Swapping Saginaw 3-Speed to a Saginaw 4-Speed - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Canadac10 · 10-02-2019, 01:20 PM

Want to get rid of the 3-on-the-tree and have come across a Saginaw 4-speed.
Nothing crazy with this truck, a mild 350sb. Trans came out of a 6-cylinder camaro, but I have been told it should hold up ok.
My question to anyone with the knowledge. It is a 10-spline. What is the 3-speed? The same? And it also has a 2.84 ratio first gear, narrow ratio trans.
Worth the effort or look else-where?? Thanks for any info before I pull the trigger. Thanks

geezer#99 · 10-02-2019, 01:46 PM

Spline should be the same.
However the input bearing housing size (diameter) might be different.
What year truck?

Canadac10 · 10-02-2019, 04:24 PM

1970. Originally was the straight-6 but previous owner dropped in the 350 and mated it up to the original 3-speed.

geezer#99 · 10-02-2019, 04:44 PM

The index hole is different sized on a truck. Index hole is the big hole that is used to centre the input shaft housing on the bell housing.
Truck index is about 5 inches, car about 4 5/8.
If the sag 4 speed has the smaller housing you’ll need a spacer ring. Otherwise it should bolt up.
Pic in here of the index.

https://www.4speedconversions.com/365_505.html

Here’s the spacer ring you might need.

https://www.advanceadapters.com/prod...-down-to-4686/

Canadac10 · 10-04-2019, 11:22 AM

Thanks for the info!!
Now to pick a shifter...

geezer#99 · 10-04-2019, 12:26 PM

Shifter eh!
A new can of worms.
You might encounter seat interference problems with the shifter you chose. You can buy bench seat shifter handles though.
Another item might be the speedo cable bullet needing a massage to miss the linkage rods.

crazy longhorn · 10-05-2019, 06:06 PM

If you have the original 3 spd (truck) saginaw, remove the front bearing retainer/coller, & bolt it right to the car 4 spd ....its a bolt on

I would reccomend replacing the input shaft bearing at the same time. I do this when ever the trans is out for a clutch, or a swap (good insurance). On the floor shifter, you can get a booma rang (try 5 lever), that should fit your bench seat, that will be a bolt on to the shifter. Check with some of the members, but I think the handle is available from Summit, or JEGS. best of fun, Longhorn

geezer#99 · 10-05-2019, 06:39 PM

Booma rang Mr. Shorthorn!
Is that oz for bench seat shifter.

Good to see you’re still pickin’ and grinnin’!

crazy longhorn · 10-05-2019, 07:31 PM

From one geezer to another....thanks for the pickin & grinnin

I do agree that there will be issues with the speedo bullet/cable. IIRC, it was on the reverse rod. I had to tweek the rod & adjust accordingly. Shorthorn

geezer#99 · 10-05-2019, 08:22 PM

I tried the tweak too but found a ratio adaptor worked better. Dropped it down enough.

10-02-2019, 01:20 PM	#1
Canadac10 Registered User Join Date: Oct 2018 Location: Ontario, Canada Posts: 11	Swapping Saginaw 3-Speed to a Saginaw 4-Speed Want to get rid of the 3-on-the-tree and have come across a Saginaw 4-speed. Nothing crazy with this truck, a mild 350sb. Trans came out of a 6-cylinder camaro, but I have been told it should hold up ok. My question to anyone with the knowledge. It is a 10-spline. What is the 3-speed? The same? And it also has a 2.84 ratio first gear, narrow ratio trans. Worth the effort or look else-where?? Thanks for any info before I pull the trigger. Thanks

10-02-2019, 01:46 PM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,513	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed Spline should be the same. However the input bearing housing size (diameter) might be different. What year truck?

10-02-2019, 04:24 PM	#3
Canadac10 Registered User Join Date: Oct 2018 Location: Ontario, Canada Posts: 11	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed 1970. Originally was the straight-6 but previous owner dropped in the 350 and mated it up to the original 3-speed.

10-02-2019, 04:44 PM	#4
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,513	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed The index hole is different sized on a truck. Index hole is the big hole that is used to centre the input shaft housing on the bell housing. Truck index is about 5 inches, car about 4 5/8. If the sag 4 speed has the smaller housing you’ll need a spacer ring. Otherwise it should bolt up. Pic in here of the index. https://www.4speedconversions.com/365_505.html Here’s the spacer ring you might need. https://www.advanceadapters.com/prod...-down-to-4686/ Last edited by geezer#99; 10-02-2019 at 05:48 PM.

10-04-2019, 11:22 AM	#5
Canadac10 Registered User Join Date: Oct 2018 Location: Ontario, Canada Posts: 11	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed Thanks for the info!! Now to pick a shifter...

10-04-2019, 12:26 PM	#6
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,513	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed Shifter eh! A new can of worms. You might encounter seat interference problems with the shifter you chose. You can buy bench seat shifter handles though. Another item might be the speedo cable bullet needing a massage to miss the linkage rods.

10-05-2019, 06:06 PM	#7
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed If you have the original 3 spd (truck) saginaw, remove the front bearing retainer/coller, & bolt it right to the car 4 spd ....its a bolt on I would reccomend replacing the input shaft bearing at the same time. I do this when ever the trans is out for a clutch, or a swap (good insurance). On the floor shifter, you can get a booma rang (try 5 lever), that should fit your bench seat, that will be a bolt on to the shifter. Check with some of the members, but I think the handle is available from Summit, or JEGS. best of fun, Longhorn __________________ 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....

10-05-2019, 06:39 PM	#8
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,513	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed Booma rang Mr. Shorthorn! Is that oz for bench seat shifter. Good to see you’re still pickin’ and grinnin’!

10-05-2019, 07:31 PM	#9
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed From one geezer to another....thanks for the pickin & grinnin I do agree that there will be issues with the speedo bullet/cable. IIRC, it was on the reverse rod. I had to tweek the rod & adjust accordingly. Shorthorn __________________ 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....

10-05-2019, 08:22 PM	#10
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,513	Re: Swapping Saginaw 3-Speed to a Saginaw 4-Speed I tried the tweak too but found a ratio adaptor worked better. Dropped it down enough.



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