What gear ratio should i go with?

[sir_talk_alot]

I wanted to get opinions. I have a 94 ext cab z71. 6in lift, 20" rockstars with 35s. Truck has a good running 350. P.o said he thought that the motor was possibly bored over. I have shorty headers im fixing to run. I found the original sales receipt and the truck was equipped with 373s. I just had the trans built completely through. My buddy did it, said it could hold up to 700hp. I made sure to have it built bullet proof for having fun. Its just a weekend truck for cruising and playing offroad. I may get a small cam, chip and maybe do some head work. Should I leave the 373s or go lower?

[OJ1988]

What Cam, converter and trannny?

[sir_talk_alot]

Originally Posted by OJ1988

What Cam, converter and trannny?

4l60e with a vette converter 2075rpm. Right now itll be a stock cam. The truck has some decent moving power but id like to take some strain off the trans for towing or mud flingin if need be and without making the truck a gas hog on the interstate.

[sir_talk_alot]

Everything is new inside it. Planetary gears improved sunshell zpack wide band new drum etc etc. i didnt cheap out.

[OJ1988]

IMO, cam choice will dictate gears, as well as usage of course.

[sir_talk_alot]

Thinking possibly the isky 256 1500- like 4500 i believe or 262 cam because its 2000-5500. Id like to have alittle more stump pulling power in her. This is my first 4x4

[b454rat]

4:10s at least, maybe even 4:56s....

[mud.man.rj]

Ok, your only running a 35" tire and already have a 4spd with a low first, so stay with 3.73's or 4.10's at the most. Overall I would stick with the 3.73's price wise, because that is 2 diff's and cost double, might as well put the $ into the engine to give it some grunt instead, cause that is not a Hp engine. so a better cam, a 262 or 268 Comp with roller rocker arms will help, can upgrade the intake, stock sucks, a better sized exh, 2.5" duals with better mufflers and can upgrade the stock cat if high mileage cause it will be a cork. headers are a plus. I run 3.73's with a 40" tire with a big block, torque helps of course but gives you a better idea. If running an auto can always run a higher stall as a last addition if the rest isn't quite enough. One more item is to upgrade the ignition, I usually do it last but still helps.

[mud.man.rj]

Sorry, missed the vette convertor post, cool good add on.

[sir_talk_alot]

Yea ive delete cat. 2.5 exhaust and headers. Probably going to find a better intake soon

[devind]

Originally Posted by b454rat

4:10s at least, maybe even 4:56s....

2nd this

I build a lot of axles for rock crawling and Jeep guys around this area.

35" tires need a least 4.1 but in may opinion 4.56 would be a better choice.

[sir_talk_alot]

Originally Posted by devind

2nd this

I build a lot of axles for rock crawling and Jeep guys around this area.

35" tires need a least 4.1 but in may opinion 4.56 would be a better choice.

What am i looking at work wise and price wise to go 4.1? Is it gonna effect interstate driving with 456s or 4.1? Im installing 6x5.5 to 5x4.5 billet 2pc adapters on my truck now to allow me to run the rockstars. Just want to make sure im not gonna have any problems.

[devind]

Originally Posted by sir_talk_alot

What am i looking at work wise and price wise to go 4.1? Is it gonna effect interstate driving with 456s or 4.1? Im installing 6x5.5 to 5x4.5 billet 2pc adapters on my truck now to allow me to run the rockstars. Just want to make sure im not gonna have any problems.

The fact that you have gone with 35" tires is going to affect your interstate driving. That is the reason you need lower gears to compensate for the taller tires. You need to try and get the engine rpm to mph ratio back as close to it was with the stock tires and lower gears are how you accomplish this.

I may be misunderstanding your question but I don't know how the wheel adapter have anything to do with the gear ratio.

Check this link out it is a gear ratio calculator. You can play around with it and see how different gear ratios and tire sizes will affect the rpm to mph ratio.
http://www.ringpinion.com/calculators/Calc_RPM.aspx

[sir_talk_alot]

Originally Posted by devind

The fact that you have gone with 35" tires is going to affect your interstate driving. That is the reason you need lower gears to compensate for the taller tires. You need to try and get the engine rpm to mph ratio back as close to it was with the stock tires and lower gears are how you accomplish this.

I may be misunderstanding your question but I don't know how the wheel adapter have anything to do with the gear ratio.

Check this link out it is a gear ratio calculator. You can play around with it and see how different gear ratios and tire sizes will affect the rpm to mph ratio.
http://www.ringpinion.com/calculators/Calc_RPM.aspx

What all does it take to swap 456s? Jegs has a ring and pinion set for a bit over 200. I dont know what all i need to swap

[OJ1988]

You need a couple hundred dollars worth of specialty tools to properly do a ring and pinion swap.

Most shops charge anywhere from $200-$500 labor per axle to swap.

If you don't set them up properly you can ruin the gears pretty quickly.

[beckmand78]

4.56 or 4.88

I'd go 4.56, been there done that. if you're not comfortable doing the swap, have a professional do it.

[mud.man.rj]

Swapping gears isn't for the faint of heart, need skill as mentioned or a big waste of money and time, still I would go 4.10 not 4.56 especially with highway use, you will not be impressed with 4.56 and will want to swap to 4.10. Have build mudracers and street 4x4's, small and huge for 30 years, just trying make it useful and practical, it's not in the mud all day so lower is not better.

[sir_talk_alot]

Originally Posted by mud.man.rj

Swapping gears isn't for the faint of heart, need skill as mentioned or a big waste of money and time, still I would go 4.10 not 4.56 especially with highway use, you will not be impressed with 4.56 and will want to swap to 4.10. Have build mudracers and street 4x4's, small and huge for 30 years, just trying make it useful and practical, it's not in the mud all day so lower is not better.

This is what i was hoping to hear. How much difference will i feel going 373 to 410?

[mud.man.rj]

Going from 3.73 to 4.10 is a bit of difference around town but not a substancial difference, especially for the $ spent. Like I mentioned earlier I run a 40" tire with 3.73's and a big block, so sure more power from the big block but the tires take up the difference and I run about 2,300 rpm @ 60mph highway with a 4spd manual, so yours being a 4spd auto and having the other top gear should be comparable with the 35" tire and 3.73's. Main thing i would do is if you have the 3.73's already is engine work, get some power and torque behind the 35" tires. A 35 is not a huge tire by any means. remember you are measuring from the center of the axle out when upping tire size not the whole height. So a 33 to a 35 is only 1" taller overall.

[beckmand78]

Originally Posted by mud.man.rj

Going from 3.73 to 4.10 is a bit of difference around town but not a substancial difference, especially for the $ spent. Like I mentioned earlier I run a 40" tire with 3.73's and a big block, so sure more power from the big block but the tires take up the difference and I run about 2,300 rpm @ 60mph highway with a 4spd manual, so yours being a 4spd auto and having the other top gear should be comparable with the 35" tire and 3.73's. Main thing i would do is if you have the 3.73's already is engine work, get some power and torque behind the 35" tires. A 35 is not a huge tire by any means. remember you are measuring from the center of the axle out when upping tire size not the whole height. So a 33 to a 35 is only 1" taller overall.

Isnt 4th gear in your truck 1:1? 700r4 is something like 1:.7.

I had 4.56s in my 02 with 35s. I dont remember exactly but i think it cruised at 2200-2300 at 70 on the highway.

[mud.man.rj]

It's all personal preferance, a lot of cash to change front and rear gear set, parts and labour, when some engine mods should easily take care of it, just trying to save a few $.

[beckmand78]

I agree with that. But it can be done on a budget. I paid just over $1200 for front and rear gears, all deals and bearings, and a detroit trutrac.

If you can find a REPUTABLE small 4x4 shop in your area, talk to the owner about the price. I got a huge discount by pulling my axles myself and delivering them to him.

[mud.man.rj]

It would be different if it had 3.08's but going from 3.73's to 4.10's is hardly any difference and trying to turn bigger rubber with a low hp engine is just way pushing the engine to hard and fuel mileage will be worse, so then step a low hp engine up to 4.56's and push it even harder makes no sense at all, why not invest the money into the engine and get something out of it, more torque is what pushs you ahead.

[LynnJr]

It will cost you the same amount of money to put 4.11's in it as it does 4.56 gears so get your gear choice figured out first before buying anything.
Going from 3.73 to 4.11 or 4.56 will lower the strain on the transmission and the engine both.
To test that out put your truck in high gear and try pulling away from a stop light or going uphill.
What rpm does the motor run at at your everyday cruising speed would determine your gear choice.You want the gears set up so the motor can accelerate without bogging it down but you also don't want it spinning 3500 rpm cruising down the interstate.
Automatics help you out a little bit due to the torque converter but the best bet would be to contact a local 4x4 club and find out what gear your "combination" likes best.
I am running 31's with a 5 speed stick and 3.42's and the truck is a dog after each gear change.Switching it over to a 400 sbc helped alot but going to 3.73's made all the difference in the world because I wasn't straining the engine on each shift with too wide of an rpm change.

[beckmand78]

Originally Posted by mud.man.rj

It would be different if it had 3.08's but going from 3.73's to 4.10's is hardly any difference and trying to turn bigger rubber with a low hp engine is just way pushing the engine to hard and fuel mileage will be worse, so then step a low hp engine up to 4.56's and push it even harder makes no sense at all, why not invest the money into the engine and get something out of it, more torque is what pushs you ahead.

it makes no sense that you say 4.56's will push an engine too hard. 4.56's make life much easier for the engine and trans.

Tire height isnt what matters most, its circumference.
circumference of a 31.8" tire is 99.22"
circumference of a 35" tire is 109.9"
That's a 10% difference, plus extra tire weight.

3.73 to 4.10 is a 10% increase, no bueno
3.73 to 4.56 is almost a 20% increase so it will compensate for tire weight as well as size.


I see that an engine with more torque would help, but that puts much more stress on the tiny stock axles.