1949 chevy 3100 rear end questions

[raycow]

If you are going to tear into the engine, most of the procedure is fairly straightforward, but it has a few peculiarities you won't find on modern engines. Before starting disassembly, definitely get yourself a shop manual if you are going to be doing anything more invasive than removing the valve cover.

To get the bellhousing off you must remove the flywheel first. Four of the bellhousing bolts are behind the flywheel. The timing cover is also unusual in that the bottom two bolts go through from the inside. You must remove the oil pan to get to them. It was fairly common practice on teardowns to helicoil the holes in the front main bearing cap and drill out the threads in the cover so the bolts could be re-installed from the outside. This procedure was not authorized by GM, but it saves some work if the timing gears subsequently need servicing.

Probably the oddest thing about the engine is the connecting rod oiling system. The rod journals are not drilled and fed from the mains as in most engines. Instead, the rod cap has a hole in it and a small scoop is attached undeneath. This scoop passes through a kind of tray affair which you wil see when you remove the pan. Be very careful when handling the tray, because it contains nozzles which are supposed to be aimed at the scoops. If the nozzles get bent out of place the oil stream will miss the scoop and the rod bearings will starve for oil. GM used to supply a special tool for aligning the nozzles, but I have no clue where you would find one of those today.

The rods to not have normal bearing inserts, but rather a cast-in-place babbit bearing which is machined to a specified diameter. Final adjustment of the bearing clearance is done with shims between the cap and rod. Aftermarket re-manufactured rods used to be offered which accepted insert type bearings to avoid having to diddle with the shims, but I don't know if those are still available. I believe there are outfits which can still re-babbit the stock rods if you are intent on doing a totally stock resto on the engine.

A lot of people building a driver will replace the 216 with a later 235 which has full-pressure oiling to the rods and no scoops, shims, etc. The 235 is practically a bolt-in, which makes the swap very easy. However, the 216 can provide very dependable transportation if you pay attention to its oddities and do something about the stock gearing.

On passenger cars, the 3.55 gears from a powerglide rear were a bolt-in swap and enabled the car to be driven reliably at highway speeds. Unfortunately, this swap does not work on the AD trucks, so Patrick's (and maybe others) offer 3.55 gears for the stock truck rear. These gears won't work for you because your original torque tube rear has already been replaced. Actually, open drive is really a better option anyway, because it gives you a wider choice of ratios and costs less than the Patrick's gears.

Ray