Drain Plug and Differential

[Barra]

I have a couple questions I was hoping for some advice on. THe first is the oil drain plug...I have a 1995 6.5 TD k2500 Suburban. Does anyone know what the specs are on the oil drain plug? I went to replace it the other day (nylon washer fell apart) and the parts store had about 3 choices.

Next question (yes I'm new to the self-maintenance thing) is how do I tell what differential / axle set I have on the truck? I'd like to put auto-lockers in, but I haven't a clue which model differential is on the truck.

Thanks in advance for any help!
Cheers!
Barra

[sturgeon-phish]

In the glovebox is a sticker with a bunch if letter number codes. You can tell your diff ratio using them. A whole list of what the codes are are on link here on DP and do yourself a favor and print them out. I'd guess yours is a GT4 - 3.73, or GT5 - 4.10.

[Barra]

So that would translate to a Dana 41 or Dana 50 or....? Sorry, I'm still a bit lost here, though I do recall seeing the sticker in the glove box (truck's parked in the commuter lot, actually looking it up will have to wait for this evening).

Thanks much!

[diesel1995]

Being a k2500 suburban you're pretty much limited to 2 choices for axle. You could have either a full or semi-floater 14 bolt axle, its very easy to tell the difference a few ways:

1. Count the differential cover bolts in the rear, it should be 14, then look and see if the axle has a bolt on pinion, if it does this would make it a full floater.

2. Remove hubcaps (where neccassary) and look at the end of the axle, if it has a flange with 8 bolts, instead of a "dead hub" like a car would have, its also a full floater, if not, it is a semi floater.

I beleive the front axle in all 3/4 ton diesel trucks was the larger of the two ifs axles (9.2" Ring Gear?) -- this im not sure about, but the rear axle, i know for sure.

Also -- a semi floater 14 bolt has a round shaped diff cover, whereas a full floater has more of an octagon shape to it.

14 Bolt Full Floater -- 10.5 inch ring gear, standard factory gear options (over all years) 3.42, 3.73, 4.10, 4.56

14 Bolt Semi-Floater -- 9.5 inch ring gear, not sure of available ratios

Both of these were available with gov-loc from the factory.

[Bruce Ostien]

Diesel 1995, It sounds like you know somthing about these axles. I have a 1999 3/4 Suburban with a G80 locking rear differential. I believe you were reffering to this locker as a gov-lock. The manual sayes to use GM only: 1052271 new part number: 89021671. This is an API GL-4 80w-90 gear oil ($7.39 /32 oz. container) I would prefer to run a synthetic gear oil (better for cold weather). Can I dump in any synthetic gear oil or will this screw up locker operation?

[moedog]

IF YOU HAVE A JOBBER WHO WILL TALK TO YOU THAT SELLS MOBIL 1 SYNTHETIC GEAR OIL, ASK THEM IF IT MEETS YOUR STANDARDS, THE GOOD ONES WILL KNOW. I RUN THE 75-90W MOBIL 1 FULL SYN. I PUT THREE OUNCES PER QUART OF LUBEGARD ADDITIVE TO THE MOBIL 1 AND FEEL READY FOR ALL THE PULLING AND 4 WHEELING I DO. NEVER HAD ANY TROUBLE YET. ALOT OF GUYS PUT THE LARGER CAPACITY MAGTECH DIFF. COVERS ON TO INCREASE THE AMOUNT OF FLUID AND REDUCE THE CHANGE INTERVALS

[Barra]

Thanks for the help folks. Another question to narrow it down a bit more...I've got the 14 bolt diff...how do I tell 10.5 vs 9.5 without taking it apart and measuring the ring gear?

[ucdavis]

P3 rear is different, so can't help there.
I replaced my drain plug w/a Fram brass valve unit (think I got it from Pep Boys, but I've seen 'em at all big chains) that has a replacement plug, a brass cap, and a screw-on extension hose that drops the empty location about 10". It keeps that annoying last dribble from blowing past the drain pan when I empty, and gives me more point blank aim. Missed the pan by a tiny bit once; what a mess. Anyway, the replacement stub has a copper washer and it is a permanent replacement for the plug. After I drain, I unscrew the tube, screw on the brass cap (nicely knurled) & voila.
Now if I could only eliminate the dribble-over when removing the filter...

[Keith Richards]

Barra, as diesel 95 was getting at,it's pretty easy to tell if you have the full floater"stronger"axle.It has a bigger ring gear10.5 inch.You can see that by looking at the diff cover.It comes to more of a point at the bottom. You can go look under a 1 ton dually or single rear wheel gm truck and see the same axle as you probably have. :

[Barra]

Keith, Diesel 95, Thanks! I should have read D95's post a bit more carefully...thanks for point it out, Keith. Turns out I have the full floater.

Cheers!
barra

[diesel1995]

Bruce, I beleive you would be fine going with any good quality synthetic gear oil (they often go hand in hand). The one concern i do have is that the part number that you gave is basically for a gear oil that comes with a limited slip friction modifier already added from the factory. This causes a few issues: i'm not sure that the gm friction modifier mixes well with synthetic oils, but I have heard somewhere that this is not neccessary when using synthetic oils, but you may wish to consult a gm service center before taking my advice.