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Topic: Diff filler plug

in Forum: C3 Driveline Components


Diff filler plug

Posted: 1/20/07 5:27pm Message 1 of 9
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New Zealand
Joined: 3/26/2005
Posts: 232
Vette(s): Silver '81 mostly original C3. Silver interior, bilstiens, big sway bars, headers.
I popped the plug out to check the diff oil level, and didn't pay attention to how the plug sat before I started. So now I have a question... the plug has a flat on its outer under which the red plastic warning tag sits. When the plug is installed and done up firm, should the plug have gone all the way in so the plastic tag is held tight between the flat on the plug and the diff housing, or does the plug flat sit proud of the diff housing by an eigth of an inch or so so the red plastic tag flops around instead of being "clamped" by the plug ?

From the look of the plug it seems it should wind all the way in and well clamp the plastic tag in the process. But mine didn't and maybe that is right... but I sure would like to know for sure one way or the other !

Thanx, Kiwi Chris


Kiwi Chris

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Diff filler plug

Posted: 1/20/07 5:53pm Message 2 of 9
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
The tag should be loose on the plug. If you manage to get the plug all the way down against the diff housing, something's wrong! The plug has a "pipe" thread, which means it is not the same diameter all the way down. It tapers a bit...smaller at the threaded end than at the square wrench end. This is what seals it. The threads should tighten more the farther in you twist the plug. Your's is fine.


Joel Adams
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Diff filler plug

Posted: 1/20/07 7:19pm Message 3 of 9
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New Zealand
Joined: 3/26/2005
Posts: 232
Vette(s): Silver '81 mostly original C3. Silver interior, bilstiens, big sway bars, headers.
Phew !   Thankyou for that. I was a wee bit worried...



Kiwi Chris

Diff filler plug

Posted: 1/20/07 7:39pm Message 4 of 9
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New Zealand
Joined: 3/26/2005
Posts: 232
Vette(s): Silver '81 mostly original C3. Silver interior, bilstiens, big sway bars, headers.
This wee worry was the grand finale to a nice simple job turning into an expensive waste of time - and I don't mind sharing the gory details even if it does make me dumbass of the month !

The mission - check the diff oil level. Simple enough one would think. Problem number 1... what size allen key is it ? Search the various workshop manuals, none of them say. (I should have asked on this site of course !) Anyway went shopping, ordered in a set Allen sockets, figured they would always be handy. And so they arrived, went to use them - one was a bit small, the next too big. Did you know Allen's come in Metric AND AF ? I didn't, and of course I was now the proud owner of a set of metrics. Yay.

Worked out it was a 3/8 inch Allen I needed, back to the shop and bought one - the usual L shaped version. Back home, to discover my latest purchase wouldn't get to the plug due to its awkward location and all the bits in the way.

So bak to the shop I go, can I purchase a 3/8 inch Allen socket ? No sir, sorry you can only buy the complete set. So I buy the set and finally manage to pull the plug. And out starts dripping the oil, which of course means it is full and the whole exercise has been an expensive waste of time !

So $100 later I have the most awesome selection of Allens now !!!    


Kiwi Chris

Diff filler plug

Posted: 1/20/07 7:51pm Message 5 of 9
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Lanoka Harbor, NJ - USA
Joined: 12/21/2006
Posts: 828
Vette(s): 1975 metallic blue coupe with t-tops,L48, t/t steering, black leather interior. 1990 L98, white/red leather interior, auto,a/c
besides having some new toolsClap you have to look at it as it is better to be safe than sorry. guess i lucked out, on my 75 it is a square head nut on it and a crows foot on the end of a long extension works great. now i am wondering if the plug on mine is a replacement or did they change the style? 


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Diff filler plug

Posted: 1/20/07 10:29pm Message 6 of 9
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
The cast iron diffs. had the square ended plugs, the aluminuminum diffs have the inverted allen head plugs.


Joel Adams
C3VR Lifetime Member #56    

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Diff filler plug

Posted: 1/21/07 6:51am Message 7 of 9
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Lanoka Harbor, NJ - USA
Joined: 12/21/2006
Posts: 828
Vette(s): 1975 metallic blue coupe with t-tops,L48, t/t steering, black leather interior. 1990 L98, white/red leather interior, auto,a/c
thanks joel. great to know that is something that wasn't screwed up. wouldn't have surprised me if the people used duct tape to cover the opening.Smile. one other question, is there a certain amount of the additive to put in if you are changing the gear oil? thanks


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Diff filler plug

Posted: 1/21/07 8:08am Message 8 of 9
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North Charleston, SC - USA
Joined: 3/20/2004
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Vette(s): 1975 L48 AT AC T-top
I bottle of GM additive. It is only a few ounces.
Scott



Diff filler plug

Posted: 1/21/07 10:12am Message 9 of 9
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

One is the recommended ratio. Lots of folks will put two(like me), but it could be considered overkill.


Joel Adams
C3VR Lifetime Member #56    

My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

in Forum: C3 Driveline Components


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