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junkmandan3 · 07-21-2015, 12:04 PM

"Working fourth" or short 4th five speeds are GM's answer to take advantage of the ratio split in a 2 speed axle that enables you to keep the RPM split in the top 4 gears even . In the case of my 4-53T in my pickup it works out to a 300 RPM split instead of 500, utilizing the 27% split in the auxilliary which is similar to the split of a 2 speed axle . I believe GM collaborated with Spicer to design the ratios which is about 17% in 4th gear.

07-21-2015, 12:04 PM	#21
junkmandan3 Registered User Join Date: Dec 2013 Location: Northfield,Ohio Posts: 221	Re: when is a 5 x 4 not a 5 x 4 ? "Working fourth" or short 4th five speeds are GM's answer to take advantage of the ratio split in a 2 speed axle that enables you to keep the RPM split in the top 4 gears even . In the case of my 4-53T in my pickup it works out to a 300 RPM split instead of 500, utilizing the 27% split in the auxilliary which is similar to the split of a 2 speed axle . I believe GM collaborated with Spicer to design the ratios which is about 17% in 4th gear.