The Stovebolt Site Forums The Parking Lot Big Bolts 66 C60 GM-T170 2speed need Vacuum Diaphragm Replacment???

Hi guys I just pulled my vacuum diaphragm apart and found a huge hole, So now the trick is were to get one of these or use one from another type of truck or car for that matter that's close enough to do some mods to make it work............ ANYTHING PLEASE THIS DUMP IS A WORKING TRUCK!!!!!!! here is my dump its my pride and joy.

Some of the Chevrolet dealers in the Midwest still had some NOS ones in stock just a few years ago. If you can get a Chevrolet dealer to do it, they can find NOS stock. The last one I bought was at a Chev dealer in Kansas. At that time he still had several of them on hand.

Thank you Does anyone know what the part number is for that diaphragm and the little ring seal on shaft to keep oil from diff. getting in to vacuum unit or vice versa???

It looks like you could either have an Eaton 47638 which takes a GM 2398285 or a Bendix 374451 which takes a 3847058 GM. Are there any markings on the vacuum unit you have?

yes bendix

Last resort- - - -make a diaphragm. A piece of fabric-reinforced rubber gasket material the appropriate thickness can be cut to the shape of the old diaphragm and attached to the mechanical linkage in the center. If it's riveted instead of bolted together, any good machinist can drill and tap the shaft to accept a center bolt and some flat washers. Just be sure to Loctite the bolt that holds the assembly together. I used to make diaphragms for pneumatic valves that way frequently when I was a maintenance man for E&J Gallo winery.
Jerry

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=974858#Post974858 I posted this "How-To",a while ago. Hope it helps! Actually pretty easy and fun to do!

I know this is past your prime...but I just bought a complete used diaphragm from Holst Truck in Idaho. I also purchased a NEW rubber diaphragm ($55)from Inland Truck Parts in Billings, MT.

I know this is long after the original thread, but I happened to be looking for information on repairing the two speed diff in my 1957 Chevy 6100 Wrecker. I've been told by the shop that the diaphragm is brittle and cracked. I did find a place that has reproduction diaphrams.

http://www.rebuildersenterprises.com/

http://www.ebay.com/itm/2-SPEED-REAR-AXLE-DIAPHRAGM-GM-3847058-BENDIX-374451-/172542577743

GM 3847058 2 SPEED DIAPHRAGM

This is a brand new diaphragm manufactured for www.rebuildersenterprises.com

Fits GM 2 speed rear axles, Also replaces Bendix 374451.

O.D. is approx 7" I.D. is approx 3"


To see if this unit will fit your application or for technical assistance, feel free to call 800-489-9860.

Rebuilders Enterprises, Inc. is Illinois' Original Remanufacturing Company