Forum Guru's, I've found a transmission tail shaft extension that allows a oil seal to be installed to prevent the trans oil from going into the torque tube. The number provided is GM 3845020 CASTING. I've never seen one of these and wonder if anyone knows if this was an upgrade or option and if there is any way to tell what size oil seal it would take as the seller doesnt' have any info on the seal. Thanks
Be sure you know what you're getting into , this same tranny was used in open driveline trucks too and they simply changed the rear extension housing , it cannot be used with a torque tube rear end.... Pix will prolly help here .
Thanks Thanks Nate, I knew you probably had some information on this thing. Sorry I don't have any pics of the thing. I thought I might pick it up as a nice to have in case I wanted to change to an open drive line later on without changing transmisssions. Do you know anything about what years it was used and on what so I can see if I can find the right seal for the thing?
Sticking My Head Out...... I'd say '54.2 ~ '67 , this is for the floor shifted Muncie SM420 tranny . As these trannies are still available for $50 complete anywhere , I'd not pay much for this part alone . The old seal will have the correct P/N moulded into it in raised numbers, wipe it clean and mark the #'s down before prying the old seal out . I've noticed the seals have <magic> shrinking numbers moulded into them , I easily read them 40 years ago but they're *so* much smaller now..... . If you want to do this , watch the Task Force pages and when yet another fool Hot Rods his perfectly good truck , grab the tranny , it weighs 350 # and so is hard to sell unless you know Jeep guys . This way you'll have a ready to go closed drive tranny and drive shaft , if you're really ambitions you can take 'em both apart & mix 'n match to get the best bits for long life & never any problems .
Muncie Thanks Nate, I have the regular 3 on the tree which is a saginaw trans right? I have to get street smart on the Muncie's. I'll check the archives for messages on swaps and stuff. I don't think I'll go for purchaseing the part if the Muncies are that plentiful and priced right to begin with.
Oh , Dang I stuck my head out and was wrong as usual . The Saginaw three speed is an entirely different animal . Maybe Joe will jump in here and give you the straight skinny including pictures...
Good Information Nate, The info you gave me was great. I learn something everytime you respond to an inquiry. I have even taken to saving the responses for future reference so don't stop helping us less knowledgable minions... I found the information about the transmission a great option for going to an open drive line if I decided to and I now know about the transmission extension part that I was interested in. Not to mention you save me $40 bucks in the process. So to sum up my response THANKS again for the information.
Casting 3845020 Your casting # , Support Assembly, is listed under GP 4.317 1954-55.1 3/4, 1 ton (heavy duty) http://chevy.oldcarmanualproject.com/1929_57chevyparts/57cmpc0396.htm The seal is in GP 4.318 seal is stamped 354021
Thanks Thanks for the information. My book only goes to 1950 on the parts which is why I couldn't find it I guess......I wonder if it can be used on the half ton. ANyway thanks again for the info
