4.56 gears

[Flyfisher]

I re-geared two weeks ago, so I'll chime in. It's a 2001 I-6 w/AW-4 turning 4.10 gears and 31" BFG ATs. I'm doing ~2450 rpms at 70 mph.

Wondering if JPs01XJ speed of 70mph was read by the speedometer, or by an GPS or ???. If he's re-geared and has non-stock tires, I'm sure the speedo isn't accurate. I'm not going to bother going through all the math (not that I'm not capable)...just think that the estimated 3,000 rpm's is high.

Just my $0.02

 

[REVROK]

Multiply your current revs at 65 times 1.285 and you will get you answer (revs will be 28.5% higher). The 4.0 likes to rev so you shouldn't have any real issues.

One of my best friends (and usual wheeling partner) ran around all last winter on 4.56 gears and 235/75/15 tires. He had no problems keeping up with me at 70 on the freeway and got damn near 20 mpg.

Yup! Why would 2500 rpm be a problem at 65 for mileage or anything? Slow down to 60 and I am betting on solid mileage. Get a Prius if you want better.

 

[robsjeepxj]

This is great thread so far. Full of just enough "actual" experience and facts to balance out the overwhelming amounts total bulls**t and outright lies. Carry on gentleman.

 

[REVROK]

I re-geared two weeks ago, so I'll chime in. It's a 2001 I-6 w/AW-4 turning 4.10 gears and 31" BFG ATs. I'm doing ~2450 rpms at 70 mph. I would think you'd be pushing 3000 rpm with 30" tires and 4.56 gears. I would say that's a bad combination.

Keep in mind that the straight six "likes" rpms only when it needs them, i.e., towing a very heavy load. And that's only because it's better than having the engine bogged down. Just cruising the highway at ~3000 rpm will just be extra wear and reduced mileage.

Check your figures at 70 your running about 2300 and on 30's with 4.56's he is running 2700 at 70... there is actually only an incremental difference between 4.10's and 4.56's, only 11%. In the OP I read the question to be if it is doable. Since the man is running 34's off road the gear ratio is anything but bad for his use.

 

[robsjeepxj]

I guess if I read this 20 years ago when I had my 70 EL Camino I would have been told I was out of my mind to think I could run a big block with a 2 speed powerglide, 5.13 rear and 30" slicks. What was I thinking? I'm glad the world didn't end or anything. God I loved that car.

 

[Lightfoot]

Im running 4.56's with 33's that actually measure just under 31.75", with an ax-15, and a stroker. In the last month I have done 4 trips from Fort Collins to Vail and back, a 300 mile trip. This includes probably 120miles at 75mph, 100 @ 65, 50 @ 55, and the rest in town. At 75, my rpm's are right at 3k, about 2500 at 65. I barely have to use 4th gear, even at 10,000 feet. The power is great, and I get right around 17.5mpg cruising in the fast lane on some of the steepest hills in the country. Miles traveled was determined using map quest to eliminate speedometer error.
If your only hitting 65, id say run the gears. when you get new tires, go with some 31's or bigger. So what if your motor pukes 500 miles sooner, by then you'll be looking for an excuse to drop in a small block anyway.

 

[wingnutooa]

i have 4.56's, 35's and an ax15. at 70 i'm doing 3500RPM, at 65 about 3300RPM~

i cant imagine it would be much lower with an aw4. especially with 30's..

i wouldn't doubt you'll see 3500+ on the highways, more often than you would like.

if you want to go with 4.56's for wheeling and have an extra set of wheels i would bank on getting some 33inch street meats instead of shooting for 31's

 

[REVROK]

i have 4.56's, 35's and an ax15. at 70 i'm doing 3500RPM, at 65 about 3300RPM~

:huh:

Funny how I am at 2050 at 65 on 33's with 4.10's with AW4 consistent with the calculator found here--- http://www.ringpinion.com/Calc_RPM.aspx

With the stick you are at 2400-2450 on 35's at 65... at 3300 you would be doing 85 plus, I am sorry but numbers don't lie. Are you using your speedo? Have it checked. Mine is based off my Tom Tom.

To the OP... just ignore the drama and use the calculator.

Hasta

 

[robsjeepxj]

His numbers are probably in 4th gear, which doesn't really count if you trying to compare apples to apples, it just puts more misinformation out there. Use the calculator and stop all the guessing, the calculator doesn't lie.

 

[ILLXJ]

I guess if I read this 20 years ago when I had my 70 EL Camino I would have been told I was out of my mind to think I could run a big block with a 2 speed powerglide, 5.13 rear and 30" slicks. What was I thinking? I'm glad the world didn't end or anything. God I loved that car.

Sounds like a fun car. JIM.

 

[robsjeepxj]

Sounds like a fun car. JIM.

Wish I still had it, it was scary fast.

 

[JPs01XJ]

I verified my speed by a GPS and another stock vehicle. My numbers are accurate. Good luck to the OP. Now I remember why I only read and don't post.

 

[american_zero]

Used a simple online calculator and it looks like with 31" tires, 3.55's in the axle, and leaving the AW4 in 3rd gear (1.0:1) will give you a very similar ratio to having 4.56's and going to OD. So if you're curious about highway RPM's just leave it in 3rd for a week or two and see how you like it. It's just a touch too buzzy for me, but the power is awesome. And you'll be turning a little bit faster with the 30's.

 

[87manche]

why not do the gears and get some 33" cheapy mall terrains or something for the road?

33's and 4.56's was awesome on te highway. I drove one from CO to OH with that combo.

 

[CherokeeBen]

Just remember that when using the calculator that you use the actual diameter of the tire. A 30" tire is probably closer to 29 than to 30. When I used the calculator to determine the gear ratio I wanted, I forgot about that and ended up turning higher rpms than what I calculated.

 

[87manche]

Just remember that when using the calculator that you use the actual diameter of the tire. A 30" tire is probably closer to 29 than to 30. When I used the calculator to determine the gear ratio I wanted, I forgot about that and ended up turning higher rpms than what I calculated.

that's a very good point.
some 33x10.5 road tires would go a long ways towards good mileage.

 

[nomoneysonny]

i have 4.56's, 35's and an ax15. at 70 i'm doing 3500RPM, at 65 about 3300RPM~

i cant imagine it would be much lower with an aw4. especially with 30's..

i wouldn't doubt you'll see 3500+ on the highways, more often than you would like.

This is a 4.0 in 5th gear?!

 

[Flyfisher]

i have 4.56's, 35's and an ax15. at 70 i'm doing 3500RPM, at 65 about 3300RPM~

i cant imagine it would be much lower with an aw4. especially with 30's..

i wouldn't doubt you'll see 3500+ on the highways, more often than you would like.

if you want to go with 4.56's for wheeling and have an extra set of wheels i would bank on getting some 33inch street meats instead of shooting for 31's

Really? Sheesh...I'm running 33's with 4:56's (4.0 with AW4 in OD). Get 2,750 rpms at 70 mph (GPS measured)....I kinda doubt you're runnign 3,500+ at 70mph with 35's, unless you're running in 3rd gear or something.

For my money, 4:56's are perfect for 33's...and OK for 35's. Pretty much back to, or just lower than stock at 33", and lower than stock on 35's.

Really? I mean really?

 

[cal]

i have 4.56's, 35's and an ax15. at 70 i'm doing 3500RPM, at 65 about 3300RPM~

i dont know how i missed this, but to be blunt you are so full of it your eyes are brown.

ax-15. 4.56 gears. 35's. 3000 rpm.

3rd gear: 48 mph
4th gear: 60 mph
5th gear: 87 mph

ax15, 4.56 gears, 35's, 3500 rpm

3rd gear: 56 mph
4th gear: 80 mph
5th gear: 101 mph

.. you need to learn to shift, or slow the hell down.

 

[old_man]

Just for everyone's info, Jeep offered 4.56's with stock tires. I ran them on 31's with a 4 banger for quite a while and got 27mpg. I still run 4.56's in my front and rear D44's on my stroker, but on 35's now.