1968 GMC 3 speed trans - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Jurassic-1** · 02-10-2014, 08:56 PM

I purchased a 1966 C-10 truck. I was wondering if a 1968 3 speed trans has a syncro 1st gear. The 1966 trans does not but I do have a 1968 trans that looks like the same trans. I am not too familiar with these 3 speeds.

**too much stuff** · 02-10-2014, 09:39 PM

If it looks like the same size case, it probably is the same as what you already have. I think 69 is when the synchro first gear was more common. The main case is bigger.

1971 cheburban · 02-10-2014, 10:40 PM

If your lucky you could find what they call the H.D 3 speed, I think they were behind big blocks an heavy duty apps. But they were synchro'd in all forward gears and they may have a little lower first or maybe not, but just get a good shifter for it.

Wrenchbender Ret · 02-11-2014, 11:02 AM

The full syncro came out in 68. Like Stuff says if it looks like the other one it is. The early one had 4 bolts in the side cover. The latter one had 6 or7 & is longer.

19673ontree · 02-11-2014, 12:27 PM

The syncro 3 speeds are long and look like a 4 speed missing the reverse the non sincro 3 speedes are small kinda round looking I don't have a pic handy ,,,

**Jurassic-1** · 02-15-2014, 11:37 AM

Thanks for the info. I will take a closer look at it. I am not sure it will be worth changing if I would need to change a lot.

factorystock · 02-15-2014, 01:38 PM

The manual transmission dept for GM in 60's was not one of the brighter spots. Running the standard 3 speed crash boxes thru 1968 was an imbaressment (Ford had a full synchro in '63). Finding a special option '66 -'68 full synchro is a rareity. All 1969 and newer standard 3 speeds were full synchro. THey will bolt in to your '68 bellhousing, but linkage rods and drive shaft may need to be lengthened or shortened.

02-10-2014, 08:56 PM	#1
Jurassic-1 Registered User Join Date: Jul 2007 Location: New River Arizona Posts: 1,180	1968 GMC 3 speed trans I purchased a 1966 C-10 truck. I was wondering if a 1968 3 speed trans has a syncro 1st gear. The 1966 trans does not but I do have a 1968 trans that looks like the same trans. I am not too familiar with these 3 speeds.

02-10-2014, 09:39 PM	#2
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,817	Re: 1968 GMC 3 speed trans If it looks like the same size case, it probably is the same as what you already have. I think 69 is when the synchro first gear was more common. The main case is bigger. __________________ 67 gmc custom lwb dakota truck. Sold...And bought back 69 swb 4x4 project (in progress) 70 c-10 lwb texas truck 70 4x4/BB/bkts/posi/tach(retired) 70 swb (wifes) 70 jimmy camper 71 K-5 factory 2wd 71 cheyenne 4x4/tach/posi/ plow rig 71 Cheyenne20 BB, buckets, tach, tilt, 4 speed 72 jimmy CST wyoming rig 72 jimmy Colorado rig 72 lifted texas 4x4 3/4 ton burb 65 fury conv. 383/auto 65 chrysler 300 "L" 413 auto

02-10-2014, 10:40 PM	#3
1971 cheburban Registered User Join Date: Jul 2013 Location: Wellsville,ohio Posts: 140	Re: 1968 GMC 3 speed trans If your lucky you could find what they call the H.D 3 speed, I think they were behind big blocks an heavy duty apps. But they were synchro'd in all forward gears and they may have a little lower first or maybe not, but just get a good shifter for it.

02-11-2014, 11:02 AM	#4
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,229	Re: 1968 GMC 3 speed trans The full syncro came out in 68. Like Stuff says if it looks like the other one it is. The early one had 4 bolts in the side cover. The latter one had 6 or7 & is longer.

02-11-2014, 12:27 PM	#5
19673ontree CAN'T FIX NOTHIN Join Date: Sep 2006 Location: SOUTHRUST VIRGINIA !!! Posts: 2,112	Re: 1968 GMC 3 speed trans The syncro 3 speeds are long and look like a 4 speed missing the reverse the non sincro 3 speedes are small kinda round looking I don't have a pic handy ,,, __________________ 1967 C10 Shortbed Fleetside Small back glass 6 cyl 3spd on the tree 3.08 gears underdash AC

02-15-2014, 11:37 AM	#6
Jurassic-1 Registered User Join Date: Jul 2007 Location: New River Arizona Posts: 1,180	Re: 1968 GMC 3 speed trans Thanks for the info. I will take a closer look at it. I am not sure it will be worth changing if I would need to change a lot.

02-15-2014, 01:38 PM	#7
factorystock Registered User Join Date: Feb 2007 Location: west coast Posts: 3,396	Re: 1968 GMC 3 speed trans The manual transmission dept for GM in 60's was not one of the brighter spots. Running the standard 3 speed crash boxes thru 1968 was an imbaressment (Ford had a full synchro in '63). Finding a special option '66 -'68 full synchro is a rareity. All 1969 and newer standard 3 speeds were full synchro. THey will bolt in to your '68 bellhousing, but linkage rods and drive shaft may need to be lengthened or shortened.



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