Differencial fluid
Melting Slicks
Joined: Jun 2005
Posts: 2,239
Likes: 74
From: Palatine, Peoples Republic of Illinois
St. Jude Donor '09-'10-'11-12-'13-'14-'15-'16-'17-‘18
NCM Sinkhole Donor
I always check the fluid level with each oil change, but I don't change the fluid. Unless you're racing the car there shouldn't be anything to contaminate the fluid except what ever might wear from the clutch packs.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
It should last at least 50,000 miles or 5 years [whichever comes first]. If you are a fanatic about changing oil frequently, make it 25,000 or 3 years. [It doesn't have a drain plug, does it?]
Intermediate
Joined: Feb 2006
Posts: 30
Likes: 0
From: ellisville mo
I changed mine when I started getting a little growl from the area of the differential. It seemed to get more pronounced when turning in reverse or turning very slowly in forward. We used an additive (can't remember the name) and this solved the problem. This problem happened about 10 years and 12,000 miles ago and has not returned.
We enjoyed meeting you at the Shark C3 show. I have the brown 79.
We enjoyed meeting you at the Shark C3 show. I have the brown 79.
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Thread Starter
Melting Slicks
Joined: Mar 2009
Posts: 2,885
Likes: 1
TWA747/79 - 
It was great talking with you and your wife too!
I looked up rear axle lub change in the GM Service Manual and it says "normally doesn't require to be changed for the life of the vehicle" - except if "pulling a trailer, change ever 15,000." I wonder how GM defines how long the vehicle is suppose to last.
It was great talking with you and your wife too! I looked up rear axle lub change in the GM Service Manual and it says "normally doesn't require to be changed for the life of the vehicle" - except if "pulling a trailer, change ever 15,000." I wonder how GM defines how long the vehicle is suppose to last.
Burning Brakes
Joined: Aug 2006
Posts: 1,155
Likes: 0
From: San Diego California
I just had the Dana 44 rebuilt in my 80- deeper gears, new seals and rebuilt posi. The shop, ProGear, in San Diego, does nothing but rearends, and did a great job. Its good to feel better acceleration, and no more oil being slung around the rear exhaust pipes and on the garage floor. They recommend changing the oil every 50K miles. Thats when I did mine last- and it was pretty black and gritty before the rebuild. I'll watch it a little more frequently and change it earlier if needed. They also strongly recommend against using synthetic oil, and do recommend using the heavier dino rear gear oil- 90 140 , with the posi additive.