Want to install a 5 speed with OD transmission while keeping your original clutch, flywheel, and starter?

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Change out the input shaft?

This tip details how to install a T5 transmission while retaining original flywheel, clutch assembly and starter.

I recently obtained a T5 (transmission number 1352-145) with a 14 spline input shaft. The 1352-145 T5 gear ratios are 1st 3.76 2nd 2.18 3rd 1.42 4th 1.00 5th .072. They are out of an 1985 / 1986 L4 or V6 Chevy S10 PU. Transmissions of this vintage used mechanical speedometer. Later models may use an electronic sensor.

Don't get confused on the transmission's I.D. There are numbers all over the casings that are just part numbers. Look for the white and green sticker on the main case or the metal I.D. tag bolted to the tail shaft housing. The metal tag is about three inches long and about a half inch wide. The identification tag is a white and green sticker with numbers on top of the main case.

I found that the easiest way to solve the problem is change the input shaft (14 spline to a 10 spline).

You have to remove the old 14 spline input shaft to make sure you get the right 10 spline replacement shaft (the gear ratio on the inside will differ). Obtain a 10 spline input shaft (I used a Jeep input shaft factory part No.1351085008). This spline has a 21 tooth gear and the spline is one inch in diameter, just like the early originals. I had a machinist mill off a half inch of the pilot shaft and then put a slight chamfer on the edge to aid the insertion into the pilot bearing like the original. You will have to press on a new bearing (part number K-5) if you purchase a new one. I recommend a new one -- it saves a ton of time. The housing seal part number is 100254.

Drill out the metric transmission mounting holes to fit the 1/2 inch standard ones on the bell housing.

Now you can use the original clutch, throw out bearing, pressure plate, starter and flywheel. The key is to use a SM420 bell housing (from a truck with the foot pedal starter if so equipped).

I did this on my 1951 Chevrolet coupe and it works awesome. I was lucky that my brother had purchased a 1955 Chevrolet First Series 1/2-ton truck. He pulled the six out and installed a V8. I had sense enough to keep all the parts except the foot pedal. I used everything and installed it on my 1955 261 engine that was pulled out of a school bus.

The coupe turns 2000 rpm's at 66 mph with a 3:42 rear end and a 0.72 OD fifth gear.

This method will let you use the original flywheel, and clutch setup on most any early year truck or car. It takes the guess work out of it. Of course, your driveshaft and crossmember will also need to be modified depending on your year and model.

My friend owns a transmission shop and he was amazed how everything turned out. He charged me $75 for the input shaft and another friend used a ceramic cutter to mill off the end (the shafts are hardened). I owe my machinist buddy a beer now (It pays to network and make friends)! Something tells me though, it might be a rough night in the garage.

My friends at Moline Transmission Service (309-762-0221 - Moline, IL.61265 ) performed the rebuild and obtained my parts. Ask for Tony if you have any questions on the subject; he is a wealth of knowledge and very willing to help.

I recommend you have a local machine shop to mill off the input shaft with a ceramic cutter.

Steve

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