PRI 2011: ATI Toughens Chrysler TF-904 With New Low Sprag Assembly

When you lose the rear clutch, you essentially lose first gear, and that low sprag assembly is the biggest failure point on the 904 transmissions.

Since it’s inception in 1956, the three-speed 904 Torqueflite transmission has been a versatile mainstay in the Mopar arena and still a popular choice in the drag racing realm. To further the strength and reliability of their TF-904 transmission, which has sports upgraded clutch packs, a Compu-Flow valve body, special low gear sets, and more, ATI Performance Products, has designed a brand new Low Sprag Assembly that features a 1,000 ft-lb element clutch that provides an impressive 800% more contact area that conventional roller clutch.

As you can see on the backside of the case, the all-new sprag assembly is held in place in the case by three 1/4 dowels and four 1/4 shoulder bolts that act as dowels to retain the outer race to the case. This new piece can handle as much as 1,500 ft-lbs, making it exceptionally durable for the even the most powerful of race engines.

According to ATI’s JC Beattie Jr., the rear clutch for the 904’s is it’s “biggest failure point,” and because the loss of the low sprag causes the loss of first gear, it represents a key element in the overall strength of your racing transmission.