Which Diff and Gear Size for 9 inch

[fordguy]

so i am getting ready to build my 9 inch, (learned the hard way by building my dana first with 4.11s which aint gonna cut it with overdrive). I have an explorer engine (2000) with a comp 266 cam and 4r70w with explorer efi. I like everything i have read on the yukon grizzly, but i will listen to what you guys recommend. I have the tru trac in the front that will be regeared once i get the truck running and decide i like the gear i choose. My goal is to be able to drive to OCBR do some mild trails and come home. My other uses will include mild hunting roads at home and street use. I plan on running 33 inch tires with a 4.88s, i dont know if would be happy with 5.13s, but i know i would not like 4.56s, so i dont think going down numerically is where i want to be. let me here your opinions. The yukon is inline with what i would like to spend.

 

[bronconut73]

33's=4.88
35's=5.13

IMHO


I plan to do a 4R70W in the near future too,

 

[suckerpunched]

What Bronconut said.

I'm getting ready to do mine. similar combination but running 35's I am going with the grizzly and 5.13s

 

[sykanr0ng]

As they have said 4.88 for 33 inch tires.
If there is a move to 35 inch in the future 5.13

Why not a TrueTrac in the rear?

The only thing is they don't work if you have a wheel in front off the ground and a wheel in the rear off the ground at the same time, but if you do that you are not on a mild trail.

 

[fordguy]

As they have said 4.88 for 33 inch tires.
If there is a move to 35 inch in the future 5.13

Why not a TrueTrac in the rear?

The only thing is they don't work if you have a wheel in front off the ground and a wheel in the rear off the ground at the same time, but if you do that you are not on a mild trail.

you have a point, probably has much milder manners? no 35s in the future. i thnk i am going with US gear for the ring and pinion

 

[Skiddy]

getter done for OCBR

 

[fordguy]

getter done for OCBR

long ways from that, but I do hope to attend this year.

 

[Boss Hugg]

You have 51 days...

I wouldn't be afraid of 4.56's for 33's unless you plan on moving really fast. The air tends to be more of a burden on an engine at higher speeds in these things. I decided to go to 5.13 instead of 4.88 (on 35's) because I needed to self-restrain my speed. (And it's better in the rocks!)

For mild trails, True Trac should be ok. And if you did get in the wedged-up situation mentioned above, I've read that you can touch the brake and it'll for the diffs to do their job and keep you moving.

I decided to go with the Grizzly over the true trac because I already had a locker in front, so why not add one in the back and be positively locked. not to mention that the True trac costs almost as much as the Grizzly. But I almost went with the cheap Monkey Grip version of the TT, too.

 

[fordguy]

You have 51 days...

I wouldn't be afraid of 4.56's for 33's unless you plan on moving really fast. The air tends to be more of a burden on an engine at higher speeds in these things. I decided to go to 5.13 instead of 4.88 (on 35's) because I needed to self-restrain my speed. (And it's better in the rocks!)

For mild trails, True Trac should be ok. And if you did get in the wedged-up situation mentioned above, I've read that you can touch the brake and it'll for the diffs to do their job and keep you moving.

I decided to go with the Grizzly over the true trac because I already had a locker in front, so why not add one in the back and be positively locked. not to mention that the True trac costs almost as much as the Grizzly. But I almost went with the cheap Monkey Grip version of the TT, too.

i saw where the trutracs have gone up a bit. how are the street manners for the yukon grizzly? Final ratio with 33s and 4.88s ends less than 3.50ish, so as they say "dont fear the gear

 

[Boss Hugg]

I haven't driven it yet, but people say they're not bad behind an auto. If in a manual truck, they can do crazy things. Now, if you've got a hard shifting auto... you might not like it.

as far as ratio, it all comes down to how fast you want to spin the motor to get where you're going. 33's and 4.88 is going to put you at 28-2900 in OD at around 70 (without running the numbers.)

And i'll add this. The other night, I pulled out of a gas station and gave my explorer setup half throttle. When I hit 3000 rpm, I felt myself sink in the seat a little... I hadn't noticed that in the past, but I DO like it!

 

[sprdv1]

Don't drive it too much on the streets, but running 4.88s with 37s on mine.

if you went w/5.13s for the 35s, you could jump up to 37s as well I'd think

See you in SEPT

 

[sprdv1]

long ways from that, but I do hope to attend this year.

Make it happen.. I'll be at duplex, top of hill walking up to our staging area, do introduce yourself...

 

[Skiddy]

Make it happen.. I'll be at duplex, top of hill walking up to our staging area, do introduce yourself...

will you put the orange cone out for me too

 

[Brent13]

I did a Yukon Grizzly a few months ago, and I swear I rarely notice it on the street. I almost worry that it isn't working properly!!!! It will scrub/chirp the inside tire on a turn, and that is it......

 

[fordguy]

Make it happen.. I'll be at duplex, top of hill walking up to our staging area, do introduce yourself...

will do that

 

[blubuckaroo]

There's actually a way to select the proper gear ratio for highway efficiency.
The hard part is you need to know your engines peak torque RPM. If you have a stock motor, that's easy.
You just select the gear/tire combination that puts your car at that RPM while driving the way you plan to drive.
For most 302s that's about 1800-2000 RPM. For a 351W it's about 1600-1800 RPM.
Of course your engine may be different, and also, you might want to hedge the gear a bit lower since this is an off-road vehicle.
But gear selection is really pretty simple.