Regear

tyhuck · January 15, 2013

I wouldnt go with anything higher than a 4.56, and many of the guys on here will tell you that they wouldnt either. I was going to go 4.10 because I was concerned about mileage too, but there are several people that said 4.56 gave them better performance and MPG than the 4.10s. Im gonna go with the 4.56 in mine because I dont like the idea of constantly running 2500 RPM in OD. That would be a happy medium between 4.88 and 4.10.

LongrangeLauber · January 15, 2013

I wouldnt go with anything higher than a 4.56, and many of the guys on here will tell you that they wouldnt either. I was going to go 4.10 because I was concerned about mileage too, but there are several people that said 4.56 gave them better performance and MPG than the 4.10s. Im gonna go with the 4.56 in mine because I dont like the idea of constantly running 2500 RPM in OD. That would be a happy medium between 4.88 and 4.10.

I'm guessing you're running the 4.88's currently? I know at about 70 mph with 3.73's my rpms run a little above 1500. Do you know what kind of rpm's it would run at the same speed with 4.10's?

yukon25008.1 · January 15, 2013

Everything is retuned for tires and gears, yes.

Im debating on going 4:56.. I have 4:10,s now..but am going to run 35/36" tires

With a 5 spd allison I feel ill be ok, the cost is just alot on mine end with an 11.5" ring gear.

What was your original gear ratio?

tyhuck · January 15, 2013

When I said higher, I meant

I'm guessing you're running the 4.88's currently? I know at about 70 mph with 3.73's my rpms run a little above 1500. Do you know what kind of rpm's it would run at the same speed with 4.10's?

No, I only have the factory 3.42 gears at the moment.

Check out this calculator to get an idea of gear ratios and their affect on RPM.

http://www.novak-ada...dge/gearing.htm

When I said higher gear, I mean a smaller number. For exampler, 3.42 is a higher ratio than a 4.10, and a 4.56 is a lower ratio.

Persoanlly, with the 5.3, Ide try to stay around 2200 to ballance power with economy.

blackout07 · January 15, 2013

I'm running 88s with 37s which is appropriate per the generic calculators around. I was running 35sbefore and the truck was a beast...still is but not quite as snappy. Anyway my highway mileage didn't improve much but in town I went up a solid 2 mpg upon regearing. Those charts calculate size...not weight. They don't take into account the added weight of the tires let alone the wheels. They darn sure don't factor towing into the equation. I recommend you look deeper into this issue and check around the other forums, where these topics and the requisite knowledge is more prevalent. I'd say I was recommended 4.88 over 4.56 by 10 to 1. The off road shop being one of them. I'm no expert on this topic but I'm happy with my decision. As far as rpms o, the difference at 70 mph between 56 and 88 is like 200 rpm, which is nothing.

Frogfish · January 15, 2013

I'm running 88s with 37s which is appropriate per the generic calculators around. I was running 35sbefore and the truck was a beast...still is but not quite as snappy. Anyway my highway mileage didn't improve much but in town I went up a solid 2 mpg upon regearing. Those charts calculate size...not weight. They don't take into account the added weight of the tires let alone the wheels. They darn sure don't factor towing into the equation. I recommend you look deeper into this issue and check around the other forums, where these topics and the requisite knowledge is more prevalent. I'd say I was recommended 4.88 over 4.56 by 10 to 1. The off road shop being one of them. I'm no expert on this topic but I'm happy with my decision. As far as rpms o, the difference at 70 mph between 56 and 88 is like 200 rpm, which is nothing.

QFT

LongrangeLauber · January 15, 2013

I also have another question. I got the truck at the dealer now, and was gonna have them do the work since I'll provide the parts. If they regear the rear to lets say 4.11's and I leave the front at 3.73's for maybe 30 miles to get it home, would it be alright, or will I bind something up even though its in 2WD? If I can do that, I can get a front differential from a scrap yard with the stock 4.11/4.10 gears in it and just do a swap at my house.

Cause I know if I buy parts to regear and rebuild the front diff. and have them do it they will charge me what they charge me for the rear end plus another couple hours to pull the diff. and reinstall it after it is done. Would like to get this answered so I know what my options are for getting my truck home.

tyhuck · January 15, 2013

You should be fine in 2wd, but dont ever lock it in like that or your transfer case will become a trotline weight.

tyhuck · January 15, 2013

I'm running 88s with 37s which is appropriate per the generic calculators around. I was running 35sbefore and the truck was a beast...still is but not quite as snappy. Anyway my highway mileage didn't improve much but in town I went up a solid 2 mpg upon regearing. Those charts calculate size...not weight. They don't take into account the added weight of the tires let alone the wheels. They darn sure don't factor towing into the equation. I recommend you look deeper into this issue and check around the other forums, where these topics and the requisite knowledge is more prevalent. I'd say I was recommended 4.88 over 4.56 by 10 to 1. The off road shop being one of them. I'm no expert on this topic but I'm happy with my decision. As far as rpms o, the difference at 70 mph between 56 and 88 is like 200 rpm, which is nothing.

I didnt realise you were running 88s. Does your truck have the 4 or 6 speed?

My thoughts were that on stock tires, a 3.73 gear suites me fine for what I do. Adding the 35" tire into the equation, to acheivethe same RPM, I would put 4.10s in. But since the tires were also heavier, I figured the 56s would make upt for that without having the engine scream all the time, since most of my driving is 70-75. What kind of mileage did you see with the 35s?

I dont want a dragster, but I do want her to be able to move out of her own way. The 3.42s I have now dont really bother me except for the fact that it will downshift at the slightest incline. She holds 60 pretty good, but 70 is a chore. When towing I just run 3rd gear which gives me a mechanical equivalent of 4.88s, which tows really well, but runs more RPM than Im comfortable running all the time. Maybe Im too old school and too used to the old SBC.

LongrangeLauber · January 15, 2013

So just talked to the shop foreman and he was saying that 4.10's may not fit the differential casing and that the inside diameter of the ring may not fit the posi unit. I don't really believe him, cause I'm sure there are plenty of guys on here with a 10 bolt rear main running aftermarket 4.10 gears.

And I'm sure Randy's ring and pinion would know if I had to change anything. I was thinkn of going Yukon gears cause of their warranty. Anyone have success with these brand of gears?

blackout07 · January 15, 2013

Umm yeah they'll fit fine, if anything you'll need new carriers. Go to a different shop!

Z71 i was getting 14 in town but I was running large 35s and 20 x 10s. And that was optimal driving. Oh it's a 4 spd

tyhuck · January 15, 2013

Z71 i was getting 14 in town but I was running large 35s and 20 x 10s. And that was optimal driving. Oh it's a 4 spd

did you do the regear when you went with bigger tires or did you ever run stock gearing?

I can get a consistent 14.5, but Im wondering if it will go up or down with the 4.56 gears on the highway.

blackout07 · January 15, 2013

I ran the stock gears for years and got 11-12 mpg. But I'm rocking 10" of lift and a much heavier set of wheels/tires.

LongrangeLauber · January 15, 2013

Umm yeah they'll fit fine, if anything you'll need new carriers. Go to a different shop!

Z71 i was getting 14 in town but I was running large 35s and 20 x 10s. And that was optimal driving. Oh it's a 4 spd

I was going to buy a Yukon posi unit for the rebuild anyways, so I'm sure their own ring will fit their own posi