Question on Differential handling with bigger tires

[ZR2]

Hey awesome people,

I’m planning to put 35 inch tires on my 23 ZR2 and i see lots of you done that and even 37s. However, i was just with a friend who owns an FJ Cruiser and told me be careful as your differential could be low ratio and the big tires will break it.

I’m no expert and im heavy off roader going on sand and sand dunning ..etc

My question is, Can my non-HD Silverado ZR2 differential handle 35 inch tires?

Would love to hear your thoughts and maybe you will laugh at my question, eaither response is welcome form you guys

 

[scubatech]

Hey awesome people,

I’m planning to put 35 inch tires on my 23 ZR2 and i see lots of you done that and even 37s. However, i was just with a friend who owns an FJ Cruiser and told me be careful as your differential could be low ratio and the big tires will break it.

I’m no expert and im heavy off roader going on sand and sand dunning ..etc

My question is, Can my non-HD Silverado ZR2 differential handle 35 inch tires?

Would love to hear your thoughts and maybe you will laugh at my question, eaither response is welcome form you guys

He is right. These trucks are geared at 3.23 or so if I remember correctly. There are a lot of gear / tire size charts on different sites, like Discount tire. I would think that 35" tires would put you around a 3.08 / 3.00 gear ratio. Pretty much Impala gears, LOL. Truck used to have at least a 3.73 gear set. I imagine if you are at a lower elevation and with the torque of the 6.2 Liter, you can do it OK. Towing though....I'm not so sure? You have a lot of transmission gears to choose from so it depends on your tastes, I guess. I used to build gears and I would want at least a 3.73 ratio. Keep an eye on your transmission temperate for sure.

 

[ZR2]

Thanks buddy for taking the time to explain this. I’m a bit disappointed then. Below is the calculation i got.

 

[scubatech]

If you have a 3.55 gear that helps a lot. My truck had a 3.23 ratio, I think. You can correct the gear ratio by changing it to say a 4.10, but you still have a larger rolling resistance to over come. I don't think GM offers a 3.90 ratio for their rear end.

I had a JK Wrangler that I put a 392 CI Hemi in back in 2014. I had a 4.10 rear and ran a 315/75/17 tire on it. The tire actually measured 34.3 inches on the Jeep. Here in the high altitude of Colorado on the passes which often were 11000 Feet and a .82 Overdrive I could feel it. I had a 5 speed automatic. A 4.56 ratio would have been perfect but a lot of labor time and 1k in parts, I left it alone. Hell, with 475 HP & 475 torque I would just put it in 4th ( 1:1), and I could easily go as fast as I wanted over these passes. The independent front axle in the ZR2 requires a lot more labor than the back differential. I imagine with todays prices you'd be looking at 2K for labor.

My friend has a JL with a 392 Ci and he was running 37" tires with an 8 speed auto, and he liked it. The Jeep would pull the passes in 5th or 6th. He then went to 38" tires and 4.56 gears and it is much better, according to him. I haven't ridden in it since he went to 38's. So he is happy.

I expect my vehicles to pull any mountain in my direct gear which is 7th in these trucks or I'm changing the gears. That's me though coming from the 60's drag racing days. Vehicles today have more Hp and more transmission gears to play with. There will be some guys on here chiming in that run larger tires when they see your thread.

 

[ZR2]

Thanks for the detailed response my man. Unfortunately its as you said 3.23

 

[amateurhour]

Unfortunately I don’t think there are not any gear sets available for our trucks. Factory ratios are all there is. The max trailering package gets 3.73 but that’s not available on the zr2. Not the most ideal but there’s nothing to be done.
The upside is that numerically lower ratios are slightly stronger as the pinion gear is larger and will have more contact with the ring gear.

With three overdrive gears I would love some 4:10s but until something is available and we’re able to calibrate for it I’m not going to worry about it.

 

[AXE]

I run 295 70 R18 Toyo RT TRAILS ON 9 in wide -12 offset wheels that sit about 34.5 inches. You'll have to trim. I don't think gearing was affected much. Especially if you use manual gears and select off road or terrain mode. Same goes for tow haul mode. I offroad a lot, some in rough terrain, but I'm not rock crawling. I've pulled out two 2500HDs and didn't even break a sweat with the lockers on. I don't think 35s will make much difference, except they are hard to fit in front wheel wells.

I bitch about about unnecessary electronics and associated problems, but there is some magic to it with the 10 speed transmission and all the mode settings.

 

[ZR2]

I run 295 70 R18 Toyo RT TRAILS ON 9 in wide -12 offset wheels that sit about 34.5 inches. You'll have to trim. I don't think gearing was affected much. Especially if you use manual gears and select off road or terrain mode. Same goes for tow haul mode. I offroaf a lot, some in rough terrain, but I'm not rock crawling. I've pulled out two 2500HDs and didn't even break a sweat with the lockers on. I don't think 35s will make much difference, except they are hard to fit in front wheel wells.

I bitch about about unnecessary electronics and associated problems, but there is some magic to it with the 10 speed transmission and all the mode settings.

Thank you my man, all your responses are positive there’s no “no can do” with you. Salute

 

[AXE]

Also, those Toyos are pretty heavy 10 ply rated, load range E. I can easily light them up in L1 and L2. A little harder in D, but can do it it if I stab it! I don't think there's much to be worried about with the 6.2L and 10 speed.

295s on a 20 inch rim are 35 inches tall in the Toyos.

A lot of people sleep on the 295s cause they are focused on 35s. But 295s have a higher ply rating and and load range. So if you're offroading you can drop pressure to 25 psi and still run 40 mph. It rides like you're on glass. A lot of people ask me how i can run so fast on rough roads...... easy, get good tires and drop 15-20 psi. I've run 12 psi in the sand running 23k gross on my 2500HD towing my toyhauler, just not high speed.