GL-4 or GL-5?

[BlindBaby]

I have a 2009 Chevrolet Silverado 1500 and the owners manual calls for SAE 80W-90 for the front axle and SAE 75W-90 for the rear axle.

1. How do I determine if I need GL-4 or GL-5 oil?

2. How do tell if I have a limited-slip differential?

3. Why would GM spec a conventional oil for the front differential and a synthetic for the rear?

4. Does anyone know where to purchase Pennzoil gear lube other than on Amazon?

 

[PandaBear]

1) Depends on if you have synchros or LSD, or neither.

2) You will know if you have one (sport car)

3) They can't get away with conventional due to the stress in the rear, or they would do conventional at the rear too to save a buck.

4) Does it have to be Pennzoil gear lube?

 

[BlindBaby]

1. I don't have a clue what your talking about.

2. I assume LS in only in sports cars?

3. I assume I could run synthetic in the front as well as the rear.

4. I would prefer it, but I could go with Mobil

 

[Bluestream]

Originally Posted By: BlindBaby
1. I don't have a clue what your talking about.

2. I assume LS in only in sports cars?

3. I assume I could run synthetic in the front as well as the rear.

4. I would prefer it, but I could go with Mobil


Yes to all of the above except #2

 

[bullwinkle]

1. Check your owner's manual, but many newer gear oils cover both specs.

2. GM LSD axles usually have a tag that indicates if the axle needs LSD lube, or run your RPO codes in the glove compartment. Or find a slippery surface & punch it!

3. Rear axles generally get syn because they're always engaged, front axle is part-time. But you'll get slightly better performance with syn in both (I put RP in both axles of my XJ & the Ram came with syn in both).

4. No reason to stick with Pennzoil, but believe Amazon has it.

 

[BigCahuna]

FWI, a while back I needed Gl-4 oil, and the only place I could find it on the shelf was my local NAPA store.,,

 

[yonyon]

Originally Posted By: bullwinkle

2. GM LSD axles usually have a tag that indicates if the axle needs LSD lube, or run your RPO codes in the glove compartment. Or find a slippery surface & punch it!


The slippery surface method won't work. GM likes to use those automatic locking differentials. This will behave as an open diff until there's wheelspin, then it mechanically jams up the spider gears and acts like a spool. It's good for fuel economy, traction, fun around corners, and sometimes cleaning up bits of broken gears. These do not require LSD additive.

 

[901Memphis]

Once again i will recommend Redline gear oils, they are some of the best in the business.

I would use synthetic in both if you can afford it, since the cost is negligible for something changed so infrequently.

http://www.redlineoil.com/product.aspx?pid=133&pcid=4

 

[Rand]

you need gl-5 oil. all common modern truck axles require it.

 

[drolds]

Rand got it right, GL-5 if for differentials. GL-4 is for manual transmissions with yellow-metal synchros. I would go with synthetic GL-5 in both differentials.

The way you can determine if you have a limited slip differential is to:
1. Either find the tag that identifies the exact differential you have or
2. Lift up the the rear of truck and spin one wheel. If the opposite wheel rotates
the opposite direction, you have an open differential. If both wheels turn the same direction when one is spun by hand, you have limited slip, called a "posi" by some people.

One other way to goto the dealer and ask the parts dept. to look up your truck's VIN number. That may also identify the differentials your truck came with.

Dr. Olds