The Stovebolt Site Forums The Shop Area Driveline 3 SPEED TRANNY ID

My tranny out of my 53 chevy 1/2 ton has it`s case marked 3686832 and also 597676.....CAN ANYONE ID THIS 3 SPEED TRANNY ?

The engine is not original to this truck and is a 235 from a 55 chevy car...the tranny is probably out of a similar car but need to be sure.

The gears are pretty well chewed up and maybe instead of rebuilding, I should buy a rebuilt one like it or maybe something better......What do you all think ??

Probably an SM318. Like this one?

yes...your picture looks exactly like what I have...
A few questions...
#1...are gears readily available for these tranny`s ???
#2....since the gears in my tranny look so bad, am I better trying to find a more updated tranny to replace the old SM318 and if so, what tranny would be a bolt on without modifications if that is even possible ?

A Saginaw full-synchro 3 speed will bolt in and work with the existing clutch setup, but it will require driveshaft length and shift linkage modifications. It's a worthwhile swap in my opinion, as it allows 1st. gear to be engaged without coming to a full stop.
Jerry

I have a '66 Saginaw similar to what Hotrod describes and it is a significant upgrade from a SM318. It required some creative fabrication of the transmission levers/shift rods to make it work with the AD 3 on the tree.

Since you also have an open driveline that is used with the transmission posted by mechanic 58 there are many options. The Saganaw as stated previously, the OD version of what you have which is an SM 319, a T5 and others. There are parts available to repair what you have but it could get costly.
Fred

Parts are available for the 318's...except the 2-3 synchro. You might get lucky and find a NOS one on ebay once in awhile, but they're high as hell. The 318s make a good door stop in your shop or somewhere like that. I agree with HRL and would go with a later model Saginaw. They're cheap and readily available.

My truck has a torque tube driveshaft so the updated Saginaw with syncro would not work as I would also have to convert to an open driveshaft.
Correct ?????
What are the chances of finding a rear end so that I could use an open drive shaft ??????
Either way it looks like I will be spending some big bucks.

Yes, you would have to convert to an open drive shaft style. It's really not that difficult. An 8.5" 10-bolt from a Nova or a Camaro with leaf springs is just the right width. You'll have to cut the perches off and weld new ones on, but it's an easy, cheap swap.

I'm missing something. You identified the open driveline transmission as what you have and then state that you have a closed driveshaft. They are completely different.
Why not find a used stock torque tube transmission, install it and go on down the road. They are advertised on this site all the time and are relatively inexpensive. Many are removed for upgrades and are perfectly useable for stock applications. Why make a bunch of modifications when they are not needed?
Fred

Hi Fred...not sure where you say I identified the tranny I have as an open drive line type transmission ?
I have just taken a closer look at the tranny numbers stamped on the case and they could be ( 591615 ) or they could be ( 597675 )
Is this a ( 318 ) transmission ??? also can these numbers tell what year vehicle it is from ???
Once I know what I have then I can look for a replacement tranny..Your advise to look for a used replacement is the way I am going to go.

Your Trans:
Read This Found right here in River City.

Swap:
If you really do have a 55 motor it's your lucky day. That is the first year that can use almost any transmission. 3 sp, 4 sp, 5 sp and open driveline. Maybe a bell housing change. I would get away from that trans and go open with a four speed truck tranny. I.E. SM420,SM465. Those trannys have a shifter that goes up thru the floor, NO LINKAGE to worry about! You may be able to make the change w/rear end for les than $400 if you find good donor parts and a driveshaft shop and you do all the work.

zoegrant,
I was just responding to information you provided. mechanic58 posted a photo of a transmission that was used on a vehicle with an open driveline.
Your response was "yes..your picture looks exactly like what I have." Then you state later that you have a torque tube.
Perhaps someone can identify your transmission from the numbers, I don't know.
However, If you have an original truck with a torque tube and a 3 speed transmission, it uses the same unit from 1948 through 54.
The transmission mechanic58 posted is not correct for your truck.
The standard 3 speed (open driveshaft) transmission used from 55 through 67 is an SM318. I have seen the previous version (48-54) referred to on this site as an SM318 also.
I cannot confirm or deny that this is correct for your series.
One thing is for certain they do not interchange. The case is different and the internal components are different also.
Fred

rfs56trk, read my post above yours. It indicates he has what they called a Comm. 3 speed. 48-53/4. He could have a "Muncie 318". There seems to be a closed and open model. That could be why he said "looks like that", because it does?

Zoegrant: In 1953 Chevy still called it a "Commercial (truck) 3 speed". The 4 speed option was RPO 318. In 54, same std 3 speed and an optional heavy duty 3 speed RPO 316 and still the RPO 318 4 sp. 55.1 and 55.2 same.
So I guess GM/Muncie was trying to confuse us. A SM318 3 speed and a RPO 318 4 speed? Really? They were synchro in 2nd and 3rd way back when. The first time I see the designation SM (Synchro Mesh) used is in the 55-59 maintenance manual.
None of this matters if you junk it.

Thanks for clearing up (SOME) of my confusion on these 318 trannys.... this is the first truck i have worked on that has a torque tube driveshaft, in fact I had never heard of a torque tube before getting this truck....
I have started to try to find parts for this tranny to rebuild...
I need to obtain a 1st/reverse gear as mine looks fairly worn. The gear has 29 teeth and is 4 1/4" in diameter....I will post in the swap meet...
Here is some info that is casted into the tranny I have.
numbers 591615 GM 3....a tag with rivets states 8 6 1 .....all of this info is on the main body...........on the 4 bolt side cover,numbers 3686832 GM 16. The input shaft has 10 splines......

The Master parts list , group 4.103 shows the 591615 as the transmission case casting number for a 1948-1954 Commercial 3 speed. This appears to be the correct transmission for your truck.

The 3686832 is the cover plate used on all 3 speed transmissions 48-54.

Hope this helps

Thanks for the info on my truck tranny.....a question ...where does one get a master parts list ????

I the 318 was made in both closed and open drive versions - just like the 420. The internal parts are interchangeable with the exception of the tailshaft I would imagine.

You need to use this valuable website to locate part numbers, etc....you will find links to many available on line manuals and I thank Keith Hardy for making this available:
http://chevy.oldcarmanualproject.com/

Another valuable resource is www.gmpartswiki.com - If you have a part number this will help you find out what its used on. It takes some time to do the research, but its a very valuable tool. PM me if you have any questions and I'll try to help if I can.