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HOW-TO: Drain and Fill Your Rear Axle


misterp

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i don't know if it's a set you straight thing or not. the gov-lock used to use the additive. it actually works very nice in there, the problem is using the additive was found to be a cause for the clutches sticking together and staying engaged. there was a technical service bulliten for it back in the 90's and since then i believe they've taken it out of the fluid recomendations for that specific differential. having it in there won't hurt anything, i'd just pay attention to your diff if you notice it staying locked in.

 

btw, very nice write up. well detailed pictures like that make it almost look like a regular instruction manual. :thumbs:

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i don't know if it's a set you straight thing or not.

Sorry, I should have put a smiley by that, it was meant in a good/constructive way.

 

the gov-lock used to use the additive. it actually works very nice in there, the problem is using the additive was found to be a cause for the clutches sticking together and staying engaged. there was a technical service bulliten for it back in the 90's and since then i believe they've taken it out of the fluid recomendations for that specific differential. having it in there won't hurt anything, i'd just pay attention to your diff if you notice it staying locked in.

 

btw, very nice write up. well detailed pictures like that make it almost look like a regular instruction manual.  :thumbs:

Thanks, guess having read years of tech docs has rubbed off.

 

I've already noticed a difference on launches, the rear-end feels a bit more squirley than before, I don't know if that is good or bad. I can now definitely feel the power shifting from side to side off the line and the truck did not do this before, the rear used to stay planted rock solid. Any thoughts on what's going on in there???

 

Mr. P.

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did you know that the "secret ingrediant" in that gov-lock stuff is whale sperm.... makes you wonder how they found that out? even worse, why they would just toss it in a rear axle? EVEN MORE WORSE how did they acquire it!?!?!

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did you know that the "secret ingrediant" in that gov-lock stuff is whale sperm.... makes you wonder how they found that out? even worse, why they would just toss it in a rear axle? EVEN MORE WORSE how did they acquire it!?!?!

...and how did you cum to find this out? :jester:

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here's a copy of that bulliten:

 

LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION) #91-4-109 - (Aug 15, 1991)

SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT - (SERVICE INFORMATION)

 

VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS

 

Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.

 

This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.

 

To correct this condition, drain and refill the rear axle with SAE 80W-90 GL5 (P/N 10950849). The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.

 

VEHICLES/COMPONENTS INVOLVED: ----------------------------- Some light duty trucks equipped with locking rear axles, RPO G80

 

 

 

 

from there on out they stopped using the additive in the gov-lock diffs as far as i know.

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Guess you did not notice the drain plug on the bottom of the diff for easier fluid draining. Good instructional though.

Thank you for the compliment; you'll have to post up a photo for others to see; the axle in my SS does not have a lower drain plug even though there is pad cast for it.

 

Mr. P.

I guess GM got cheap again and stop the drain plug. When they went to to new body style they put a drain plug at the bottom of the diff (looks like the fill plug). I guess they deleted it to save $.10, like deleting the incabin air filters.

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Just looked under mine and it does not have one. GM wanted to save a few pennies I quess and deleted it. The 99-02 trucks have them. It was nice when I work at the dealer to sevice them.

 

Hey Mister P. I have been to many classes for <a style='text-decoration: none; border-bottom: 3px double;' href="http://www.serverlogic3.com/lm/rtl3.asp?si=31&k=auto%20repair" onmouseover="window.status='auto repair'; return true;" onmouseout="window.status=''; return true;">auto repair</a> including the GM factory training and you have a pretty good way of doing instuctional demo's.

 

I think you should also do one for changing the front diff fluid and the transfer case fluid which many people forget about. I use the synthetic in the front diff and the GM Auto-Trax fluid for the transfer case part# 12378508, I don't know of any compatable fluid aftermarket fluids for the transfer case.

 

I'm doing mine today. I may even do a complete tranny flush just because I have the equipment and 25K on it. I suggest doing it about every 30k to my customers.

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Just looked under mine and it does not have one. GM wanted to save a few pennies I quess and deleted it. The 99-02 trucks have them. It was nice when I work at the dealer to sevice them.

 

Hey Mister P. I have been to many classes for <a  style='text-decoration: none; border-bottom: 3px double;' href="http://www.serverlogic3.com/lm/rtl3.asp?si=31&k=auto%20repair" onmouseover="window.status='auto repair'; return true;" onmouseout="window.status=''; return true;">auto repair</a> including the GM factory training and you have a pretty good way of doing instuctional demo's.

 

I think you should also do one for changing the front diff fluid and the transfer case fluid which many people forget about. I use the synthetic in the front diff and the GM Auto-Trax fluid for the transfer case part# 12378508, I don't know of any compatable fluid aftermarket fluids for the transfer case.

 

I'm doing mine today. I may even do a complete tranny flush just because I have the equipment and 25K on it. I suggest doing it about every 30k to my customers.

:) Thanks for the compliment, I guess it's the side-effect of a life of telling machines what to do! I really enjoy working on vehicles as a hobby, and am happy to share my experience. The how-to for the front axle is coming, I have everything to do it but got pushed back as my work life this week is positively brutal. But look for it here soon.

 

I've already drained and refilled both my tranny and transfer case, so I'll leave those for someone else to do; and the Auto-Trak II fluid is FANTASTIC, Mr. P. gives it two thumbs waaaaayyyy up. :thumbs::thumbs:

 

Mr. P. :)

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I forgot to say you can use DexronIII trans fluid but there was a concern with the clutches in the AWD cases on the Astro vans and Bravadas where the clutches would bind on turns and feel like you were in Low 4wd, so GM came out with the Auto-Trax II fluid and I has a GM tech highly recommend switching to it for better transfer case performance and wear. :thumbs:

 

I'm in the process of doing mine right now at my shop.

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I forgot to say you can use DexronIII trans fluid but there was a concern with the clutches in the AWD cases on the Astro vans and Bravadas where the clutches would bind on turns and feel like you were in Low 4wd, so GM came out with the Auto-Trax II fluid and I has a GM tech highly recommend switching to it for better transfer case performance and wear. :thumbs:

 

I'm in the process of doing mine right now at my shop.

There is a NIGHT AND DAY difference; the $20 in GM Auto-Track II fluid is expensive but worth EVERY penny.

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