3 speed syncro trans

[rlb67]

Hi all,

I'm new to this site and have a question about a 3 speed transmission. I have a 67, 250, 3 speed on the column. I assume that I have a non-syncronized trans (low gear only). I was wandering if anyone knows if I can get a kit to make it syncroized or will I have to go with a later model transmission? If I have to get a later model, what model do I need to look for that will be the least amount of modifactions or none at all? Any help will be greatly appreciated.

Thanks,

[Botietruck]

I'm not an expert in transmissions, but I thought the non-syncros went out in the early 60's. The side cover on a fully synco looks like this. The older non syncro transmissions had a 4 bolt side cover, much shorter than this one in the pic. This is a 3 spd. Saginaw with the overdrive unit. Someone else might be able to add some more accurate info.

[rlb67]

Maybe my blocking ring in low gear is just wore out. I will check the bolts tomorrow.

Thanks for input,

[dan42]

Should be a synchro. My '67 had a three speed with the 327. The only non-sink was the SM420 at the time, as far as I know.

[rlb67]

How do you identify a SM420?

[northerngmc]

Have you tried adjusting the 3 speed column?

May seem silly but I drove a truck for 10+ years thinking that I did not have 1st gear syncro, then a buddy adjusted it, and man does it shift nice now.

Take a look at this thread in the FAQ section http://67-72chevytrucks.com/vboard/s...d.php?t=215307
It has great pictures and this guy had adjusted it out of the truck, but it is a simple adjustment to do in the truck, takes about 15 mins. I would start with the adjustment.

Good luck, cool truck and welcome from the far north.

[samwise68]

an SM420 is a 4 speed granny gear tranny, with reverse towards the driver and down.

if you have a 3 on the tree, then you don't have a SM420.

i'd check the linkage as well..they can be a real PITA at times, but when they're smooth...ooooo man. are they nice.

-Sam.

[rlb67]

That may be it. I will adjust the column this weekend. Great article on how adjust column.

Thanks for the info,

[Brad]

It's a '67 guys. It probably does have the non-synchro 1st Muncie transmission. No amount of adjusting will fix that. You'll need to go with a Saginaw 3 speed. Plenty of them around and you'll just need to shorten your driveshaft.

[rlb67]

What model truck do I need to look for with the Saginaw trans?

[Brad]

Just a WAG but '68 and up???

[70GMCer]

My 70 had a Sag 3spd in it. Fully sync. Then went to an auto.....

[crazy longhorn]

Originally Posted by Brad

Just a WAG but '68 and up???

Yup! Just 1 other problem....the 67 truck has a 4 11/16 centerhole in the bell, where 68 -on truck bell is 5 1/8". You can plug a saginaw (car) 3 or 4spd right into the 67 bell, (also Muncie 4 spd ) M20/21, or swap the front bearing retainer/throwout collar from the car to truck trans(saginaw only). The collar you have on your little 4 bolt Muncie will not work on the saginaw. Note that if you use the car trans, you will need to nut & bolt the bottom 2 holes (trans to bell), as the car bells had all 4 mount holes in the bell threaded, & the truck has the top 2 threaded, with the threads in the trans ears @ the bottom. crazyL

[Brad]

I forgot about that. I remember that I did this swap a year before going to the 5 speed and had 2 bellhousings to choose from.

You know what- your bellhousing is the correct size for the T-5. Why don't you find a Camaro T-5 from a V8 car and it'll virtually bolt right up to your current bellhousing? In fact mine did when I forgot to enlarge the 4 mounting holes. You'll have 3 more gears to choose from and I guarantee you that you'll be much happier. It may sound intimidating if you've never done it before but I can say with confidence that it's as simple as drilling the 4 mounting holes to 1/2", bolting it up, punching a hole in the floor for your shift to poke through, and shortening your driveshaft. Seriously, it's that easy. The only potential problem is that the Camaro trans shifter sits where a bench seat goes so you'd have to create a shifter rod (much like a Hurst Tri-5 shifter) or go with bucket seats (also some have converted to the S-10 tailshaft). I've posted on hear before and can guide you along if needed. I've done this several times.

Btw, save your 3spd column linkage if you go that route because every once in a while somebody here wants to convert back to all original linkage.

[68gmsee]

My stock 68 GMC 250 six had a non synchro transmission on it. I converted it to a synchronized Saginaw many years ago. Don't even remember where I got the trans from but I believe it came off a Chevy V8 truck.

[larry may]

Originally Posted by rlb67

Hi all,

I'm new to this site and have a question about a 3 speed transmission. I have a 67, 250, 3 speed on the column. I assume that I have a non-syncronized trans (low gear only). I was wandering if anyone knows if I can get a kit to make it syncroized or will I have to go with a later model transmission? If I have to get a later model, what model do I need to look for that will be the least amount of modifactions or none at all? Any help will be greatly appreciated.

Thanks,

Here is some help for you. You pay the shipping I have one I'll give you. Gotta be a board supporter first though........

[crazy longhorn]

Originally Posted by 68gmsee

My stock 68 GMC 250 six had a non synchro transmission on it. I converted it to a synchronized Saginaw many years ago. Don't even remember where I got the trans from but I believe it came off a Chevy V8 truck.

Yea, it may have been 69 when the 6 /3spd trucks came with the saginaw as standard equipment...crazyL

[factorystock]

There was a change in Saginaw Muncie transmissions I believe in 1968. The 4 speed SM420 was replaced with the SM465 and the 3 speed non synchro SM318 was replaced with a syncro SM326. The input shaft size was increased, so bellhousing and clutch needs to be changed also?

[rlb67]

Thanks for all the info.

[crazy longhorn]

Originally Posted by factorystock

There was a change in Saginaw Muncie transmissions I believe in 1968. The 4 speed SM420 was replaced with the SM465 and the 3 speed non synchro SM318 was replaced with a syncro SM326. The input shaft size was increased, so bellhousing and clutch needs to be changed also?

You can use the same clutch(1 1/8"-10 spline).....68 did change the center hole in the bell, that the input bearing retainer pilots on. crazyL