The Stovebolt Site Forums The Parking Lot Big Bolts Shopping for a shop manual

I'm seeing quite a few different shop manuals online for 1947-54 Chevrolet trucks. Which is the best?
Also, do any of them cover Hydrovac units? I got my rebuild kit and am making good progress but forgot to note which way the middle disc of the piston faces. Looks like the middle disk edges dish towards the bottom of the bowl. Going by the coloration from the leather on the disc. Which seems odd because that edge would be digging into the inner corner of the leather that way.

Also should the new leather be soaked in mineral oil. Thats what the video on YouTube did. Theres only one vid I could find on this type hydrovac, its on a 1950 6400. ( I guess Chevy went from 7" to 9 1/2" in 1950 because mine is 7" and his is 9 1/2". His number was 374550 and mine is 374980.

many thanks

There is an Old Online Chevy Manuals site. It has manuals for chevy trucks and cars. Check it out.

Thanks, the only thing I found there for hydrovac is the 49-52 Chevy shop manual, which has a good few pages on it but without pictures.
Doesn't explain enough of the terminology and no pictures. I'm going to ship it off, does anybody know of a good hydrovac rebuilder in the NW? I know of one in Massechusetts. I got the whole thing done except for the power piston, (I think thats what it's called, the big piston with the leather and three discs) So if anyone can explain how that goes together I can finish it.

I looked at the YouTube vid again and got it figured out now. The middle disc does have the dished edge biting into the leather

Glad to hear you sorted it out and saved the trip to the rebuilder. I didn't see your post about the assembly sequence question before you got it figured out. Sorry.

All that being said, I have a lot of Chevy and GMC original shop manuals and parts books. I found that the GMC books have a lot more detail when it comes to major component repair/rebuilding instructions with good diagrams to boot.

I've got a '47 GMC Shop Manual for the Model 300-450 trucks which use hydrovac units. The 300-350 models use the smaller 7" diameter unit while the 370-450 Models use the larger 9-1/2" units. Perhaps some of the GMC guys can comment on if the GMC smaller unit is the same design/compatible with the Chevy 7" hydrovacs??? If they are the same, I could try and share specific hyrdovac info to help out further.

Thanks Dan, I was curious why my 6400 didn't have a 9 1/2" and if maybe the 7" had the same bolt pattern as the 9 1/2 and someone swapped the smaller one into it. I'll just see how it works I guess and if it seems too weak I'll think about trying a 9 1/2. The nice thing about these is the ease of installation. It's all back together except for the control valve diaphragm. The kit I got had a different one entirely so I sent a picture of it to the store and they said the 347550 came in two types and they had the right diaphragm and could ship it out right away. So just waiting for that now.

Still wondering if I should take apart what is underneath of that control valve diaphragm or call it good. I did take apart all the stuff below that pressure cylinder and replace those parts. Thanks for the help and I'll let you know if I need any more help

I know you've probably moved on, but it you need more info on the Hydrovac maybe the 1955-2nd Shop Manual write-up will help.

It's on the same web site as the other manuals. Here's the link;

https://chevy.oldcarmanualproject.com/shop/1955truck2/55ctsm0526.htm

Mike B