Rear Gear Oil - Help Needed

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Jan 5, 2013 | 05:29 PM

jmeisinger

Thread Starter

Heel & Toe

Joined: Jan 2007

Posts: 24

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From: Connecticut

Rear Gear Oil - Help Needed

I was planning to change my rear gear oil in my '96 convertible today. I read the owners manual to confirm exactly what I needed to do. I got two quarts of Royal Purple 75W90 gear oil and a pump attachment to be able to get it up into the fill hole.

To start, I opened the fill plug to be sure I could refill the system once I drained the differential. The fluid was right to the bottom of the fill hole.

I then unbolted the drain plug and removed it, but nothing came out (and yes, I unbolted the correct bolt).

I was wondering if this happened to anyone else and if anyone has any idea why the rear differential is not draining. Any thoughts / ideas would be appreciated.

Joe

Jan 5, 2013 | 05:40 PM

JackDidley

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From: Database Error Indiana

Thats not really a drain bolt. You have to use a suction gun to get the gear oil out.

Jan 5, 2013 | 05:48 PM

jmeisinger

Thread Starter

Heel & Toe

Joined: Jan 2007

Posts: 24

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From: Connecticut

Quote:

Originally Posted by JackDidley

Thats not really a drain bolt. You have to use a suction gun to get the gear oil out.

Really? According to the Chilton Manual, it indicates it is the drain plug. I guess I will have to invest in a suction gun and tube to get all the old fluid out. Thanks so much for the insight.

Jan 5, 2013 | 05:51 PM

93Rubie

Safety Car

Joined: Sep 2010

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From: Indiana PA

Take that Chilton's Manual and use it as a poor excuse for back up toilet paper. Those and Haynes manuals are about worthless. Get a GM Factory Service Manual, much better. See Ebay, For Sale Section, etc....

Jan 5, 2013 | 06:04 PM

96_vette

Racer

Joined: Jun 2007

Posts: 459

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From: Hawaii

Quote:

Originally Posted by 93Rubie

An FSM is the best choice. I replaced my gear oil about a year ago. I got a hand pump to suck out all of the old gear oil and replace with the new oil. Make sure you get the friction modifier additive (Limited slip additive). Some brands already have this in it such as royal purple. I used Mobil 1 full synthetic gear oil and 4 oz of limited slip additive.

Jan 5, 2013 | 06:06 PM

RollaMo-LT4

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From: Rolla Missouri

2021 C4 of the Year - Unmodified Finalist

St. Jude Donor '10 thru '25

Quote:

Originally Posted by JackDidley

Thats not really a drain bolt. You have to use a suction gun to get the gear oil out.

No drain plug on your differential.

Quote:

Originally Posted by jmeisinger

Really? According to the Chilton Manual, it indicates it is the drain plug.

Take your car and let "Chilton" get the fluid out then.
Sorry, couldn't resist.

Quote:

Originally Posted by 93Rubie

Link to factory service manual:
http://www.helminc.com/helm/product2...96Y&itemtype=N

Jan 5, 2013 | 06:09 PM

c4cruiser

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From: Lacey WA RVN 68-69

NCM Sinkhole Donor

The "pump attachment" you bought to do the filling can also be used to suck the old gear oil out. Just get a length of vinyl hose that fits over the pickup tube of the pump, and stick the open end into the diff carrier.

A few of the aftermarket Corvette parts suppliers carried a drain plug "kit" that allowed for gravity draining, but it required that you drill a hole into the carrier and it had to be in just the right place so it didn't hit the rig gear. The included plug was a self-tapping part so you had to be careful when screwing it in.