which gears

[tonkadave]

OK here's the run down.. I'm running with a chevy 350 engine and TH350 auto trany matted to a Dana300 t-case with full size chevy blazer axles D44 front and GM 12 bolt rear with stock 3.73 raito, and 35in. tires. I been wanting to swap in some 4.10/4.11 gears This is my DD also and my gas milage isn't the greatest right now anyway like 8-10 MPG. but back to the question should I go with 4.10 or 4.56's?

[Tazdevil]

I would go with the 4.56 I am running the 4.10 now and will probably go to 4.88. The milage will not be that much better with 4.10. Just my thoughts.

[igofshn]

With an auto, I would go 4.10. Rpm's will be way too high with 4.56's. I run 4.10's with my 3 speed auto and it turn 3000 at 70.

[Guest]

I would think about leaving the 3.73:1's in the pumpkins, and going with a Teralow-300 4.0:1 gear set in the transfer case. That way it will remain decent as a daily driver, and give you some creepy gearing for wheeling...

[DrewTJ]

I had stock 3:73s and just went to 4:56s it is now perfect for driving around town and I finally got 5th gear back on the highway, along with MUCH better gas mileage.

IMO going from 3:73 to 4:10 is not gonna do it, % wise it is negligable, its a waiste of money to go with any higher gearing than 4:56s. I wish I had gone 48s even and I only run 33s. Just my .02

[tonkadave]

Hey drew are you running a manual or auto? Because with an auto. the torque converter is a multiplier. I had a friend who was running 5.13 with his 5 speed and 35 in. tires he suffered on the hwy but excelled off road.

[DrewTJ]

That's a point, I am driving a stick. However, unless you are driving highway daily I would still go lower gearing. Again percentage wise it just seems like a waist to go from 3:73 to 4:10s.
In 4th gear at 65 I'm at about 2400 RPM, so I still say err toward lower gears IMHO.

[Trailbst]

Here is my opinion, for what it is worth.

Go to someplace like Dirtroad.com or Randys Ring & Pinion. Use one of the calculators to find the right gear to match the RPM that you want.

We can sit here and speculate for weeks. If you use the calculator, it will want to know your tranny gear ratio, your t-case gear ratio, the MPH you want to travel at, and the RPM that you want to be at for that speed. Then it will do it's magic and let you know what is the correct gear ratio for your setup. I honestly don't think any of us have the exact combination of driveline components that you do, so we can't honestly answer which is the best for your rig. Although we will give it one heck of a try.


erik

[igofshn]

Originally posted by Trailbst
Here is my opinion, for what it is worth.

Go to someplace like Dirtroad.com or Randys Ring & Pinion. Use one of the calculators to find the right gear to match the RPM that you want.

We can sit here and speculate for weeks. If you use the calculator, it will want to know your tranny gear ratio, your t-case gear ratio, the MPH you want to travel at, and the RPM that you want to be at for that speed. Then it will do it's magic and let you know what is the correct gear ratio for your setup. I honestly don't think any of us have the exact combination of driveline components that you do, so we can't honestly answer which is the best for your rig. Although we will give it one heck of a try.


erik

Those things don't work for automatics....

[Guest]

CHOICES ,CHOICES ,CHOICES

Well running a V8 , you have an advantage over the average jeeper . You have the power to leave in the 3:73s and yes a 4:1 gearbox would get you where you want to be in 4wd , 4:10's would be a slight power increase they are not that far away from the 3:73's to make "a world of difference " . 4:56's would be the difference you would really feel . keep in mind that a 3:73 is ALOT stronger than a 4:56 gear and with the v8 you will have the power to break gears . MY personal opinon would be to go with a 4:10 gear set . you will gain a LITTLE mileage increase and a Little power increase without compromising strength . :confused:

[tonkadave]

Thanks for all the imput. Right now with the 3.73 I'm turning like 2800 to 3000 RPM at 65 MPH. It moves along just fine except for the long hills I lose all of my speed and power unless I drop it down into 2nd. I could be going 85 at 3700 RPM and slow all the way down to 55 at 2500 RPM hills like Cajon Pass on the I-15 I know that a Big hill but really should drop that much???

[Trailbst]

Originally posted by igofshn
Those things don't work for automatics....

Ok, so we've had this conversation before. I am converted about Autos offroad, and the ability to use the torque converter for limited amounts of time to provide infinite:1 Final gearing.

For the road, you still have a overdrive, and you should really be beyond that slippage point for the torque converter, Why won't it work????

Erik

[goodtimes]

Originally posted by tonkadave
Thanks for all the imput. Right now with the 3.73 I'm turning like 2800 to 3000 RPM at 65 MPH. It moves along just fine except for the long hills I lose all of my speed and power unless I drop it down into 2nd. I could be going 85 at 3700 RPM and slow all the way down to 55 at 2500 RPM hills like Cajon Pass on the I-15 I know that a Big hill but really should drop that much???

If you are losing that much speed on little hills like Cajone Pass, you really should be looking at that engine. You should have no problem holding what ever speed you want with a small block, 3.73's and 35's on a light jeep. When is the last time you checked the compression? Timing chain? Tune up?

I would check that out before I spent a LOT of money on gears. Are you sure about those 3.73's? :confused: Your engine is spinning pretty fast (3K @ 65mph). My truck spins less than that with 4.10's and 33's (keep in mind that both your jeep and my truck have 1:1 hi gear in the tranny and t-case, so with deeper gears and shorter tires, my engine should be spinning faster than yours at any speed, assuming we were both in high gear).

[tonkadave]

I rebuilt the engine in early 2000 had the heads done too. I have gears for timing and all that was done at the same time. I have LOTS of power and low end grunt it's the top end that suffering??? I'm gonna be putting in fuel injection soon getting a TPI off a carmero complete with wireing harness computer ect. The only other thing I can think of is why the RPM are high is my t-case it came out of my 81 CJ-7 which came with 151 iron duke 4 banger. I taked with a tech person at fourwheeler mag. way back in 1995 and he said something about differnt gears in that t-case because of the 4 banger???? dont know how true it is but even when I was running the SR4 4speed trany that came stock with the CJ I was always turning high RPMs like 3200 at 65 mph?????? Oh right now I have A Holly truck avenger carb with a Weiand action plus duel plane intake, edelbrok performer-plus cam (for the gear heads) lift at cam intake .280, exhaust .295 block hugger headers 2 1/4 exhaust with flomasters. the trany has a TCI high torque towing converter. ( I grenaded 2 stock one before) and the trany was just rebuilt a like 18 months ago. I did one of those formuals for the right gear combo with tire size ect and it came out to 4.27 gears.

[DrewTJ]

4:56s 4:56s 4:56s [COLOR=red]4:56s[/COLOR] 4:56s