Late C3 and C4 differential fill plug size/threads

69427

The Artist formerly known as Turbo84
Joined
Mar 30, 2008
Messages
2,972
Location
Clinging to my guns and religion in KCMO.
I'm adapting a C4 D36 batwing to my C3 differential to pull a few more pounds off the car. C3s have the fill port in the cover, while C4s have the fill plug in the differential housing, hence there's no built in way to fill the differential once these parts are bolted together. I need to drill and tap the C4 cover (somewhere), and if I have room I'd like to use the factory plug (otherwise I'll just use a smaller pipe plug in there somewhere). Anybody know what the thread size is for the fill plug in the C3 batwing and the C4 diff housing?

Thanks for any help!
 
If you go custom drill 2 holes. One for a level plug and another for a fitting and remote filler line. Much easier that way. As for the thread...no idea. Maybe metric but thought it was an npt size
 
ok not to hijack but WTH... where do I put the holes in the C3 Iron diff for my rear diff cooler set up... I cant find the specs and I know Ive seen them somewhere... oh never mind i found them in my 2nd edition Power manual 1/2in NPT :twitch::twitch: sucks to get old and CRS Syndrome

Be sure radius the edges of the holes nicely

I found some nice used NASCAR set ups and I will just run an 12V motor instead of the pinion shaft pulley,,,

:smash::smash::smash:
 
Last edited:
I was thinking 1/2 NPT was the right size, thanks for the confirmation. NPT is tapered, make sure you don't cut too deep with the tap.
 
Top