The Stovebolt Site Forums The Parking Lot Big Bolts Oil in vacuum lines

In a recent post I talked about replacing the 2 speed selector valve on my 48 Loadmaster 2 ton but have not had any luck finding a replacement. I decided to clean up the one I have and use it. My question is should I have oil in the lines going to the 2 speed unit on the rear? Also on another post I saw a breakdown of the 2 speed unit and noticed it has an inner seal to I think prevent this. Does anyone know of a source for this seal and possibly the diaphragm seal as well? If I cant find these items will the oil hurt anything? It will only be sucked into the intake be burned up?

Thanks, JMH

is it oil or is it brake fluid. where in the lines is the oil you talk about. how much oil are you talking about

The oil is in the lines that connect the chassis mounted valve and the 2 speed "pancake "located on the rear axle. I am not sure how much but I think it is probably too much.

JMH

i would pull the flexible hose that goes to the manifold just to see what comes out of it. if theres oil there, i would pull the vac line off the bottom of the hydravac and see what comes out of there. if nothing comes out of line at the hydravac which is good then i would be real puzzled on where the liquid came from.

If you take the size of seal to NAPA or such parts house they can get them for you.
I just got some for a 54 chevy 6400 in that way.

oasisfarmsinc

Sir,

Are you talking about the seal inside the pancake located on the rear housing? The parts breakdown shows one seal that separates the lube oil in the rear and the diaphragm.

JMH

JMH,
My COE has a 2 speed rear axle also, and when I took everything apart, I had oil in my vacuum lines, too. My diaphragm was intact, so the oil was in the line that attaches to the inboard side of the diaphragm. The gear lube was getting past the worn seal that is in the shift cover. My seal had a number and I just took it to a truck parts place and they found me one. So, if you pull the flexible rubber lines that go from the steel vacuum lines at the rear to the shift cover (or pancake as you call it), you should find the source to your oil.

The other line was clean, because the diaphragm would have to be perforated for gear oil to get to the outboard side. I used to have a parts number for the rubber diaphragm itself, but can't locate it right now. You should be able to find the part number in the Old Chevy Manual web site. At the valve switch at the front of the truck, there was oil in all three lines,as the oil had crossed over from the switch. I don't think ultimately the oil itself would hurt anything, other than possibly lead to sluggish shifting from a vacuum leak back through the differential. You might get exhaust smoke if the oil made it to the intake manifold which would eventually happen if there was enough oil.

I only have a rolling chassis now, so it will be awhile before I start up the truck and see if I fixed the leak.

Good luck!
Kent

after looking in the maintenance manual i can now see how gear oil can get into the lines. maybe there is nothing wrong with your selector valve since the problem seems to be at the rear of the truck.

Wrench Fetcher,
After some thought you described my situation exactly.The oil could only be coming from the seal described.I will remove said items and do an inspection. I also plan to replace the old copper lines with air brake line and new fittings.If I should need the (pancake) seal do you have a source.

Thanks,
JMH

JMH,
You should be able to get the seal at any good parts place. If you remove it and take it with you, they will either find the number on it or pull out their calipers and find one for you. Don't go to a place that just has had kid with a computer, as he won' be able to help you, most likely.

For the diaphragm itself, once I located the part number, I simply called my local Chevy dealer parts department. When I gave them the number they came back with "that is an obsolete part, but let's look in our parts locator computer" A couple of minutes he came back on and said a GMC truck place in Phoenix had one, and sure enough, they did. I tried them again, when going over the differential itself, I found severely chipped spider gears. They, of course, didn't have them, but gave me several locations around the country that did. I was able to locate the gears and the corresponding thrust washers, as well. It is pretty cool when you are looking for 60 year old parts and someone went to the trouble to enter old stock into a national data base.

Wrenchfetcher,

Thanks for the info. Can you supply me with a part no. for the diaphragm? If not can you give me the name of the Chevy dealer where you purchased it. My local dealer just laughed when asked for his help.When I removed mine I found the source of the oil. My diaphragm was toast.If I can't find one can anyone tell me of another fix. Maybe a mechanical linkage of some sort?

Desperate I am,
JMH

JMH,
You can't just call a Chevy dealer. They have no way to look it up. You need the part number and then ask for them to use their parts locator computer. Then they will just tell you whether they have a listing, but won't know what kind of part it is. I called Chapman Chevy in Tempe, Az (480.838.1234 and ask for the parts dept.). They have helped me twice but didn't sell me the part, just gave me the number to call where their computer indicated the place had what I was looking for.

Using the http://chevy.oldcarmanualproject.com site I believe I found the part number 3847058. It is group number 5.635. Look on pg. 504 in the 1929-1957 Master Parts List and Accessories. If you can wait, next week I will be up at my shop, 120 miles away from here, and will check to see if I still have the box my new diaphragm came in. If I do it will have the part number on it (maybe).

If this doesn't work let me know as I have a contact where you can call and see if they, by chance, have the part.

Since your diaphragm is toast, you should have a major vacuum leak, regardless of whether you selector is in high or low range. If your truck is running, you need to block off both hoses at the back end until you solve your problem.

Isn't this fun? Working on these old beasts can be a challenge but you will get it done. I think it will be easier to find that diaphragm or even change out the rear axle, rather than engineer a mechanical selector solution.

Kent