Changing Differential Fluid

[76BBSub]

I wanted to address the questions on changing differential fluid from a previous thread that was closed.

I think if you check your owner's manual GM recommends changing the differential fluid at 15,000 miles the first time.  The interval then drops, if I recall correctly, but if you have a posi you want to stay on top of it.  The clutch packs will wear faster.

The best thing is to follow the "severe duty" schedule in your owner's manual.  Grease/oil is cheap compared to worn or broken parts.  I also used synthetic fluid when I changed the diff fluid in my Suburban.

Jeff

[96 Vortec]

Since the subject of fluid changes has come up, when should auto transmission fluid be changed?  Also, would you suggest changing the filter?  I know several people, mechanics and dealers, that think it is taboo to break the seal open on a transmission pan.  They prefer to use the vacuum systems to drain the pan and then just refill it.

[RyanbabZ71]

its not a posi

Its a locker that requires a special synthetic fluid

 

[MountaineerTom]

I don't know why it was closed either.  

I going to use Valvoline synthetic in the rear and regular valvoline gear oil in the front.  I was going to use synthetic in both, but the manual calls for regular in the front, so I think I'll stick with that.  At least till the warranty runs out.

[Guest Friz]

Quote: from 96 Vortec on 5:23 pm on Mar. 1, 2001

Since the subject of fluid changes has come up, when should auto transmission fluid be changed?  Also, would you suggest changing the filter?  I know several people, mechanics and dealers, that think it is taboo to break the seal open on a transmission pan.  They prefer to use the vacuum systems to drain the pan and then just refill it.

 

I've been working on cars for 25 years and that's the first time I've heard that one. My guess as to why someone would think that would be twofold;

1) Has had leaking problems from dropping the pan before. A lot of people (inexperience) will over tighten the pan bolts. This leads to pan distortion and leaks.

2) If you drop the pan and change the filter, you only end up changing the fluid that is in the pan, leaving old fluid in the torque converter. I've seen people run a hose from the input side of the tranny on the cooler line to a 5 gallon container of tranny fluid. The output from the cooler is run to an empty bucket. Start the motor and the tranny pump recycles ALL the fluid. I don't know how the Chevy place does it, but they changed my filter and used 5 quarts of fluid. I just checked the reciept.

[76BBSub]

Automatic transmission fluid should be changed every 15,000 to 30,000 miles depending on driving conditions and how picky you are.  As I mentioned before, grease and oil are cheap compared with major repairs, and changing the fluid regularly is the best preventive maintenance on an auto trans.  Alot of places drop the pan and change the filter.  If the dealer only replaced 5 quarts this is probably what they did.  Some of the oil change places will cycle all the fluid out, but I'm not sure about having those idiots touch something as sensitive as my transmission, they tend to break even simple things, like crowbars ;-)

Jeff