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#1465286 - 05/15/09 10:42 AM gear oil and transfer case fluid for my silverado`
matthewbl87 Offline


Registered: 05/15/09
Posts: 2
Loc: Cali
I'm the proud owner of a 2000 Chevy Silverado ext. cab 4X4 Z71 with a push button controled transfer case. A few weeks ago I broke 50,000 miles on the odometer and I need to change the transfer case fluid and differential fluid and change the transmission fluid and filter as well. Ive done a little bit of research on the topic and I know that GM recomends using 80W-90 in the front dif. and 75W-90 in the rear. I want to use Royal purple gear oil for both diffs but RP only sells 80W-90 gear oil in 5 Gal buckets which is way too much for the job so would it hurt to use 75W-90 or any other weight gear oil in the front diff??? I also know that if the differentials are lockers that I need to put additives into the lubricant so does anyone know how I can find out what type of diffs that I have??? And if my diffs are lockers what types of additives do I need to add to the gear oil???

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#1465296 - 05/15/09 10:51 AM Re: gear oil and transfer case fluid for my silverado` [Re: matthewbl87]
chevrofreak Offline


Registered: 06/17/05
Posts: 4899
Loc: Billings, MT
IMO, you'd be better served using Amsoil Severe Gear 75-90 front and rear.
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#1465303 - 05/15/09 10:57 AM Re: gear oil and transfer case fluid for my silverado` [Re: chevrofreak]
94supraonchrome Offline


Registered: 10/14/08
Posts: 318
Loc: Kentucky
you could use 75W90 RP in both diffs.....
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Havoline
Royal Purple
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#1465311 - 05/15/09 11:03 AM Re: gear oil and transfer case fluid for my silverado` [Re: chevrofreak]
Bill in Utah Offline



Registered: 11/11/02
Posts: 12782
Loc: UT
 Originally Posted By: chevrofreak
IMO, you'd be better served using Amsoil Severe Gear 75-90 front and rear.
I'd agree but he wants RP.

I'm not sure about the lockers and if RP needs a additive. call them.

On the front diff, look at the vent plug. 100% of them need to be updated IF YOU RUN syn (conventional was the factory fill) as they WILL leak and have issues.

I think the stock one is white and the new one is black. A parts person at the dealership can tell you.

For the transfer case, you have to use the GM stuff.

75-90 or 80-90 will be fine for both ends.

Take care, bill

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#1465369 - 05/15/09 11:54 AM Re: gear oil and transfer case fluid for my silverado` [Re: Bill in Utah]
Jim 5 Offline


Registered: 05/25/05
Posts: 4009
Loc: Calgary Canada
Thanks for that tip Bill. My vent plug on my truck has the black one. I believe canadian spec trucks call for 75w-90 gear oil from the factory.
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07.5 GMC Sierra 2500HD LMM Rotella 15w-40
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#1465444 - 05/15/09 12:51 PM Re: gear oil and transfer case fluid for my silverado` [Re: Jim 5]
Kestas Offline



Registered: 06/04/02
Posts: 10786
Loc: The Motor City
I just did this job for my neighbor's 01 Silverado. On the differentials, remove the fill plugs first, then proceed. The rear fill plug was a bear to get off. I couldn't do it by hand.

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#1465509 - 05/15/09 01:54 PM Re: gear oil and transfer case fluid for my silverado` [Re: Kestas]
Mike_dup1 Offline


Registered: 11/17/02
Posts: 3011
Loc: USA-Michigan
 Quote:
I also know that if the differentials are lockers that I need to put additives into the lubricant so does anyone know how I can find out what type of diffs that I have??? And if my diffs are lockers what types of additives do I need to add to the gear oil???



DO NOT add any additives to the locking differential. Those are designed for Limited Slip Differentials which are normally installed in cars and AWD vehicles. Trucks with G80 use a locking rear differential and the use of any additive can delay the locking and cause damage to the differential.

If you have a locking differential on your truck the label in the glove compartment will have a list of option codes, if G80 is on that list its a LOCKER, if no G80 means a open axle.
_________________________
2012 Sierra Denali CC 6.2L AWD
2009 Cadillac CTS4
2010 John Deere X728SE
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#1466079 - 05/15/09 11:59 PM Re: gear oil and transfer case fluid for my silverado` [Re: Mike_dup1]
matthewbl87 Offline


Registered: 05/15/09
Posts: 2
Loc: Cali
DO NOT add any additives to the locking differential. Those are designed for Limited Slip Differentials which are normally installed in cars and AWD vehicles. Trucks with G80 use a locking rear differential and the use of any additive can delay the locking and cause damage to the differential.

If you have a locking differential on your truck the label in the glove compartment will have a list of option codes, if G80 is on that list its a LOCKER, if no G80 means a open axle.
_________________________

Thank alot for this advice Mike. I checked the glove box and it says "G80" on the parts list. Does this mean that both the front and rear differentials are Lockers??? assuming that both the front and rear differentials are lockers will I be good to use the same weight gear oil in both differentials???

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#1466082 - 05/16/09 12:03 AM Re: gear oil and transfer case fluid for my silverado` [Re: matthewbl87]
Ryan02SS Offline


Registered: 12/20/06
Posts: 62
Loc: Formerly Ryan00TJ member 143
Nope G80 is just the rear. I changed out my factory oil in mine to Mobil 1 75W-90 Syn front and rear. The GMT900 platform uses Dexron VI in the transfer case instead of the AutoTrac fluid like the GMT800's.
_________________________
08 GMC Sierra Z71 LY5 5.3L M1 0W-30 AFE PureOne
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#1466201 - 05/16/09 06:31 AM Re: gear oil and transfer case fluid for my silverado` [Re: matthewbl87]
NHHEMI Offline


Registered: 07/06/07
Posts: 5122
Loc: NH
 Originally Posted By: matthewbl87
I'm the proud owner of a 2000 Chevy Silverado ext. cab 4X4 Z71 with a push button controled transfer case. A few weeks ago I broke 50,000 miles on the odometer and I need to change the transfer case fluid and differential fluid and change the transmission fluid and filter as well. Ive done a little bit of research on the topic and I know that GM recomends using 80W-90 in the front dif. and 75W-90 in the rear. I want to use Royal purple gear oil for both diffs but RP only sells 80W-90 gear oil in 5 Gal buckets which is way too much for the job so would it hurt to use 75W-90 or any other weight gear oil in the front diff??? I also know that if the differentials are lockers that I need to put additives into the lubricant so does anyone know how I can find out what type of diffs that I have??? And if my diffs are lockers what types of additives do I need to add to the gear oil???


RP 75W-90 will work GREAT in both your front and rear diff's even if you have the Eaton G80 in the rear. I had 2 Silverados's( 05 & NBS 07 - Ext Cab 4WD's as well )with the G80 and used RP 75W-90 front and back and it worked great. RP is every bit as good as Amsoil. RP is an excellent choice you made. \:\!

As to your t-case. If you have the push buttons on the dash that means you have the AUTO 4WD option t-case and you should ONLY use GM Autotrak II fluid. There is NO aftermarket replacement for it. Double check your owner's manual in the back to make sure it calls for that special fluid but I am 99.9% sure it does. Never seen a t-case with the push buttons and AUTO 4WD mode that doesn't call for it.


Edited by NHHEMI (05/16/09 06:32 AM)
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#1533866 - 07/16/09 09:46 AM Re: gear oil and transfer case fluid for my silverado` [Re: NHHEMI]
Burbanite Offline


Registered: 11/28/05
Posts: 125
Loc: North Vancouver BC
[quote=NHHEMI]
 Quote:


As to your t-case. If you have the push buttons on the dash that means you have the AUTO 4WD option t-case and you should ONLY use GM Autotrak II fluid. There is NO aftermarket replacement for it. Double check your owner's manual in the back to make sure it calls for that special fluid but I am 99.9% sure it does. Never seen a t-case with the push buttons and AUTO 4WD mode that doesn't call for it.


RP Synchromax is a synthetic substitute for Autotrac II fluid. They have it listed on their website as such and I've read about a few people who have used it in their T-Cases, that were supposed to use Autotrac II Fluid, with great success.


Edited by Burbanite (07/16/09 09:47 AM)

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#1533968 - 07/16/09 11:38 AM Re: gear oil and transfer case fluid for my silverado` [Re: Burbanite]
Ken2 Offline


Registered: 12/02/02
Posts: 6126
Loc: Washington St.
The limited slip differential friction modifier additive is only needed for clutch-type limited slip differentials, not for lockers, Torsen, or other types.

Just about every gear oil blended for differentials already has the correct amount of additive in it if the label says that it is suitable for limited slip differentials. More should only be added if the differential is grabby.
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#1538539 - 07/20/09 06:43 PM Re: gear oil and transfer case fluid for my silverado` [Re: NHHEMI]
artificialist Offline


Registered: 09/23/07
Posts: 6714
Loc: Florida
RP gear oil already has the LS additives in it.
_________________________
2010 Lancer Ralliart Sportback

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#1543284 - 07/24/09 11:06 PM Re: gear oil and transfer case fluid for my silverado` [Re: Burbanite]
gmctodd Offline


Registered: 11/29/07
Posts: 225
Loc: Happy Valley, PA
 Originally Posted By: Burbanite
[quote=NHHEMI]
 Quote:


As to your t-case. If you have the push buttons on the dash that means you have the AUTO 4WD option t-case and you should ONLY use GM Autotrak II fluid. There is NO aftermarket replacement for it. Double check your owner's manual in the back to make sure it calls for that special fluid but I am 99.9% sure it does. Never seen a t-case with the push buttons and AUTO 4WD mode that doesn't call for it.


RP Synchromax is a synthetic substitute for Autotrac II fluid. They have it listed on their website as such and I've read about a few people who have used it in their T-Cases, that were supposed to use Autotrac II Fluid, with great success.


WRONG!

If you have a button labeled AUTO you have a Automatic transfer case and need the autotrac II fluid. If you have push buttons(or a dial) labeled 2wd,4HI, and 4LO no mention of auto mode. You have a Electric shift t-case and use ATF. It will not hurt to use the AutotracII fluid in a non auto t-case, but it is expensive.
_________________________
Todd

06 GMC Sierra 3500 D/A DRW-Wolfs head Extreme duty/Fram TG
08 Envoy-Wolfs Head Super duty 5w30/PL25288


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#1543354 - 07/25/09 12:06 AM Re: gear oil and transfer case fluid for my silverado` [Re: gmctodd]
Burbanite Offline


Registered: 11/28/05
Posts: 125
Loc: North Vancouver BC
 Originally Posted By: gmctodd
 Originally Posted By: Burbanite
[quote=NHHEMI]
 Quote:


As to your t-case. If you have the push buttons on the dash that means you have the AUTO 4WD option t-case and you should ONLY use GM Autotrak II fluid. There is NO aftermarket replacement for it. Double check your owner's manual in the back to make sure it calls for that special fluid but I am 99.9% sure it does. Never seen a t-case with the push buttons and AUTO 4WD mode that doesn't call for it.


RP Synchromax is a synthetic substitute for Autotrac II fluid. They have it listed on their website as such and I've read about a few people who have used it in their T-Cases, that were supposed to use Autotrac II Fluid, with great success.


WRONG!

If you have a button labeled AUTO you have a Automatic transfer case and need the autotrac II fluid. If you have push buttons(or a dial) labeled 2wd,4HI, and 4LO no mention of auto mode. You have a Electric shift t-case and use ATF. It will not hurt to use the AutotracII fluid in a non auto t-case, but it is expensive.


Well, Sorry to burst your bubble Dude, but I've been using RP Synchromax in my 246 T-case now for over 8 months with great success. In fact I just took it apart to do the Pump Rub Fix and the clutches are in perfect shape. I know one guy on FSC that's got over 60K on his 246 with Synchromax and it's still running strong. Since Synchromax is a full synthetic fluid and Autotrac II isn't, plus it cost less than the Autotrac II it's a no brainer as to what I'm going to keep using. Don't knock it until you try it.

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