Ok, I hope this won't be frowned upon because I have looked around a bit on here and only found an array of varying opinions on tire size:gear ratio. I am running 33x12.50's on my truck with the stock 4.10's, and I have a screaming rear end for the second time in 8 months! So I have an automatic parts truck with 4.30 gears, and I am wondering:

If I change to 4:30's front and rear, can I safely run my 33's??? Or should I switch back to my 31's (I would need to remove the body lift and/or suspension lift in that case).

ALSO, I am going to have the pinion angle checked this week after I swap rears. I have a 4" trailmaster block/bracket lift. I haven't searched yet for the proper pinion angle, but is anyone knows it please save me the time! Or else I am sure I can call the manufacturer at last resort. I just want my Yota to be reliable again. Help!

 

It's got to be something with the pinion angle... I ran 33x12.5's on my stock runner with 4.10's for years with no issues.... Sorry I don't know what the angle should be.

 

Easy enough to check the pinion angle yourself:
- http://www.4crawler.com/4x4/CheapTri...n-Measurements

 

Sub'd on 33's and 4.10 currently.

Can someone clarify what the pinion angle has to do with the gears themselves? I can understand driveline vibrations and/or a hopping feeling but I don't understand gear wear issue due to pinion angle.

 

your truck should be running find with 4.10s and 33s. I did for a few months. It definitely has something to do with your pinion angle.

 

Well, not having the proper pinion angle (matching the t-case angle) causes vibrations in the shaft. That can shake the pinion bearings/flange loose, then that can let the pinion gear move around on the ring gear and throw off the contact at that point leading to increased wear.

 

Ok thanks 4crawler that makes sense, but one would think they would notice the driveline vibration due to a loose pinion flange.

Question is is how long does it take for the flange to loosen and then wear out the pinion bearing and then how long before it toasts the gears. I would think something like that would take more then 8 months as long as the gears were setup correctly from the get go.

I guess it would matter on how the truck is used and how many miles are put on it as well, so this is generally speaking. He's the first one to mention any issues with the 33 / 4.10 combo as far as as longevity is concerned. That I have seen anyway.

 

Easy enough to check the pinion flange. Block the tires, trans in neutral and grab the flange, feel for any play. If play felt, it is loose, unstake the nut and tighten. I just had to snug mine up last week. Usually only feel vibes from a loose pinion flange only when you just back off the gas, when there is slack in the drive shaft.

 

yeah I get that a little as well. Even before the 33's on 31's. I already did the rear t-case still seems a little loose to me even after taking a torque wrench to it, but it might need a new bearing. Have yet to check the rear end though.

 

Thanks for all the replies. I also ran 33's on my '94 Runner for a long time and never had any issues. With this truck I don't wheel very often at all, and it is just mainly DD activity. The pinion shaft seems to be pointing up at a very sharp angle, honestly.. but it probably need to for 4" lift, and it doesn't seem to have much room for error with the blocks.

Unfortunately, tightening the shaft will not help me. I noticed I had a leaking axle seal and drained the diff, thinking I had run it dry and that's what was the cause, but not only was there a lot of oil still in the diff, there was also a lot of metal :| And, never really felt any unusual vibrations... UNTIL I heard her starting to talk to me with the rear slider open. Now she's screaming already.

So the big question is about the 4.30's. Should I bother swapping both front and rear to the 4.30's because I have them? After I do, I will check the pinion angle (if I can figure out what it should be), and also make sure the axle is straight (I'm sure I'd have fealt something if THAT was wrong).

&%*&^(*& lifts! I learned to love Toyotas because of their stock reliability and that they could go anywhere stock. Then I had to get this lifted truck, and... !

 

Leaking seal is often the 2nd stage of a loose pinion shaft/bearing. And metal in the oil is a sure sign as well, pinion bearing will walk up and down the ring gear as load changes, messing with the tooth engagement and generally chewing them up. If you look at the teeth, they'll likely be worn down to sharp points.

Proper pinion angle, assuming a shock rear shaft is as shown below:


The angle (relative to the t-case end) should actually be the same as before the lift.

 

Hmm well my diff points sharply UP.

 

Well, if you have a CV shaft, then that is a good thing, if you have u-joints, it is not a good thing:
- http://www.4crawler.com/4x4/CheapTri...n-Measurements
- http://www.4crawler.com/4x4/CheapTri...n-Measurements

Might be the reason for the multiple rear end failures. A CV shaft may be a good idea.