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What size is the fill plug on an NV4500?

GM Guy

Manual Trans. 2WD Enthusiast
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Hey guys,

I am in town (in Idaho this time), and the parts lady is out, so they took down my info and will return my call. I am doing some internetting over at the library, and would prefer not to run home just to measure a damn plug that i should have measured in the first place.

So, I ask you fine folks, what size is the fill plug on a NV4500? Is it 3/8 or 1/2 inch? I know its a pipe plug, and am fairly certain its 1/2 inch.


also, what square drive normally goes with the plug size? I know I use a 3/8 ratchet to check the rear end, but its a rather small plug. is it a 3/8 plug?

what I am doing is ordering magnetic drain plugs. I do not want to stress the poor 93 any more,(still running crappy, but starts good cold and little to no oil consumption (1 qt towing hard) and little blowby, so I think the motor is fine but it still has the horrible timing and possible bad IP) and I have been wanting to pull the service body off the 95 GMC for a while, so I am going to pull the body, buy a B&W turnover ball, make some mudflaps and fenders, wire up some lights, and pull the gooseneck with the 95 hauling the 93.

the tranny doesnt sound the best in the 95, so I figured throw a magnetic plug in it in case there is a bit of grit in there. cant hurt. (and yes, changing oil would be a much smarter idea. no oil and no money! :D plus, the tranny is painted grey, so I am thinking it was a cheapie rebuild exhange with import parts that are coming apart. I have a original out of a 95 1500 gasser that I plan on melding with an older one for the lower gears and making the ultimate tranny for the 95, so I am in no mood to preserve this one.)

so, any input on the plug size, input on whether or not a NV4500 can completely grenade (I need to record the noise this one makes, hopefully just gear harmonics, as its mostly on decelleration, but sounds aweful nonetheless), etc. appreciated.
 
Its dark and my calipers haven't been turned on in a long time the battery symbol came on and the numbers are dim but I measured the largest point of the plug just outside of the plastic tag and measured about 0.960 so I am guessing its 1/2 NPT.

Definately not 3/8 and I don't think its 3/4 but according to this page its right in middle of outside diamter between 1/2 and 3/4.

http://machiningproducts.com/html/NPT-Thread-Dimensions.html

And my '97 has a internal hex "allen head" missed that part of question sorry gotta go help put kids in bath and in bed.
 
thank you very much!

1/2 inch it is! I know dad has one in his, so it had to be a common size.

I like the factory look of the factory plug, but I am not too keen on packing extra tools just to check the oil. using a ratchet alone would be nice.
 
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