69 C20 leaks

[derotoreut]

Just getting used to my new (old) toy. Since getting my 69 C20 I've noticed a couple of issues. Bear with me cause I'm not so familiar with some of these things as many of you.

Looks like rear main is leaking. Probably since it hasn't been run much in last few years. Engine looks like it's been gone over pretty good. No info avail from previous owner. Very clean. New gaskets on oil pan, intake, etc. What are my options here?

Also leaking around speedo cable at TH350 tranny. Looks like it connects into a block that swivels and is further connected into tranny. Should this block be loose?

[derotoreut]

Can anyone out there offer any feed back on my oil leak at back of engine and tranny leak at speedo input? any info would be appreciated.

[Sinister]

Rear main seal needs to be replaced if it's leaking. That thing on your transmission for the speed sounds like an adapter of some sort, not factory.

[derotoreut]

Thanks Sinister. What's involved in rear seal if that's what it is? With bell housing cover removed, it's leaking down on flywheel. Looks like from that vicinity.

[Sinister]

You have to undo motor mounts, raise the motor, put some pieces of 2 x 4 under the motor mounts, drop the pan, remove the oil pump, remove rear bearing cap, replace seal. Watch your distributor and fan when you raise the motor. Might want to remove distributor cap and loosen the fan shroud. It's a pretty big job.

[Deaol]

It is alot of monkeying around, but pretty straight forward, as mentioned above, if your truck can be off the road for more than a weekend i would personally just pull the thing right out.. I did my main not long ago over 3 days, pulled the motor.. and had time to clean up the bay, get some new paint on a few parts and cleaned up some horrible wiring.. also helps to have a extra set of hands.. and maybe a few boxes of beer in the fridge

[derotoreut]

Just don't understand why it would be leaking. Can it be from sitting? Motor has been redone within past couple years. Could be crate motor but not sure. Previous owner had it stored for a couple of years without running it much. He doesn't have much info on it as he bought it out of state from a dealer trade. Then he put it away with the intention of lowering it amongst other things. Looks like work was done well. Very clean, new gaskets, new manifold and carb. Underneath is super clean and all restored with new mounts, etc.

[GASoline71]

Before jerkin' on the engine to change out a rear main... double check your valve cover gaskets. There have been many a valve cover leak that runs down the back of a block and looks like a rear main seal leak. SBC valve covers are the worst design ever...

And yes it can leak from just sitting... seals can get dry, hard, and brittle from sitting.

Gary

[mr48chev]

Yes, I would do as Gasoline 71 said and check the valve cover gaskets and I would check the oil pressure sender or line at the back of the block.
The first thing I do when checking oil leaks is to clean the engine compartment as well as I can to make sure where the leak is actually happening at.

Sinister gave pretty good instructions on changing the rear main seal but complete instructions are also in most repair manuals.

Seals just leak some times and don't really need a lot of reason or cause to do so but sitting and not being driven is probably the hardest thing on seals on any engine except being overheated.

The little box hooked on the speedometer drive is a speedometer calibration/correction device. There are gears inside that can be changed to get the speedometer calibrated if you change gears in the diff or change to different size tires.
You are probably going to have to change the drive gear and the drive gear housing as they tend to wear and cause that leak, or at least that has been my experience.

[GASoline71]

I have that same block on my TH350, and it is kinda "loose". There is only one bolt and a small metal retainer that hold it in place. If I remember right... there is an O-ring seal that goes in there as well. Check that...

Gary

[derotoreut]

Thanks for the advice. I will look into these issues as soon as I can. I'll try to do a little investigating work before pulling the engine for the rear main seal.

Yeah that speedo correction device is kinda weird. It's like a box that swivels on a shaft on one side, with the speedo cable installed on the other side, opposite end. Can't tell if its leaking at the cable connection or where it swivels on the shaft. Looks like it has two screws on each side of it. I'll have to try to open it to take a look.