Gear ratio recommendations?
 

I recently drove my truck for the first time with this setup. It has stock 4.8, 4L60E with 3:08 and 275-60-15 on the rear. It is a slug at best. Seems to need to wind way up to get going anywhere. I was thinking of going to 3:73 initially but I found 4:10 stock axle locally that would be a plug and play. Is this too low?
thoughts?

I want better low end power but I'd still like decent mileage at 70MPH.

Re: Gear ratio recommendations?
 

You have the exact same setup as I had on my 65 prior to rebuilding the 72-12 bolt. I chose the 3.73 gears with a posi unit. mine is very responsive AND I still get around 19/20 on the hwy.

Re: Gear ratio recommendations?
 

Clyde,
Thanks for the prompt response. Where did you purchase your posi unit? You remember how much it cost you? I've never set up a gear set, so is this something an average shadetree like myself can handle? thanks

Re: Gear ratio recommendations?
 

My opinion is that a 3.73 is ideal with the overdrive trans. 4.10 would be a little steep but could still work, depending on how anxious you are to make a swap.

It's not rocket science but a person does need to be walked through it once or twice. You'll need to know what's important and how to get there.

K

Re: Gear ratio recommendations?
 

I like the 3:73's for ease of availability in the 12 bolts. They work well with the final ratio's on most of the late model auto's. If you went up to a 6spd, then a steeper gear might still work for ya.

3;73 seems to be good enough for takeoff, but still keeps ya under 3k at 70mph

Re: Gear ratio recommendations?
 

I would go with 3.73s. I've got 4.11's in mine, but I have a 31" tire and an A6.

Re: Gear ratio recommendations?
 

Thanks for all the responses. Does anyone know if a 70 model gear set and carrier will be a direct fit in a 73 up rear diff housing? I have a few extra 6 lug rear ends, I was thinking of just swapping the gears for now until I can save up for a posi unit.

Re: Gear ratio recommendations?
 

Mine has a 3.42:1 in it and while I haven't had any experience with gearing for different applications I have been told that this will be an excellent ratio for the highway with a overdrive transmission with 15" wheels, so we will see what's up when I get her driving and take a road trip.
I want to set mine up as a posi but I have waited because I want to see how it does first before I spend that much money on it.
I also need to find out what will happen to my RPMs if I decide to run 18" wheels and tires before I make a decision.
Here is a Calc so you can figure out what your final gear ratio should be.
http://www.summitracing.com/expertad...tio-calculator
Solving for RPM I found that with a 3.42:1 ratio, 28" tall tire, speed of 75, I would be sitting at 3,078 RPM's.
That's only 1:1 ratio though so I guess this isn't that helpful for us overdrive guys :lol:
Take your RPM x 0.65 to get your final OD RPM's.

Re: Gear ratio recommendations?
 

I'm a long ways from driving my LS C10 but my 2004 chevy 1500 is a 5.3 4L60e with 3.73 gears and when it's on stock tires, it barely turns 2000 RPM at 70 mph. I'd think you could do the 4.10 and be fine. Find the 4L60e final ratio and play with that calculator Xeen posted ^^^
If you skip on the 4.10 rear end I may get the info from you. ??

Re: Gear ratio recommendations?
 

Here's a couple more RPM calculators:

http://www.apexgarage.com/tech/gear_ratios.shtml

http://www.hurst-drivelines.com/?page_id=11

http://www.grimmjeeper.com/gears.html

Re: Gear ratio recommendations?
 

My thoughts...go 3.42 on the gear& a little loser on the verter....OD, & locked up, you will get the milage, but she will "dance' out off the line? Longhorn

Re: Gear ratio recommendations?
 

I have a 5.3/4l60e in my 74 longbed with 3.08 gears. Acceleration is not too bad. The engine runs just under 1600rpm @ 60MPH. Got it up to 91MPH the other day...probably the fastest the truck ever went in its life lol. I wish it had a little more get up and go though. I'm looking into a 3.73 posi rear end as well. I heard 3.55 gears are the best of both worlds though. Im considering that too

Re: Gear ratio recommendations?
 

I'm in the same boat 4.8 4l60e 3.08 gears. Slug in town but sure like the hwy cruise speed. I just shift out of OD while in town works well. I want a posi down the road and will be changing the gears out. Is any one running the 3.55 if so what's your opinion. I'm currently running 27" dia tires but thinking of 20s or 18s in the future.

Re: Gear ratio recommendations?
 

The truck 12-bolt gear ratio is 3.42:1 where as the car 12-bolt gear ratio is 3.55:1.

Re: Gear ratio recommendations?
 

If you set the pinion depth, & back lash RIGHT ON....run the pattern, yes, it will work...longhorn

Re: Gear ratio recommendations?
 

Sorry Mike, I missed this...

I got all of my parts for my rear end from Summit.
The posi I got was ...
http://www.summitracing.com/parts/au...del/c10-pickup

I also got Richmond Gear 3.73:1 rear gear set and master rebuilt kit with new everything.

I had a local tech that works for a trans shop that I trust rebuild a spare housing I bought and stripped, cleaned and painted myself.

I probably have $850 in my rearend rebuild. The tech, shop and I worked a deal to exchange labor. I am a computer tech and they needed some help on shop and personal computers so this saved me money ( also got me a couple new side jobs too!!)

I hope this helps.

I dont hot rod my truck much....but it is very responsive and will lay some rubber when I want to. it also does real well on the hwy.

Re: Gear ratio recommendations?
 

Clyde what's your mileage.

Re: Gear ratio recommendations?
 

mileage? meaning what is my MPG? I have gotten 20.5 once, that was about 75% highway. I usually drive about 25% highway and the rest cruising because I drive it to work 2-3 times a week, I work about 12 miles from home and mostly city driving.

last time I checked, I got 15.5/19.5.