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Speed Up 1948-1959 GM Pick Up

We often get requests for a formula to make the Advance Design pickups more freeway friendly. Their original ring and pinion gears were created to make the truck’s six cylinder work well with a load and also keep up with the 1950’s traffic on gravel roads and two lane paved highways.

Though a higher speed reproduction ring and pinion was introduced several years ago, some owners still ask for another alternative to get in the “fast lane”. One method has been used successfully for several years and requires most parts from local salvage yards. Obtain the Borg-Warner 5 speed overdrive transmission from an S-10 pickup. It must come from an earlier model with a mechanical speed sensor (on the side of the case). It can not have the more high tech electronic speed sensor as used on the later S-10 pickups with computers.

This transmission will bolt against the original bellhousing of a 1948 and newer (a nice surprise). The clutch shaft which extends out of the front of the transmission is usually too long to allow the ears to bolt flat and secure to the bellhousing face. Therefore, if this occurs, shorten the tip of the shaft about a half inch and all will fit together. This is a must. Otherwise you can even break off a transmission ear when you begin tightening the four attaching bolts.

The ears that attach the transmission to the bellhousing are usually drilled for a metric bolt. They will need to be enlarged for a standard 1/2 inch bolt as is threaded into the bellhousing.

The V-8 Camaro 5 speed transmission is also similar to the S-10. It is said to not be as low geared and this makes it more desirable. The Camaro shift lever is too far back for the 1948-59 pickup. The bench seat is in the way. To correct this, use the S-10 tail shaft housing and case top cover. This will allow the vertical lever to come through the original floor in the correct position.

The input shaft of the 5 speed will have either 14 or 26 splines. Therefore, the clutch disc must match the transmission and not the 10 splines from the original 1948-1959 truck.

The attractive S-10 boot is still available from GM and the shift knob of choice is from a late model 5-speed Jeep. It screws on perfectly and looks great! The S-10 shifter clears the seat cushion and looks like it was installed by GM.

The next step is the differential. An open drive shaft style will be necessary to match up with the 5-speed but this is a subject for an totally different technical article.

The result of this change is lower RPM’s and speed to keep up with traffic flow on most modern highways.

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