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Lou Jeffery · 01-24-2015, 01:58 PM

I think there may be some confusion with the term sprag. By definition a sprag is a mechanical one way clutch that can be many different configurations. The Turbo 400 built by Hydra Matic used a Borg Warner sprag assy. from 1964-1971. After 1971 it was used only in high performance applications and was replaced by a one way clutch called a roller clutch. Both are adequate for stock applications but the Borg Warner sprag is MUCH more robust.
The Turbo 350 built by Chevrolet and later by Chevrolet and Buick was only built with a roller clutch.
The roller clutch which is much cheaper to produce uses a series of rollers, springs and a cam race. By design the outer race in put in tension and the inner race in compression when force is applied. That said there is an amount of force that will break the outer race at the lube holes. Both the 350 and 400 can easily be converted to the Borg Warner sprag which is a one way clutch comprised of a smooth inner and outer race and a series of segments that wedge to hold one way and freewheel the other. The 400 can be converted using ALL production parts. The 350 requires an after market drum with a modified inner race.
One last thought ALL 4L80E transmissions use the Borg Warner 34 element intermediate sprag assy. which interchanges with the 400.

01-24-2015, 01:58 PM	#2
Lou Jeffery Junior Member Join Date: Nov 2013 Posts: 91 Likes: 0 Liked 0 Times in 0 Posts	Re: Bulletproof TH350 ? I think there may be some confusion with the term sprag. By definition a sprag is a mechanical one way clutch that can be many different configurations. The Turbo 400 built by Hydra Matic used a Borg Warner sprag assy. from 1964-1971. After 1971 it was used only in high performance applications and was replaced by a one way clutch called a roller clutch. Both are adequate for stock applications but the Borg Warner sprag is MUCH more robust. The Turbo 350 built by Chevrolet and later by Chevrolet and Buick was only built with a roller clutch. The roller clutch which is much cheaper to produce uses a series of rollers, springs and a cam race. By design the outer race in put in tension and the inner race in compression when force is applied. That said there is an amount of force that will break the outer race at the lube holes. Both the 350 and 400 can easily be converted to the Borg Warner sprag which is a one way clutch comprised of a smooth inner and outer race and a series of segments that wedge to hold one way and freewheel the other. The 400 can be converted using ALL production parts. The 350 requires an after market drum with a modified inner race. One last thought ALL 4L80E transmissions use the Borg Warner 34 element intermediate sprag assy. which interchanges with the 400.