3.42 gears ??

[qadeem]

How is everyone doing....

I have a 1977 Chevy dually truck with 4.10 gear ratio.. boy that truck drinks lots of gas. is it possible to replace the gears to 3.42?

(even though its a dually!!!)

I dont load nor tow with it, only as a daily use. So do they fit exactly with no issues? I dont know about their prices!! I found on ebay Motive Gear for $207... and GM Chevy Rearend for about $150 (360101798980)

have no idea about prices or brands. GM, Motive, or Richmond??. the truck is stock with no modification whatsoever.

waiting for you gentlemen.

[Nin92]

I am assuming that it is a 14 Bolt rear end. I did a quick google search and came up with a pretty wide variety of Gear sets.
Here are some 3.42 sets:
http://www.overstockdiffparts.com/Pr...px?ProdID=7841
http://www.drivetrainshop.com/Yukon_...0gm14t-342.htm
As to what brand to choose, I can't really give advise as to which is superior. Hopefully someone who has some first hand experience will come forward.

[powerdriver 1958]

betting its a dana 70, at least the 79 rear end in mine is

[Nin92]

You can tell the difference between the Dana and 14 by the Differential cover.
Left is a Dana 70. Right is a corporate 14 10.5". If It's a cab and chassis model then I'm 99% sure its a 14 Bolt. But Powerdriver is probably right that it is a 70.

[powerdriver 1958]

wish mine was a 14 . the 4:10s are too deep

[RPOZ11]

3:42.1 gears are still available.
I contacted Tom's Differentials and I believe he is supplying US Gear 3:42.1 ring & pinions for the GM corporate 14-Bolt rear axle.
I will buy a set of these soon as I believe US Gear & others don't find enuff demand to make the 3:21.1 gear sets.
I plan on adding my Gear Vendor with these 3:42 gears to obtain my desired drivability and needed gas mileage improvement!
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[qadeem]

Nin92, powerdriver 1958, and PROZ11, thanks for your cooperation.

Nin92, ya, after seeing the pics you uploaded now I'm pretty sure mine is a DANA 70, which is the left picture. SO SO DEEEP!!

[qadeem]

Originally Posted by RPOZ11

3:42.1 gears are still available.
I contacted Tom's Differentials and I believe he is supplying US Gear 3:42.1 ring & pinions for the GM corporate 14-Bolt rear axle.
I will buy a set of these soon as I believe US Gear & others don't find enuff demand to make the 3:21.1 gear sets.
I plan on adding my Gear Vendor with these 3:42 gears to obtain my desired drivability and needed gas mileage improvement!
Posted via Mobile Device

Thanks a lot.

I went through Tom's Differentials catalog and I saw a 3:73 gear ration on (DANA 70). I will contact them this week for more info. about the 3:42 and DANA 70..

To be honest, I didn't know about the 3:21.1 gear. The problem I'm facing here is that almost all of the 3:42 gears I've seen are 14-bolt rear axle, while the DANA 70 I have is 10-bolt rear axle and has a different diagram. Would I be able switching to 3:42 gears easily with no issues?? Do you know anyone tried to swap a 3:42 in a 10-bolt rear end?

Another thing I'm confused about is that I have another Dually truck with manual transmission, so is it the same rear end as the automatic? I'm just wondering if the Low Granny would make any difference!

[Edahall]

Originally Posted by qadeem

Another thing I'm confused about is that I have another Dually truck with manual transmission, so is it the same rear end as the automatic? I'm just wondering if the Low Granny would make any difference!

Whether the truck is manual or automatic has no correlation with rear ends.

For best fuel economy, 3.08's would do even better. Many Dodge trucks made in the late 80's were equipped this way.

[v30crewcab]

probably no 3.42 for the d70, but you can get a 3.54 from a ford rear for it. I know the dodge 3.08 fronts were a different animal, not sure on the rearends.

[Corts60]

If you are going with a gear vendors unit as well as the 3:42 then that will make your final drive ratio a 2:67 in overdrive. This is the exact set up I run and I really enjoy the good mpg's. I wouldn't go any lower than 3:42 if you ever plan to tow anything.
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[qadeem]

Thank you all. I think I'm going with the 3:42, in case I needed to tow something a day. 3.08 is way better in mpg indeed but I'll try to keep my self in between. I'm contacting Tom's Differentials hopefully today to see how it will fit on the 10-bolt rear axle.

[Edahall]

Originally Posted by qadeem

Thank you all. I think I'm going with the 3:42, in case I needed to tow something a day. 3.08 is way better in mpg indeed but I'll try to keep my self in between. I'm contacting Tom's Differentials hopefully today to see how it will fit on the 10-bolt rear axle.

What engine is under the hood? And how much weight do you plan to tow? I've got a 1982 Chevy Suburban with the 6.2L diesel with 3.08 gears and it pulls my 26 ft Airstream just fine. I do have to downshift to 2nd gear on the hills but it'll pull 60 mph in 2nd gear. Power would be comparable to a very healthy 350 or possibly 400 small block. If you've got a 454 under the hood, it'll love 3.08's.

[qadeem]

Originally Posted by Edahall

What engine is under the hood? And how much weight do you plan to tow? I've got a 1982 Chevy Suburban with the 6.2L diesel with 3.08 gears and it pulls my 26 ft Airstream just fine. I do have to downshift to 2nd gear on the hills but it'll pull 60 mph in 2nd gear. Power would be comparable to a very healthy 350 or possibly 400 small block. If you've got a 454 under the hood, it'll love 3.08's.

I have the 454 in it. I am waaaay far to pull something like the 26 ft Airstream. I may tow a PJ trailer every 8 -10 months (ONES). From your experience with the 3.08 and the 26 ft Airstream, I think that is what I want. I'm giving the truck to my father and he's not pulling anything at all. I'm the one who's pulling a trailer ones every couple months on a "flat road" 3.08 with 400 AUTO fits for me I feel.

[Edahall]

Originally Posted by qadeem

I have the 454 in it. I am waaaay far to pull something like the 26 ft Airstream. I may tow a PJ trailer every 8 -10 months (ONES). From your experience with the 3.08 and the 26 ft Airstream, I think that is what I want. I'm giving the truck to my father and he's not pulling anything at all. I'm the one who's pulling a trailer ones every couple months on a "flat road" 3.08 with 400 AUTO fits for me I feel.

Your 454 should have quite a bit more power / low rpm torque than my 6.2L diesel so it'll still pull alright with 3.08's. My guess is that it'll pull 6-7k and maybe even a little more than that on "flat road". With a heavy load, you'll have to downshift more but as I said, it'll still go 60-65 mph in 2nd gear. You just won't have as much performance in 3rd gear.

Another thing that would help out with fuel economy would be a torque converter for your TH400 with a lower stall rpm. The TH400 was never offered with a lock up torque converter but you still can get rid of a lot of that slip with a different torque converter. Here's an example of a torque converter with a stall of 1000 rpm's.
http://www.summitracing.com/parts/HUP-GM5XFM-1/
This is a common modification on the older 1st generation Dodge Cummins that did not come with lock up torque converters. It's one of the best things you can do on this truck.

[qadeem]

Edahall, thank you so much. I'll follow your advice and i'll update the thread as soon as i install the bears with the convertor. Thanks, qadeem