So I have decided to keep my truck for sure. I love it. I cant get the smell of diesel out of my nose. I hope to have it forever. The problem I am having is that I am only getting about 10 mpg and I would like that to go up. From reading on here, and the questions that I have asked before, I know that a good way is to re-gear the rear end. So what I need is a little help figuring out what rear end I have. It looks like a Dana 60 or 70, but maybe yall can help.

Here are a few pics:

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The code on the right tube of the axle says SR22X 4C402-3NA

Can anyone tell me what it is, and what the highest Gear ratio is that I can use?

 

Someone correct me if I am wrong, but I've been told on here that if it has a rear fill plug, its a dana. And it looks just like my d70, but I'm not for sure. Is it SRW or DRW?

 

That is a Dana, you can see the little diamond on the bottom right of the punkin.

The model should be stamped in the housing in one of the other corners.

It looks like a 60.

I see numbers or what looks like numbers under the brake line, top right corner.
If it has a ratio tag, it should be in the dark area, bottom left side.

I also think you have more numbers under the brake line clip.

Looks like the model number is on the top left corner, gets to fuzzy when I enlarge the picture to see what it says for sure, but it looks like a 6 is the first number.

 

It is a SRW. So up near the brake line will be the ratio? What can I do to lower it? Should I just go try and find a Sterling?

 

Do you know the following?

1)transmission
2)axle ratio

if not look up the code on the door sticker to see. I'll take a guess and say C6 auto with 4.10 gears.

You have a few options. If this is indeed a D60, than 3.08s are not an option if you want to keep the whole rear end.

You can look for a D61 which is designed to accomodate 3.08 gears. its possible that this is a D61. I was able to source a complete rear end that had 3.08 gears once at an auto wrecker before I knew that I could get gears for my sterling diffy.

And finally, you can swap to a sterling rear axle as long as it is a 10.25 and not a 10.5. Its very unlikely that you will find one that already has 3.08 gears, but its still worth try. The Sterling is a better axle that is stronger, more modern and easier to work on.

If you can settle for 3.54 gears than you can go with any of these differentials. D60, D61, D70, and sterling 10.25.

 

The transmission is a C6. Is it easy to put in a new rear end? If I find a junker rear end, should I replace the gears anyways?

 

Replacing a whole rear end isn't too bad, but you will be looking new at U bolts and possibly a few brake lines. Only catch is that the only OEM axle that you might find with an 8 bolt hub with 3.07 gears is the dana 61, and I know many of them were a semi-floater which cannot carry as much load as a full floater dana 60. Replacing the gears may not be needed if they are in good shape. If the gears were not abused and maintained properly than they can last indefinately.

I'm a little hesitant to recommend what you should go with without knowing what you use the truck for. I don't to much weight or carry much load in the truck, so 3.08 gears work great for me and I always have the transfer case low range if I'm loaded on a really steep incline. If you need to tow more than 5000lbs consistently, than you may not like the lag that happens at startoff with 3.08s. Empty, the truck is great to drive and quick off the line, but burnouts are not likely.

If you can find a sterling with 3.08 gears than that would be ideal, but I'm not even sure if they exist from factory. If not, you can still get a sterling 10.25" axle assembly and swap the gears yourself before installing the axle in your truck. Expect to pay $250 for aftermarket 3.08 gears, I went with Motive Gear, and so far they have performed perfectly.

 

My truck is a daily driver, and I am trying to keep it that way. I think the heaviest thing I have hauled so far is a washer and dryer.

I do not plan on pulling anything much more than my dad's bayliner every once and a while. If I leave the Dana in and go for 3.54s what kind of rpms am I looking at going 70mph?

 

Close to 2800 RPM....

3.08s would be about 2400 (both assume some slip from the torque converter)

 

Thanks for the help