AXLE CODES:

[Captkaos]

Everything that I have for listings on stock tire size for 81-87's state the stock tires is 215/75/15.

[SUX2BU99]

A difference in tire size that much will surely throw the speed off. Mine seems to be off by 20%, reading low.

That's all great info about changing the diff oil. I just bought a new cover and was going to do that myself. Then the parts guy asked me if I had the bed off, which I don't so he tried to sell me a small transfer pump to get the mollasses-like oil into the diff. He said it's a huge pain to fill it by squeezing the bottle. That true?

[Captkaos]

I never had a problem filling them with a tube.  If you have a problem, just slip a hose over the end.

[VileZambonie]

2) The spec decal on the left front innerfenderwell lists these as the "standard tires."

It physically says on the sticker 195/75R15 ?

[Stewart G Griffin]

OK, first off, i was shocked as well, but here's the pudding:



Again, we have to remember that this is a bone stock, spartan custom deluxe, not a silverado.  i have a rubber mat for a carpet and absolutely no headliner.

So, it seems with my truck and many others we basically have a truck with a car drivetrain and i kind of like it that way.

2) About filling the rear diff, if you could give me a few hours/days to get my other pictures up that relate to this topic, i have a few more "interesting" twists.

[Captkaos]

Interesting.  the first letter X = Front tire and Y = rear tire, so it did come with those on all 4 corners.

[Stewart G Griffin]

Yes, occasionally you'll see a pickup with really tiny looking tires with those step-van hubcaps that don't cover the whole wheel---that's what i got.

It would not suprise me if some of these 70's models came with 14's

[Captkaos]

That I know didn't happen, they were 15's the whole time.

[Stewart G Griffin]

Ok, well it sure looks that way---the tires seem so lost in that big fenderwell.

[zieg85]

When growing up living at home I remember the neighbor across the street bought a plain brown truck with the tiny stock tires/wheels with the hubcaps.  I thought it odd to look at with the painted white front bumper, no rear bumper and a real ugly aluminum cap.  My 85 C-20 shows 2 different tires on my truck.  D rated on front and E rated on back.  The 195's back then paired up with the 2.56 was probably borderline anyway. 

[Stewart G Griffin]

........That's all great info about changing the diff oil.................. huge pain to fill it by squeezing the bottle. That true? etc.

Ok, i got my pictures up.  While we're on the subject of rear diffs and changing gear oil and all that, the only thing i could find that resembles a plug to check and fill oil appears to be this pipe-plug thing;  Is this the drain/fill plug?  (fig. a?)  It's a 10 bolt, not a 12 bolt rear if that makes a difference.


Also, what is this tube thing comming out of the rear?  (fig. b?)  There is a plastic plug at the end of it.

[Captkaos]

that is the fill plug, and the tube is the vent tube to vent the diff.

[1976Scottsdale]

Similar deal here.  On my 1987 R-10, the axle comes back reading, "standard ratio".  The other options are 2.56, 3.08, 3.42, and 4.10.  I am assuming I probably have the 2.73 as it is the only one not listed and I run 1450rpm at 72mph in OD.

[Captkaos]

87 it means 2.56

[1976Scottsdale]

Thanks for the fast reply.  I have an 87 shop manual and it could not tell me.  Will 3.42 gears fit on that 2.56 carrier or does it need a different one?  I have the tools and what not to regear one, and I like the overdrive, just like the engine to do more than idle down the interstate.