Is it difficult to do??

[MTtruck]

Wanna fix the leak on my 68 GMC 4x4 3/4ton short box with i believe 70-72 running gear. its got a muncie 4 speed and a new process 205 t-case.

[Tx Firefighter]

Tell us what is leaking first.

[MTtruck]

just about a couple drips a day maybe between the tranny and engine. and the occasional drip of the t-case. cant tell were its origin is yet. this truck was unused for years and now after driving it daily it leaks some.

[MTtruck]

Do headers make a big diff in a small block 350 with gas mileage and HP?

[mrein3]

Originally Posted by MTtruck

Do headers make a big diff in a small block 350 with gas mileage and HP?

Yeah. They are a PITA and hurt your power and mileage. That is a pretty big difference for me so I stick with factory ram's horns.

[Dingfodgy]

The leak between the engine and tranny is most likely the rear main seal, which is probably two piece. It's a cheap part and a fairly straight-forward r&r procedure. The leak @ the Transfer Case sounds like a gasket of some sort, but I don't know much about 4x4's, so don't quote me on that.

[D.PASSMORE]

Show a few pictures of the truck and the area of concern... 68 GMC 4x4 3/4ton short box , intresting.

[Longhorn Man]

3/4 ton short bed???

[MTtruck]

mrrein3 are ya sure they decrees performance????????????? i thought it was the other way around....

[MTtruck]

yeah i need to post some pics of this truck. i do think that its a 1/2ton frame with 3/4ton guts. either way pretty cool truck i think, rides like a tank......im also having trouble loading pictures for some reason....really new to this website.

[mrein3]

Originally Posted by MTtruck

Wanna fix the leak on my 68 GMC 4x4 3/4ton short box with i believe 70-72 running gear. its got a muncie 4 speed and a new process 205 t-case.

My 205 case leaks at the speedo output. A LONG time ago somebody posted the part number you use at the GM counter to get the right o-ring for that leak. I never got around to fixing it. I just leave a piece of cardboard under there so my slow drip doesn't leave a mark on the garage floor.

The tranny to transfer case adapter has oil seals on both sides of it. Like the front oil seal on your engine they eventually wear a groove in the sleeve that couples the tranny to the transfer case. The fix is to split them apart, buy a new sleeve and two new oil seals. If that is where it is leaking, and it isn't leaking that bad, I'd put the cardboard on the floor and watch the oil level of both components because those are heavy suckers to be humping in and out on your back.

[MTtruck]

Yeah i do put a drip pan under the truck. like you said, just make sure there is oil and pressure and all is good? much cheaper this way. one day ill fix it. thanks man.

[mrein3]

Originally Posted by MTtruck

Yeah i do put a drip pan under the truck. like you said, just make sure there is oil and pressure and all is good? much cheaper this way. one day ill fix it. thanks man.

I'm not sure what you mean by pressure. The oil in your 4-speed and the oil in your t-case just rolls around in there.

When I had a 3-on-the-tree between my engine and 205 I simply used the same gear oil in both since they were mixing anyways. I'm not sure what the spec is for a 4-speed since I've never owned one. On the few times I drove the truck on those crisp -20 to -30 evenings out to the fish house and back it sure was tough to shift that three speed.

I'm a little more careful with my th350 and NP205 combination. When I bought the used units the t-case was full of a mixture of tranny fluid and gear oil. While I had them on the ground I bought a new adapter which came with seals installed and a new drive sleeve - both were still available over the counter at my local GM garage. So far everything seems to be holding up good. I'm thinking that the first time that unit was installed it lasted 35 years so I should be good for another 30. Which is about how soon I want to install a tranny and transfer case again.

[MTtruck]

oh i just meant engine oil pressure. if that was leaking. This truck supposed to have had a rebuilt tranny and t-case but then again should it leak?? It did sit for a long while after the rebuild so maybe that has something to do with it.