1972RedNeck

My truck currently has 3.73's and a G360. I am taching ~ 2,075 @ 70 MPH. If I were to change to 3.54's I'd be taching ~ 1,970. With 3.07's I'd be taching ~ 1,710. To me, this seems to ideal. At interstate speeds I'd be at 1,830 RPM.

Does anyone else have this combo? How do you like it?


I have a Dana 60 front axle. Would I have to find a Dana 61 front axle? Will my Dana 70 take 3.07's?

JBradley500

I have the opportunity to swap to 3.07 axles and i don't think i ever will. I think most people get better milage with 4.10's over 3.54's even.. plus with OD and 3.54's my truck doesn't seem to be working hard at all even going 80mph on the highway. Also parts are harder to come by with 3.07's... doesn't seem to be a good option unless you're trying to be different in my opinion.

JQmile

My setup works really good for fuel economy, but you'll basically have to find a wrecked 4wd truck with a 727 trans to get 3.07s for yours. Gonna be tough!

Trebor

I really wish somebody running 3.07's and a 5 speed with factory sized tires would post a video showing the speedometer of how their truck runs around town. My only concern is the 3 to 4 shift in relationship to 25 MPH, 35 MPH & 45 MPH speed limits. I guess I'll eventually find out for myself because my crew project is a 5 speed with 3.07's.

bryson711

I have also switched my axles out for 3.07s with a getrag. I have not drove it much since then I know my spedo is for sure off from the axle change. I need to figure out how the plastic gears in the transfer case work and where to get them

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PapeCAT

Many Class 8 trucks run 3.07/3.08 gears.


They are a great gear set to use whilst towing. In oversize/weight loads it is a bit harder to start the load in first of course. This problem is overcome in some cases if you have 4wd and 4low.

The benefit to having 3.07s is towing in 4th/direct. No parasite drag/heat from the gears and the transmission stays very cool.

I have run 3.07s with a getrag in two of my trucks. I retrofitted a 'rag in my old '89 and also installed a getrag setup and pair of 3.07 axles in my old '72 crew cab. (Running 235/85R16 tyres)

I highly recommend it. It has it's limitations and if you are hauling an overloaded gooseneck of round bails all day locally this setup may not be for you. I found it best on long highway trips with many long grades. You never have to leave 4th gear.

1972RedNeck

I have put a wanted ad on craigslist to see if anything turns up. This is mainly a highway truck. I will occasionally be pulling (heavy when I do). Right now I can get 18 if I drive 65 - 70. Would I be able to get over 21 mpg @ 70 with 3.07's?

Erska

Don't worry about your speedo.

Just get one of these #54RA2 ratio adapters:
http://www.transmissioncenter.net/sp...n_______va.htm

I bought one for mine. It comes between the similar looking stock one and transfer case or vice versa. Just calculate what you need and buy it. Works great!

I have 39" tires and it works perfect!

bryson711

Awesome, that's what I need thanks,

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PapeCAT

21 isn't out of the question at all with 3.07 and the getrag.

25 was my max with the D250 but just under 22 was my max with the W200 Crew and 3.07s.

I found my axles on craigslist. It was an entire 1989 W250 LE with auto sans Motor for 800 bucks. (Nice truck too. Twas a shame the motor was plucked)

longshotranch

I have 3.07's with a getrag it does real good gets about 24 on the highway. I have a dana 61 front. I would like to have your set up since I'm going from a 33in tire to a 38

1972RedNeck

To bad your not a wee bit closer.

Thunderhog

3.07, 727 NON lock up, Gear vendors, runs 75-80 UNLOADED and gets 22-24 mpg (At 8900lbs)
That said, Loaded (24 foot enclosed car trailer and full size car, about 6-8,000 lbs) at 55-60 it is on the edge of too slow (rpm wise) If it had a lock up converter, it would be too slow (again, rpm wise) flat land is fine, much of
a grade means kicking down to no overdrive, or even 2nd with overdrive.

apwatson50

how did you end up with 3.73 ratio?

1972RedNeck

I don't know. They were in the truck when I bought it.