'72 C-10 3-Speed to 4-Speed Swap? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

C10 - C90 Bill · 03-27-2011, 08:35 PM

I've got the original 3-Speed Trans in my '72 C-10, which I believe is a Saginaw (looking to verify this), which has a 2.85 1st. The truck has 3.73 Rears and I put extra tall tires on the back to off set the low gear. I'm looking at a 4-Speed Saginaw which has a 3.50 1st. This would give me a much better 1st gear plus an extra gear to boot.

I'm more familair with Muncies, but my question is what do you all think of the 4-Speed Saginaw for an everyday truck? and will it be a direct swap, driveshaft and all?

Any info would be appreciated.

Bill

crazy longhorn · 03-27-2011, 10:03 PM

Use the input bearing retainer from the 3 spd(to give the proper pilot size in the bell), & nut & bolt the bottom 2 ears on the trans.....otherwise its a bolt in. I have run that trans in a couple trucks, no issues on a driver. crazyL

C10 - C90 Bill · 03-27-2011, 10:12 PM

Appreciate the reply.

I just found out that this trans is from a mid-70's Monza. I did a little research in the meantme and someone mentioned it may use the larger driveshaft yoke, something like the TH400 trans yoke. Is that correct? And would there be any other issues being from a Monza?

crazy longhorn · 03-27-2011, 10:41 PM

No, same yolk as your 3spd. You might replace the front bearing before you run it(as a precaution), that is something I do whenever I have the gearbox out. I bet you will like the ratios, its a bit of a stretch from 3rd to 4th, but the rest get you rolling quick ,with a 3.42 or 3.73 gear......crazyL

C10 - C90 Bill · 03-27-2011, 11:29 PM

Glad to hear the yokes are the same. I'd be looking forward to the lower 1st. The 2.85 now is a little rough at times.

Bill

03-27-2011, 08:35 PM	#1
C10 - C90 Bill Registered User Join Date: Nov 2001 Location: Moneta, VA USA Posts: 3,088	'72 C-10 3-Speed to 4-Speed Swap? I've got the original 3-Speed Trans in my '72 C-10, which I believe is a Saginaw (looking to verify this), which has a 2.85 1st. The truck has 3.73 Rears and I put extra tall tires on the back to off set the low gear. I'm looking at a 4-Speed Saginaw which has a 3.50 1st. This would give me a much better 1st gear plus an extra gear to boot. I'm more familair with Muncies, but my question is what do you all think of the 4-Speed Saginaw for an everyday truck? and will it be a direct swap, driveshaft and all? Any info would be appreciated. Bill

03-27-2011, 10:03 PM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Re: '72 C-10 3-Speed to 4-Speed Swap? Use the input bearing retainer from the 3 spd(to give the proper pilot size in the bell), & nut & bolt the bottom 2 ears on the trans.....otherwise its a bolt in. I have run that trans in a couple trucks, no issues on a driver. crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

03-27-2011, 10:12 PM	#3
C10 - C90 Bill Registered User Join Date: Nov 2001 Location: Moneta, VA USA Posts: 3,088	Re: '72 C-10 3-Speed to 4-Speed Swap? Appreciate the reply. I just found out that this trans is from a mid-70's Monza. I did a little research in the meantme and someone mentioned it may use the larger driveshaft yoke, something like the TH400 trans yoke. Is that correct? And would there be any other issues being from a Monza?

03-27-2011, 10:41 PM	#4
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Re: '72 C-10 3-Speed to 4-Speed Swap? No, same yolk as your 3spd. You might replace the front bearing before you run it(as a precaution), that is something I do whenever I have the gearbox out. I bet you will like the ratios, its a bit of a stretch from 3rd to 4th, but the rest get you rolling quick ,with a 3.42 or 3.73 gear......crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... Last edited by crazy longhorn; 03-27-2011 at 10:48 PM. Reason: more info

03-27-2011, 11:29 PM	#5
C10 - C90 Bill Registered User Join Date: Nov 2001 Location: Moneta, VA USA Posts: 3,088	Re: '72 C-10 3-Speed to 4-Speed Swap? Glad to hear the yokes are the same. I'd be looking forward to the lower 1st. The 2.85 now is a little rough at times. Bill Last edited by C10 - C90 Bill; 03-27-2011 at 11:29 PM.



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