4.9 tranny and 4.57 diff gear + 33s

[dank]

Thoughts anyone?

Currently on 31s with 4.9 tranny and 3.7 diffs. I love the current crawl ratio (66:1) but am gonna go up to a 34 (33.6) tyre so am thinking some lower ratio diff gears to even things up a bit on and off road and get a slightly lower crawl ratio.

31 to 34 is 10.54% gain
4.57 diff gears is 22% gain


have searched for prices on Vit 5.12 and it seems that prices range for about 300-500 per diff centre and I can get yukon diff gears from the states in 4.57 or 5.38 for a little cheaper than that as I am ordering in some other stuff.

what are peoples thoughts? Do other vitara ratios fit in sierras?

Could I live with just the 4.9s?

[nicbeer]

u can get a 4.6 ratio vit diff but not sure how common they are.

[Spike_Sierra]

i would say suck it and see.
it depends on what terrain you drive. or alternatively you could sell the 4.9's and go to the 6.5 trail toughs, you would come out about 300 bucks worse off but lower gearing

EDIT: or buy these http://carl.outerlimits4x4.com/viewtopic.php?t=118636

[nicbeer]

arnt u going for 34's now Dank.

5.12's may be the go but not sure how they effect the final ratio.

i may be interested depending on $$ if u sell the 4.9s.

Nic

[dank]

Yeah i am going 34s which measure 33.6. I reckon the 5.12 r&p will make my high range a little low. The 4.9 transfer has a high range reduction of 12 % from memory plus 5.12 drops it to around 35% reduction in high range which will be too low even For 34s. I'm gonna go the yukon gears and as spike said suck it and see. I am concerned that the 6.5s would put too much pressure on drive line to turn 3.7s with 34s. The 4.57s should even things up a bit, and probably give me the equivelent crawl ratio of around a 6.1 transfer and standard diffs.

[Spike_Sierra]

if i recall correctly, theres a guy that runs 34's with just 5.12's, but only said its just better than stock(which isnt anything to write home about)
so i think youve got it spot on with the 4.57's.

gwagensteve should put his head in here, i think hes got 34's and 6.5's.

[Gwagensteve]

gwagensteve should put his head in here, i think hes got 34's and 6.5's.

I'm running 34's with 4.11 1.0 diffs and a Trail tough 6.4:1.

Offroad it was fine with the 3.1:1 1.0 first gear - 81.3 crawl
Now I have the 660 I have a 4.1:1 first - 107: 1 crawl. It's wuite good

On road - 4th gear is still best for cruising but remember I only have a 660. It holds 100 fine. I have no tacho but the novak conversions gearing calculator will give you the answer for revs.

A certain workshop in Vic was anti rockhopper and would only recommend dual transfers and/or 5.12 diffs.

In an otherwise stock car, 5.12 diffs will correct big tyres onroad fine, but only provide a 42:1 crawl which is OK for mud but not suitable for steep country. It also really requires a 1.6 to be drivable, Which the particular workshop also really liked to sell. Not bagging anyone, just pointing out facts.

If you divide tyre size by gearing you get a better idea of actual gearing offroad.

Stock sierra: 33.3:1/26 tyres: 1.28 tyre corrected crawl
Stock sierra, 5.12's, 34's: 1.19 tyre corrected crawl
Stock sierra- 34's, 6.4 Case:- 2.50 tyre corrected crawl.

A stock sierra with 34's and 5.12's is about 10% TALLER GEARED off road than a stock sierra with 26" tyres. With the added traction of bigger tyres, it's not going to work on the steep stuff.

Steve.

[Spike_Sierra]

also this is quite good to think about too
-Gearing Thoughts/Concepts..
Q. Which is better axle gearing or a t-case kit ?
A. While doing transfer case gears is probably the biggest bank for buck and a quick-fix, it is definitely a lousy way to try and create a reliable, trouble-free drivetrain. Think about this for a minute... You put on larger tires. Now your pinion becomes TWICE as hard to turn. This puts TWICE as much stress on the u-joints, the transfer case mounts, the transfer case itself, and the brackets on the side of the frame that holds the transfer case in place. "GEE I wonder why I need these big honkin' driveshafts now"...or "why do my bolts pull out of the transfer case on the long arm side"... or the mounting boss breaks off of the transfer case....or the short arm side bracket starts tearing off of the frame rail. "Gosh - maybe it is because I gave my transfer case almost 3 times as much power by putting in 6:1's and now it wants to do flip flops in its mounts because I must have FORGOT to change the ring and pinions relative to my tire size - which would have made the driveshaft easy to turn again and takes all of the strain off of these parts - like it was made from the factory when the little tires were on it." It is a MISTAKE to do all of your gear reduction at one point. Especially that far up the mechanical chain. Do yourself a favor...reduce the ratio at the ring and pinions relative to the size tire you want to run, then select the transfer case gears that will best meet your 4-wheeling needs. By going this route, you will have a well thought out and trouble-free drivetrain working well within the parameters of strain that the parts can and will reliably handle. -Brent (Trail Tough Products)

[dank]

well the 34s have arrived...thanks MUD EMPIRE! Just gotta get round there to pick them up.

I did read that Trail Tough blurb about a year ago and it definitely influenced my decision to go with 4.9 transfer gearing with 31s whilst knowing somewhere down the track i'd be going looking into the future of going bigger tyres and then changing my R&P to suit. My aim is to build my zook into something reliable and that won't break for under the 10k mark....right now i'm sitting on about 7k and further developments being a 1.6 8v short motor and a rear airlocker for the front when i eventually snap my cvs and replace them with some double toughs....

by the way does anyone want my Silvertone MT-117 Extreme 31x10.5s? PM me. asking 780.

These are the tyres I got...


it'll be interesting to compare them to the MT-117 extremes...