My '79 W150 has an 8 3/8 rear R&P. It's seeping a bit of fluid from the diff, even though I recently serviced it. I'm going to pop the cap off again soon, and have a closer look to see if the cap is bent along the lip. I don't see any listings for new caps for 8 3/8, so I'm wondering if it uses same cap as the 8 1/4? Randy's Ring and Pinion website doesn't even show listing for one. Only shows 8.25 and 9.25 for '79 W150. I believe both are 10 bolt, so maybe same cap for both 8's? I want to be ready to purchase one if needed. Thanks.

Larry

Do you need the rubber fill plug? If yes it is the same part number as the 8 1/4 car plug. I have a couple nos plugs. I can mail you one for free if you can`t find it local. 3723687

I think he's talking about the sheet metal cover.

I appreciate that but no, I'm talking about the actual cover. 10 bolt cover. Sorry for confusion and Thank you.

This is all that's listed for covers. Copy and paste didn't work

www.randysworldwide.com/diff-wizard/?diffyear=1979&make=Dodge&model=W150+1%2F2+Ton+4x4&drivetype=Rear+Diff+-+4WD

Someone can correct me if I’m wrong, but I was always under the impression that the 8 1/4 and 8 3/8 were one and the same. Just that the 8 3/8 was called that for truck use for some reason

Easy to find are the chrome ones. The plain metal ones not so much. 4049689. 8 1/4 and 8 3/8 are the same as far as i know.

Actually here is a black one. https://www.ebay.com/itm/Chrysler-8...r-Mopar-Dodge-8-1-4-10-bolt/183876552382

Dorman 697-709 black steel rubber plug under $30

Spectre Performance 6093 chrome, screw in plug under $25

I had no trouble finding 8.25 ones. I just need to be sure they are indeed the same (8 1/4 and 8 3/8) before ordering one. What an oddity that Chrysler would confuse things this way if they are the same. My FSM shows 8 3/8.

Thanks.

The mopar part number for the cover is the same for 8 1/4 and 8 3/8. The earlier 8 1/4 part number 2852921 from a 74 passenger car parts book for the cover interchanges with the 8 3/8 4049689 that is listed in the 78 truck book.