Nitro gears: 4.88 or 5.29? (1 Viewer)

[80t0ylc]

And by choice, if I had to tow, an 80 wouldn't be it.

Yeah, I hear you on that. Except for my squaredrop off road trailer, most of my towing is done with my 7.3L Powerstroke F350 now-a-days. And my 1st choice was the 4.88's when I started the upgrade to my 3rds. But after explaining the future use of my 80 to ZUK, who did the upgrades, he convinced me that 5.29's would be a better choice for my needs. He told me that he was amazed at the feed back he got from other 80 owners that he'd done their 3rds. A significant number of those that did the 4.88 wished they went with the 5.29. 4.88 is the ratio that puts 35" tires closer to OEM gearing, but so what?!? Many complain that the 1FZ and it's stock ratio sucks on hills. Some have gone the turbo route and say it's a different animal. I may do that if I ever rebuild mine. I'm above 295K now so it may not be far off.

 

[Marco Lau]

i have been running 37s on 488 with zero problem and complaints and its a 3FE...now i am on 529 and 37s, its a match made from heaven for it...

 

[Squeegee]

What power? Make up your mind. jk

If you don't wanna get buzzed by semis, you need to be pushing at least 75mph to which you're going to be in excess of 3K RPM when veering outside of stock ratios. That's a shtty driving experience in my book. I had 35s on 4.88s. Never felt right and I'd sell my dialed in 80 than go back to it.

Mine keeps up great with modern day traffic.

Sorry power band. I live in montana where the speed limit is somewhere between 75 and 80 so I go 80-85 most places. 1fzs are slow so why wouldn’t I want drive between 3k and 4K where it makes the most horse power.

As far as driving experiences goes, that’s personal preference I guess. I like keeping my 80 in the higher rpms. I don’t worry about it being comparable to stock ratios because it’s not a stock car

 

[bnh032]

I just did 4.88’s in my HDJ81 on 37’s. I’m at 2,800 rpm at 70+mph.

Hard to gauge how much it helped since I did a nomad valve body at the same time…. But those two mods made a night and day difference.

 

[Marco Lau]

I just did 4.88’s in my HDJ81 on 37’s. I’m at 2,800 rpm at 70+mph.

Hard to gauge how much it helped since I did a nomad valve body at the same time…. But those two mods made a night and day difference.

I am running 488 on 37s w/ underdrive Transfer high range gear set that puts me closer to 529 final. I am just a hair shy of 3k @ 70mph. My Nomad HD valve body is also making a huge diff. on highway pulling grade w/ 3rd gear lockup.

 

[bwakeling]

529s and 40's. Until I got the turbo I would have love more gearing.

 

[eurorom]

So putting a long though! I am doing Transfer Case gears. SUMO GEARS ready to be installed! Thoughts of going 37's in my next set of tires are looming in the not too distant horizon!

 

[SmokingRocks]

What power? Make up your mind. jk

If you don't wanna get buzzed by semis, you need to be pushing at least 75mph to which you're going to be in excess of 3K RPM when veering outside of stock ratios. That's a shtty driving experience in my book. I had 35s on 4.88s. Never felt right and I'd sell my dialed in 80 than go back to it.

Mine keeps up great with modern day traffic.

the 1fz makes peak torque at 3200rpm so holding 3000rpm on a highway cruise in top gear is perfect, especially when talking about a heavy rig at a mile above sea level. If the NVH gets to you then get a better resonator/muffler set up.

My 89' 320i with an S52 and ZF 5HP 18 5-speed transmission is buzzing along at about 4,200rpm at 80mph. That gets under my skin, the rear-end ratio is way to low.

 

[eurorom]

the 1fz makes peak torque at 3200rpm so holding 3000rpm on a highway cruise in top gear is perfect, especially when talking about a heavy rig at a mile above sea level. If the NVH gets to you then get a better resonator/muffler set up.

My 89' 320i with an S52 and ZF 5HP 18 5-speed transmission is buzzing along at about 4,200rpm at 80mph. That gets under my skin, the rear-end ratio is way to low.

Easy ..but how about your average gas mileage at 3000 rpm.?

 

[bwakeling]

Easy ..but how about your average gas mileage at 3000 rpm.?

is mileage even a consideration when driving a 80? lol

 

[Squeegee]

Easy ..but how about your average gas mileage at 3000 rpm.?

I got 13.6 mpg, going 80 ,keeping it between 3k and 4K going from Utah to Montana. My 80 is 6300lbs in 35s with 4.88s. Riding it right where the it makes torque keeps your foot out of the gas and keeps the duty cycle lower on the injector

 

[eurorom]

Great gas mileage!!

 

[SmokingRocks]

Easy ..but how about your average gas mileage at 3000 rpm.?

I don't care about MPG when driving the 80, my rig is 7k lbs (when loaded for week-long adventures off grid) it's lifted to the sky and has tires that weigh 100lbs each.

What I do care about is driver fatigue on the interstate for 8+ hours when I am driving to the start of my trips, I've found that the continuous shifting back and forth from 4th to 3rd greatly increases that fatigue. So if I lose .5mpg to maintain a higher level of alertness which only increases my safety then it's well worth it.

Also the argument of higher RPM using more fuel in the 80 is a bit mute and here's why. Let's say you are trying to maintain 80mph on the flat in a rig like mine (about as aerodynamic as a fully deployed parachute), if you have a final drive that lands your engine at say 2,250rpm @80mph you are going to need to really get into the throttle to maintain 80mph. If you have a final drive that is 1k higher at 3,250rpm to maintain 80mph you are barely going to be in the throttle. Which uses more gas? Idk but it's probably very close.

Lugging an engine outside of the meat of its powerband isn't an efficient way to drive, now I know the torque curve of the 1fz comes on early and is relatively flat so meh. I see the major benefit of having the final drive near the peak power rpm is that when going up any level of incline the rig can sit in 4th gear longer before or if at all needing to downshift for more power.

on 35's and stock 4.10's my rig would only hold 4th gear on the interstate if I was traveling no more than 75mph on the flat, any and I mean ANY incline brought on a shift.

 

[eurorom]

They are doing my transfer case gears as we speak. I am on 35"s. Looking forward to see how much I like my new power and!
If not then I can do differential gears as I go to 37" tires

 

[SmokingRocks]

So I ran some simple math to see if lugging a lower final drive rpm is more efficient than sitting at a higher final drive rpm. While the math is sound this is hypothetical and represents what you might see in a controlled laboratory environment.

So here's the math:
Cubic inch displacement/2 x RPM x (vacuum gauge reading divided by barometer reading).

the 1fz has 237 cubes so the formula looks like this; 273ci/2 x 2000 RPM x (24" manifold pressure divided by 29" barometric pressure)

The term “manifold pressure” is borrowed for aviation as a measure of the outside air pressure compared to the air pressure inside the engine’s intake manifold. It represents the drop in air pressure across the throttle & associated plumbing.


Scenario 1: 82% throttle at a lower 2,250rpm (lugging low gear)

273ci/2=137ci per rev (only half the cylinders are on intake stroke every revolution)

137 x 2250 RPM = 308,250 cubic inches per minute of airflow

308,250 x (24" manifold pressure divided by 29" barometric pressure) | represents 82% throttle

308,250 x .82 = 252,765 cubic inches per minute

Now we figure in the fuel/air ratio…

A/F= 13:1, so divide 252,765 by 13 and you get 19,443

The number 19,443 is not an absolute measurement like gallons or liters, but rather a number for comparison representing the consumption of fuel units.



Scenario 2: 41% throttle at 3,250rpm

273/2 x 3250 RPM x (12" manifold pressure divided by 28" barometric pressure)

273/2 = 137 (only half the cylinders are on intake stroke every revolution)

137 x 4000 = 548,000 cubic inches per minute of airflow

548,000 x (12" manifold pressure divided by 29" barometric pressure)

548,000 x .41 = 224,680 - more airflow here since there is more RPMs

Figure in the fuel/air ratio…

A/F= 13:1, so divide 224,680 by 13 = 17,283



The result? well 19,443 units of fuel to lug the engine at 2250 RPM @ 82% throttle, compared to 17,283 units of fuel to hold 3250 RPM @ 41% throttle.

So it’s almost a dead heat with lugging the engine using slightly more gas, but I'd surmise that the delta is statistically insignificant to really call it one way or another. The point is that a lower final drive is not always synonymous with better mpg.

 

[eurorom]

That is a very good evaluation or analysis! There are more factors involved. But it's never a decisive number!

 

[Squeegee]

I don't care about MPG when driving the 80, my rig is 7k lbs (when loaded for week-long adventures off grid) it's lifted to the sky and has tires that weigh 100lbs each.

What I do care about is driver fatigue on the interstate for 8+ hours when I am driving to the start of my trips, I've found that the continuous shifting back and forth from 4th to 3rd greatly increases that fatigue. So if I lose .5mpg to maintain a higher level of alertness which only increases my safety then it's well worth it.

Also the argument of higher RPM using more fuel in the 80 is a bit mute and here's why. Let's say you are trying to maintain 80mph on the flat in a rig like mine (about as aerodynamic as a fully deployed parachute), if you have a final drive that lands your engine at say 2,250rpm @80mph you are going to need to really get into the throttle to maintain 80mph. If you have a final drive that is 1k higher at 3,250rpm to maintain 80mph you are barely going to be in the throttle. Which uses more gas? Idk but it's probably very close.

Lugging an engine outside of the meat of its powerband isn't an efficient way to drive, now I know the torque curve of the 1fz comes on early and is relatively flat so meh. I see the major benefit of having the final drive near the peak power rpm is that when going up any level of incline the rig can sit in 4th gear longer before or if at all needing to downshift for more power.

on 35's and stock 4.10's my rig would only hold 4th gear on the interstate if I was traveling no more than 75mph on the flat, any and I mean ANY incline brought on a shift.

I had this explained to me like a year ago and it changed how I drive the car completely and resulted in way better mpg. I wish I learned it a long time ago

 

[80t0ylc]

So I ran some simple math to see if lugging a lower final drive rpm is more efficient than sitting at a higher final drive rpm. While the math is sound this is hypothetical and represents what you might see in a controlled laboratory environment.

So here's the math:
Cubic inch displacement/2 x RPM x (vacuum gauge reading divided by barometer reading).

the 1fz has 237 cubes so the formula looks like this; 273ci/2 x 2000 RPM x (24" manifold pressure divided by 29" barometric pressure)

The term “manifold pressure” is borrowed for aviation as a measure of the outside air pressure compared to the air pressure inside the engine’s intake manifold. It represents the drop in air pressure across the throttle & associated plumbing.


Scenario 1: 82% throttle at a lower 2,250rpm (lugging low gear)

273ci/2=137ci per rev (only half the cylinders are on intake stroke every revolution)

137 x 2250 RPM = 308,250 cubic inches per minute of airflow

308,250 x (24" manifold pressure divided by 29" barometric pressure) | represents 82% throttle

308,250 x .82 = 252,765 cubic inches per minute

Now we figure in the fuel/air ratio…

A/F= 13:1, so divide 252,765 by 13 and you get 19,443

The number 19,443 is not an absolute measurement like gallons or liters, but rather a number for comparison representing the consumption of fuel units.



Scenario 2: 41% throttle at 3,250rpm

273/2 x 3250 RPM x (12" manifold pressure divided by 28" barometric pressure)

273/2 = 137 (only half the cylinders are on intake stroke every revolution)

137 x 4000 = 548,000 cubic inches per minute of airflow

548,000 x (12" manifold pressure divided by 29" barometric pressure)

548,000 x .41 = 224,680 - more airflow here since there is more RPMs

Figure in the fuel/air ratio…

A/F= 13:1, so divide 224,680 by 13 = 17,283



The result? well 19,443 units of fuel to lug the engine at 2250 RPM @ 82% throttle, compared to 17,283 units of fuel to hold 3250 RPM @ 41% throttle.

So it’s almost a dead heat with lugging the engine using slightly more gas, but I'd surmise that the delta is statistically insignificant to really call it one way or another. The point is that a lower final drive is not always synonymous with better mpg.

Nice to see a scientific approach to your comments about lugging to maintain speed and mpg. It really does make sense. My experience and concerns with the 1FZ have been based on engine heat since modifying my OEM temp gauge and I can see what is actually happening. Plus adding weight through mods and increased tire size. Lower rpm's (below 2500 rpm) are fine on the flat and downhill. Engine temp climbs with any slope or resistance, such as headwind encountered. I've found that off road speeds, where the fan clutch is more involved because of lower speed and less wind driven air through the radiator, that engine temps can be brought down by using lower gears to increase rpm and force the fan to suck more air through the radiator. Even using lo - range when it isn't otherwise necessary. At highway speeds gearing down will help, but the difference is less noticeable. It seems to me that the stock 1FZ, with all the weight I've added, plus larger tires does better and is "happier" highway cruising between 2800 - 3500 rpm's than it would be with taller gear ratios. It's a lot to ask of the 1FZ to push a 7000 lb vehicle around on or off road. And add towing to that .... that's why I went and will stay with 5.29 with my rig, setup as it is.

 

[LC492]

has anyone tried running 4.88 gears with 40s on a 80s series?

 

[LC492]

has anyone tried running 4.88 gears with 40s on a 80s series?