A rear end question
 

Today I was under my truck cutting out my old rotted muffler...

I tried the "mark the driveshaft and spin the tire" trick to see what gears I have... the drive shaft turned 1.5 times to 1 revolution of the tire. what does that mean? whats my gears

Next question: my axle seems to be aftermarket, here are the numbers next to the cover... CN1 (upside down) K138 on the driver side and L3 stamped on the pass side. what do i have?

thanks

Re: A rear end question
 

I know when I pulled my rearend out I counted each half revolution of the diff to each full revolution of the tire. It came out to a little less than 4 so I think I have a 3.73 and it sounds like yours might be a 3.08 if that is possible. Maybe someone will sound off to confirm.

FYI my rearend was a non posi.

Re: A rear end question
 

Only way to tell ratio by axle numbers is to get the numbers off the top of the axle tube passenger side. takes a little wire brushing to see them but they are there. with those we can tell you what it originally had in it.

Re: A rear end question
 

Mine says right on the glove box sticker "3.73 Gear ratio" or something

Re: A rear end question
 

mine doesn't say it but it has 3.73's. My front axle had a tag on one of the bolts and the back axle will have numbers on the ring gear (but you have to take the diff cover off) never hurts to change oil anyway! Once you have those numbers there is a chart with the teeth count that will answer your question without a guess...

Re: A rear end question
 

On the ring gear look for these numbers,compare the numbers to ones listed below to find ratio.Example:41,11 on the ring gear means 3:73s.

Ratio 2.56:1 - Tooth Combination 41,16
Ratio 2.73:1 - Tooth Combination 41,15
Ratio 3.07:1 - Tooth Combination 43,14
Ratio 3.08:1 - Tooth Combination 40,13
Ratio 3.08:1 - Tooth Combination 37,12
Ratio 3.31:1 - Tooth Combination 43,13
Ratio 3.36:1 - Tooth Combination 37,11
Ratio 3.42:1 - Tooth Combination 41,12
Ratio 3.55:1 - Tooth Combination 39,11
Ratio 3.73:1 - Tooth Combination 41,11
Ratio 4.10:1 - Tooth Combination 41,10
Ratio 4.11:1 - Tooth Combination 37,9

Re: A rear end question
 

with an open diff, don't you need to turn the wheel twice?
That would come out to a 3.07, which is what comes in a small block/auto truck.

Re: A rear end question
 

I'd say you have 3.07 or 3.08. Mine has a little stamped metal tag attached to the lowest bolt that says 41:11 3.73-1 .

Re: A rear end question
 

OK, i'll check tomorrow when i'm back under there and look for these numbers you speak of. i'll even pull the cover off and look in there too. any recomendations on gear lube to fill it back up with and how much does it take??

Re: A rear end question
 

depends on your rear end and diff cover.... 90W gear oil and 2 qts for a stock 12 bolt but confirm that number first.

Re: A rear end question
 

If you have a 3.07, which I have, can you put 3.73 gears in that housing? I was told at a car show by some guys who had the same trucks, that you could not.

Re: A rear end question
 

well this will be interesting. i'll tackle this tomorrow. It has a chrome cover with 12 red bolts

Re: A rear end question
 

drive it around before you empty the oil... better when it a little warm look for chunks of metal in the oil...small shavings are common. I looked in the service manual for capacities and it says "as required"...go figure. Check your operators manual or a haynes manual... good luck. DOn't forget to pick up oil and a new diff seal, little rtv couldn't hurt either

Re: A rear end question
 

torque values on the cover?

Re: A rear end question
 

service manual says 20 ft lbs... like an oil pan drain plug...!

Re: A rear end question
 

Assuming it's a truck 12-bolt rear end, short answer is "No".
However, you can put 3.42's in it.

Reason is 3.73's and numerically higher R&Ps take a different (a #4) carrier while yours (if it's a 3.07) take's a #3 carrier. What you can do is use a ring gear spacer with a 3.73 on your carrier. Another option is buy a "thick" ring and pinon gear set that will do the same thing. These are fine for stock applications but may not be for high performance/racing apps.

Let us know what you find out tomorrow (besides the fact that hypoid gear lube stinks).

Re: A rear end question
 

Don't use straight 90 weight. Get 80/90 gear lube, and if you have the money, get synthetic. 10 times better than the conventional oil.

Re: A rear end question
 

fill it up to the bottom of the fill hole

Re: A rear end question
 

chopper you need to make a drive up to rockford with that truck to talk and compare trucks!! oh and help me too ;)

Re: A rear end question
 

I was gonna say, fill it 'til it starts running out, let run 'til it quits. It's full. BG makes a great synthetic gear lube, look for a shop that carries BG products. I don't think any auto parts stores carry them. Just repair shops.

Re: A rear end question
 

we will have to do that when the weather gets warm and the roads are clean