3.42 or 3.73, opinions please

[USSkoval]

I am currently looking at putting a 6 lug 14bolt rear in my mostly stock '77 Blazer that has 3.08 gearing. A local yard that delivers to my work has a 3.42 and a 3.73 4x4 axle in stock. My Blazer only has 33's and sees a lot of highway use, so I'm thinking the 3.42 axle would be a better choice for me. I also have a 3.42 axle I could put in the front. I don't plan on running a bigger tire, but I do plan on swapping in my aluminum headed 350 out of my Camaro. Am I correct in thinking the 3.42 would be best?

Also, the 6lug 14bolt 4x4 axle is the one to swap in, rather than the 2wd axle, correct?

 

[sweetk30]

3.73 much more popular.

hare bit wider than 2wd axle.

 

[4X4HIGH]

If it were me i would go for the 3.73 geared axle, however if you already have a front axle with 3.42's that would avoid having to do a gear install up front which could lead to some coin. I'm guessing the front axle you have must be a 10 bolt since i'm not seeing a 3.42 gear as being available in a D44 axle.

 

[USSkoval]

If it were me i would go for the 3.73 geared axle, however if you already have a front axle with 3.42's that would avoid having to do a gear install up front which could lead to some coin. I'm guessing the front axle you have must be a 10 bolt since i'm not seeing a 3.42 gear as being available in a D44 axle.

Yeah, it's a 10 bolt now and the 3.42 front 10bolt is out of my '88 Suburban originally.

The current 350 makes great midrange power and so does the replacement... just more of it.

 

[resurrected_jimmy]

Personally i couldn't justify swapping an axle for 3.42 gears. My burb was very happy with 33s and 3.73s (except OD was useless)

 

[tRustyK5]

I think 3.42's would be about right. Get's your cruise rpm at ~2300 at 65 mph which is decent. Both the 77's in your sig say TH350, so that's what I went by...

Rene

 

[BLIDVL]

If it were my choice for a mostly highway truck with a three speed auto I'd run the 3.42 gears.

 

[76zimmer]

If it were my choice for a mostly highway truck with a three speed auto I'd run the 3.42 gears.

as above x3....3.42 with a 1:1 final drive would be good with 33" tires, and highway speeds.

 

[USSkoval]

I'm sure the 3.73 is a better option for power, but like I said, it does see a lot of open highway. And correct, it's a th350 tranny. Both axles are the same price, but the 3.42 only has around 100K on it, while the 3.73 is well over 200K.

Plus I already have a 3.42 front to toss in the truck. I just wanted to get the opinions of others before I spent the money. Thanks

 

[owenst7]

I'd run the 3.42s unless you're going to eventually have an overdrive. My poorly tuned 76 350 ran 35"s and 3.73s just fine. It's not like any of these motors are condusive to those with lead feet anyways.

 

[chulisohombre]

373 was not too bad on the highway.around 2500 rpm.but if you dont wheel it too much and already have the front axle,go with the 342.with 33s being the biggest tire youll run it will be good mid range gearing.