Questiona about changing axle gear and driven gear after getting bigger tires

[Alex8706]

I apologize if this is in the wrong thread. I wasnt sure which one would be more appropriate.

I just got new tires (265/75R/15) replacing my old ones (235/75R/15) on my 92 sport. First, great fit, no rubbing and the open country a/t looks badass on it. I want to change my driven gear to correct my speedometer. Im at a 5.9% (60mph shown 63.5 actual) difference according to a online tire calculator i used. Its not a big deal and its not very noticeable but its cheap and easy so why not. From what i understand a tooth changes it about 5mph so getting one less would make me closer but still one off. So based off of those numbers i would be good to just get one less tooth then what i have on my driven gear right now correct? Or would that make just make it show a higher speed than i am actually going?

Nest question is about the axle gear. Right now i am running the 3.27 (axle code 41). Is there any disadvantage to having that gear with those tires? Seems a little more sluggish really. I am considering getting the 3.73 as i heard it will balance everything out more between power and gas millage. Would i be required to change anything with the front axle also or would it be fine as it is with a 3.73 in the back while using 4wd? Lastly, what parts exactly would i need to buy to convert over to a 3.73 just the ring and pinion? If anyone could direct me to the parts i need that would be great too.

Thanks in advance. Sorry for all the questions might as well do it all in one post.

 

[Mbrooks420]

If you go with a 3.73 in the rear the front will need swapped to the matching 3.73 ratio as well. Often an entire axle from a 2nd gen is swapped in to gain rear disc brakes. Buying a complete rear at a pick-n-pull is usually fairly cheap, and swapping in the complete rear axle isn’t that hard.

I’m not sure the best course of action to replace the front, I’m sure someone else will chime in on that.

 

[Jason94sport]

Search speedo gear you should get some old posts about the different colors each gear should represent. The gears are slightly different in auto's & manuals & also different in where they are located. They should be fine for your 3.27. And yeah anythign bigger then stock will feel sluggish. You'll need a 3.73 gear swap for the D35 front if you go that route. The swap isn't easy, but it's doable if you have the right tools.

 

[CDW6212R]

Those taller tires do need a better gearing in the diff's. I'd start hunting a 3.73 front diff, from a 4WD 91-94. Someone here should have one, but to find one close to you may be tough.

The speedometer is most accurate with 30" tires, the stock 235/75/15's are 29", so those made the speedometer read too fast. Now you have 30.5" tires, much closer to being accurate, but now it's reading a little slow, which gets you tickets if you drive too fast.

I'd wait until you locate better gears in the diff, then deal with the speedometer.

 

[Alex8706]

I think ive bit off more then i can chew. I did the research to make sure i could get the biggest tires with a stock setup but didnt take anything else into consideration. Ill have to save up to get the 3.73 swaps done. Complete axle change seem like the best way to go but its still pretty expensive. Nearest u pull it is about 3 hours away so ill have to give them a call and see what they got. Is an axle swap the best way to go with the front also? Are there special tools needed to switch out the gears without doing the axle swap? Is there any major downside to running 30.5 tires on a 3.27 axle for now? Might be a few months until i can save up and track down what i need.

 

[CDW6212R]

No trouble, the 3.27's just hurt power and fuel mileage at lower speeds.

 

[Alex8706]

No trouble, the 3.27's just hurt power and fuel mileage at lower speeds.

I was under the impression at the least my fuel millage would be better.

 

[CDW6212R]

I was under the impression at the least my fuel millage would be better.

Yes on the highway only, at steady speed. I have a 91 with 3.27's, and my 93 with 3.73's got better fuel mileage on a long 1100 mile trip. Same weight, 4WD, same stock tires. I was driving fast too, not trying to save gas, just typical trip driving.

 

[Jason94sport]

I had 31X10.5's on my 4 door with 3.27's. It was slow to get to 70. For gas millage. I was getting about 200 a tank. I never calculated, but a road trip to TN from me I was stopping every 200-225 miles for gas.

 

[Alex8706]

Yeah im not sure how much mpg i am getting now but with the stock tires i was getting around 320 a tank with mixed highway and city driving.

I called Les Schwab and they said since i havent had the tires for long they would change it out to stock size for free. I might end up doing that. I took it up to some logging roads and the acceleration difference was very noticeable. I just cant afford to get 3.73s put in.