The Stovebolt Site Forums The Shop Area Driveline Transmission R&R on 1951 1/2 ton

I need to remove and replace the transmission on my 1951 chevy 1/2 ton pickup. I have read the instructions in the shop manual and posts on the forum but I am still alittle reluctant to tackle the job myself. Is there a video out there that I could watch? I understand the enclosed drive shaft disassembly process and the cross member removal but get alittle fuzzy about disconnecting the trans from the clutch housing and the use of the guide pins and the removal of the trans from the inside of the truck. Where do I get guide pins? How do you lift the trans inside the truck? Thank you for your help.

You can make guide pins by cutting the heads of some bolts. The easiest way to lift the transmission is with a floor crane put in the passenger door opening. Use a chain bolt to the top cover bolt holes in transmission, you need to turn the transmission some to get the input shaft to clear the floor coming out.

You didn't say weather it is a 3 speed or a 4 speed. A 3 speed you can remove from under the truck by hand if you are young & fairly strong. It weighs about 75 lbs.

Don,

Thanks for the help. Do you know how long the bolts should be? I will see if I can find a floor crane.

Gary

It is a four speed so it sounds like I will need to find a floor crane.

You can remove it from under the truck. With a good stable Transmission jack with wheels. Remove the shift lever and it will come down and out. You might need to put the truck on jack stands. Or the cherry picker type engine hoist can be used through the door opening. The bolts for the transmission are 1/2 if you pull one of the top two you can get a match for the guide pins. Use the two on top cause the two on the bottom screw in from the bell housing side. Four speed is heavy, so watch fingers and other parts you don't want smashed.

I have slid the SM420 under the truck, then with a cherry picker coming in from the passenger door, I connected my tranny chain (hoist chain bolted to the tranny) to the cherry picker and lifted it right up. Slid it right into place.

If you're dealing with a torque tube, be careful where you put the jack stands. You'll need to support the frame rails in the rear, not the axle tubes This takes the vehicle weight off the rear springs. A friend back in high school was injured when he disconnected a driveline with jack stands under the axle tubes and the torque tube slammed down on him under spring pressure.

I've used a 4X4 wood post across the window openings and a cable come-along to lower heavy transmissions to the ground, and reinstalled them the same way.
Jerry

For your reference and planning the SM420 weighs 135 pounds.

Jerry, I never knew why the torque tube dropped like that I always assumed it was gravity. The way I do it is jack stands under the axle and my floor jack under the torque tube. It holds it in place and I can slowly lower it or I've jacked it up all the way to the floor pan to get it out of the way before.

I have many time done what chadkiser describes (with an SM420 4-speed).

Jack stands placed under the axle housings and a floor jack under the torque-tube to lift the tube up to the floor.

Then put a 2x4 inside the frame-rails so that the torque-tube is held out of the way. Then, the the floor jack can be moved out of the way and be used under the transmission.

Use two transmission bolt "guide pins" as described above. I had to use one upper pin and one lower pin. Two upper guide-pins would not work on my SM420 and clutch housing. So, one upper (longer) pin was screwed into the clutch housing and one lower (shorter) pin was screwed in on the diagonal into the transmission. The lower pin has to short enough to be unscrewed from inside the lower clutch housing.

Just be aware there can be a considerable amount of spring tension on the torque tube and keep it under control. I like the idea of the 2X4 between the frame rails, but having a spring-loaded bludgeon secured with a piece of wood might not be the best idea unless the wood is also C-clamped in place!
Jerry

If it had that much spring tension, I'd also be checking the spring-to-axel pivot bushings.