Hey guys, have asked this loads of times but keep forgetting.
Am thinking of possibly changing my diff ratios on my rig. As I'm running 33" muddies i get a fair loss in power. they are stock now, what would be good to change them to, to get the power back to factory or even better. also would this change my speedo error, or do i have to do that seperatly ? anyone know of any good things for doing that with ?

This is a pretty costly mod to do donw here in Aus but am very tempted as i copped a speeding fine the other day !!!
let me know,
cheers
Dan.

 

Seems that I have read either 4.56 or 4.88. I think with 33s, 4.56 would be like the cruising gear and 4.88 would be power gear. Changing the diff ratio would also take care of the speedo error, as the speedo gears are geared for the proper combination of tire diameter and diff ratio.

 

The cheaper and easier way to do this is swapping in diffs from a junkyard that already have the gears you want or need. New ring and pinion gears and the expert setup and installation they require are around $500 US dollars+or- $50, PER AXLE!! If you do the work yourself using "recycled" parts you can get the ratios you want for $400 or less (USD) for both axles.

I got really lucky and found a rear diff with the electric locker and 4.30 ratio from a '97 4Runner for $300 including 1000 miles shipping. I got a front diff from an '86 4Runner with 4.30s for $95 including shipping. I gained a locker and lower gears for under $400 with junkyard parts. In the process I learned a lot about my truck.

For the 33s you are running I vote for 4.88 ratios. I'm curious if you have a straight front axel or the tortion bar IFS that most of us have.

 

Hey Matt, unfortunatly i have the IFS, have cranked my tbars but am not going to far as i don't have manual hubs and don't want to do any snapping. I am going to look into the diffs, when you did it did it make a big improvement ?????

cheers
Dan.

 

I have 4.88s and I went from a 31 to a 32 and I can tell the difference on hills. However, I can't imagine it would make a big difference with a diesal. My vote is also for 4.88s.

Changing gears and tires will only correct your speedo if you go back to the same effective overall ratio that you had stock, that is, the final drive ratio at the tires.

So, I'm assuming you started with 31s (?) so you went up about 6% in tire size (100*(1-31/33)=6%). So you're gearing has to be adjusted 6% accordingly.

Steve

 

The reason I did this was to get the electric locker. As I was learning about how to do it I learned about the differen't ratios the electric locker came in. They are 4.56, 4.30, and 4.10. I looked around for a while for a 4.56 for a reasonable price and couldn't find any used. Next option is 4.30 which I found for $300.

The benefits of the ratio change are noticable but not specacular. The spectacular part is locking the diff. The spedometer was off by 7% since i'm running 31 inch tires rather than the stock 28 inch tires. 4.10 stock ratio FYI. The 4.30 swap corrected the speedometer and odometer error. The swap also gives me more use of 4th gear on the long steep highway grades my truck sees. The hampsters used to scream at me doing those hills in 3rd at 60 mph with 4.10s. Now they seem happier holding 65ish in 4th on the same hills.

Some pictures of what I did are on my webshots page. Look under the album called "My Mods"

Changing IFS differential.

You can do it, but those nuts and bolts are tight and need to get back on tight. I broke some tools doing this, they were Craftsman so I got new ones for free.