3OTT trans identifying - The 1947 - Present Chevrolet & GMC Truck Message Board Network

WB72 · 04-22-2017, 10:35 AM

I'm sure I have a 3 speed Saginaw, how many versions are there? Casting numberson the case are GM 25. 3925647 the 3 may be an 8 or something.

The linkage cover is GM23. 3952645

Tail is GM14. 3873888

Any insight to this assembly? Gear ratios? Age of it?

Not able to upload pics just yet, will add them for clarification shortly.

WB72 · 04-22-2017, 10:55 AM

Here are some pics

weim55 · 04-22-2017, 02:26 PM

I believe the date code shows January 21, 1971. Could possibly be 1981 if it's from a later truck. There are three common versions that I'm aware of:
2:54 1st
2:85 1st (most common in '67-'72s)
3:11 1st
The easiest thing to do to identify the transmission specifically is to take 15 minutes and just pull it out. Count the number of rings on the input shaft if there are any and that will ID it or just put it in first gear on the bench and count the number of turns of the input shaft to one turn of the output shaft.

weim55 · 04-22-2017, 02:34 PM

i'm told there is also a 3.50 1st Version but I've never actually seen one. To ID the transmission by the number of rings on the input shaft :
2.54 = 1 ring
2.85 = no rings
3.11 = 2 rings
3.50 = 3 rings

Steve weim55 Colorado

04-22-2017, 10:35 AM	#1
WB72 Before and After Join Date: Feb 2000 Location: Leduc, Alberta CANADA Posts: 632	3OTT trans identifying I'm sure I have a 3 speed Saginaw, how many versions are there? Casting numberson the case are GM 25. 3925647 the 3 may be an 8 or something. The linkage cover is GM23. 3952645 Tail is GM14. 3873888 Any insight to this assembly? Gear ratios? Age of it? Not able to upload pics just yet, will add them for clarification shortly. __________________ Not Grandpa's C-20 anymore... 383 Stroker 425HP, 485Ft/Lbs Lowered 3.5" Front / 5" Rear 66,000 miles. Alberta, CANADA

04-22-2017, 10:55 AM	#2
WB72 Before and After Join Date: Feb 2000 Location: Leduc, Alberta CANADA Posts: 632	Re: 3OTT trans identifying Here are some pics Attached Images __________________ Not Grandpa's C-20 anymore... 383 Stroker 425HP, 485Ft/Lbs Lowered 3.5" Front / 5" Rear 66,000 miles. Alberta, CANADA

04-22-2017, 02:26 PM	#3
weim55 Registered User Join Date: Jan 2017 Location: Larkspur, Colorado Posts: 916	Re: 3OTT trans identifying I believe the date code shows January 21, 1971. Could possibly be 1981 if it's from a later truck. There are three common versions that I'm aware of: 2:54 1st 2:85 1st (most common in '67-'72s) 3:11 1st The easiest thing to do to identify the transmission specifically is to take 15 minutes and just pull it out. Count the number of rings on the input shaft if there are any and that will ID it or just put it in first gear on the bench and count the number of turns of the input shaft to one turn of the output shaft.

04-22-2017, 02:34 PM	#4
weim55 Registered User Join Date: Jan 2017 Location: Larkspur, Colorado Posts: 916	Re: 3OTT trans identifying i'm told there is also a 3.50 1st Version but I've never actually seen one. To ID the transmission by the number of rings on the input shaft : 2.54 = 1 ring 2.85 = no rings 3.11 = 2 rings 3.50 = 3 rings Steve weim55 Colorado



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