the transmission. My family mentioned to me that the clutch needs replacing, which is the reason the truck has sat in a shed since ~2003, but I'm unsure if the clutch actually needs replacing and even what size clutch it takes.

It's a 3 speed manual which was originally a column shifter then converted to a floor shifter to circumvent the supposedly untrustworthy column linkage. I suspect it's a SM318 transmission, but I'm not sure how to verify that. Does anyone know a good way to determine which transmission is in the vehicle? Perhaps a model or serial number scribed onto it?

Secondly, the 65-66 GMC Maintenance Manual says it can be either a 10.5", 11", or 12" clutch. I've found replacement 10", 11", and 12" clutches readily available on RockAuto, LMC truck, etc, but no 10.5". If a 10.5" clutch is the one I need, any ideas where I could pick one up?

I plan to inspect the trans either this upcoming weekend or the next, but I figured I'd ask y'all so I could go into the situation armed with some more informaton.

Thanks for the help!
Reply With Quote
  #2  
Old April 28th, 2020, 09:45 PM
James James is offline
-= Extreme Supporter =-
 
Join Date: Jun 2013
Location: Greer, SC
Truck: 1964 GMC 1500 2wd
Age: 69
Posts: 432
Rep Power: 199
James will become famous soon enoughJames will become famous soon enoughJames will become famous soon enough
Default Re: Transmission Identification + Clutch Replacement

If you have a picture of the transmission, linkage side, would help to identify. There a lot of resourceful folks on this forum to help you with this and any other problems.

Pictures of the truck would also be nice.
Reply With Quote
  #3  
Old April 29th, 2020, 12:15 AM
Quigley's Avatar
Quigley Quigley is offline
Senior Member
 
Join Date: Mar 2013
Location: New Hampton,Iowa
Truck: 1966 1000 Wideside 1962 1500 Wideside 401 Magnum
Posts: 187
Rep Power: 131
Quigley will become famous soon enoughQuigley will become famous soon enough
Default Re: Transmission Identification + Clutch Replacement

If the side cover with the shifting arms is held on to the main transmission with 4 bolts it is a SM318. As far as the clutch is concerned you will know what size it is when you remove it. Hope you have better luck finding a clutch than I did. Ended up having the original rebuilt. Dave
l
Reply With Quote
  #4  
Old April 30th, 2020, 01:54 AM
GreenStreak GreenStreak is offline
Junior Member
 
Join Date: Mar 2020
Location: Oxford, Alabama
Truck: 1966 GMC C1000
Posts: 3
Rep Power: 0
GreenStreak is on a distinguished road
Default Re: Transmission Identification + Clutch Replacement

Thanks for the info! I'll keep that in mind. I plan to do the brakes this weekend, and should have time to take a peek at the trans. I'll take some photos of the linkage, but in the meantime, here's some photos of when I picked the truck up back in March.

https://drive.google.com/open?id=14B...mkt9yrid5mS94n
https://drive.google.com/open?id=144...Nmu3XAt4MF2UAJ
https://drive.google.com/open?id=14D...uybvG4Yprn7H6V

I plan to start a thread under the "Builds and Journals" section to document my progress, just haven't gotten around to it, yet.

I'll update this thread when I get a good feel for the transmission.
Reply With Quote
  #5  
Old May 19th, 2020, 11:27 PM
GreenStreak GreenStreak is offline
Junior Member
 
Join Date: Mar 2020
Location: Oxford, Alabama
Truck: 1966 GMC C1000
Posts: 3
Rep Power: 0
GreenStreak is on a distinguished road
Default Re: Transmission Identification + Clutch Replacement

Updating this for the sake of documentation: finished the brakes and got around to checking out the transmission.

Turns out it's the SM318 that I suspected. Additionally, it looks like the clutch size is a non-issue for now. Opened up the inspection cover and the clutch seemed to have a good amount of life left on it, and the throw out bearing turned smooth as butter. We'll see how well the transmission likes to work when I get to take the truck on a test drive.

Thanks again to Quigley and James.



^(Not sure if above photo will display properly or not, so apologies if it's just a broken mess.)
Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
saginaw transmission identification Pops Transmissions and Rear Ends 9 May 14th, 2015 04:19 AM
Re: 5 speed transmission identification Archiver Previous Forum Posts 0 July 4th, 2010 01:04 AM
5 speed transmission identification Archiver Previous Forum Posts 0 June 30th, 2010 02:09 PM
Transmission Identification Archiver Previous Forum Posts 0 July 30th, 2009 02:46 AM
Re: [6066 GMC] Transmission Identification Archiver Previous Forum Posts 0 July 30th, 2009 01:02 AM


All times are GMT +1. The time now is 12:31 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2013, Jelsoft Enterprises Ltd 681711554703|1710415889|0