Gearing/ RPM's?

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akarilo

akarilo

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Searched quite a few threads but the info is a bit jumbled; or perhaps it's my brain.

`97 LX, BFG a/t 315/75/16

Highway speed/rpm?

4:56 & 4:88

Input requested,

Thanx, KR
 
1996 FZJ80 on ProComp 315/75/16 geared with 4.88

My lead foot keeps me around 70mph... translates to about 2600rpm...
When not paying attention I climb to 75mph.... which pushes to nearly 3,000rpm

Those numbers come from my Scan Gauge II.... already adjusted for tire size and gear ratio.

Personally I think I am running a little high in the rpm's for a daily driver on 315's. If I wheeled it more then hwy driving I'd leave it with 4.88's. If I were to ever need to rebuild the 3rds again I would change to 4.56 gearing so that my highway speeds wouldn't result in such high rpm's on a constant basis. My wallet would appreciate it too.... I can almost watch the fuel level meter move as I fly down the freeway at 75 or higher....
 
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ChefFJ said:
1996 FZJ80 on ProComp 315/75/16 geared with 4.88

My lead foot keeps me around 70mph... translates to about 2600rpm...
When not paying attention I climb to 75mph.... which pushes to nearly 3,000rpm

Personally I think I am running a little high in the rpm's for a daily driver on 315's. If I wheeled it more then hwy driving I'd leave it with 4.88's. If I were to ever need to rebuild the 3rds again I would change to 4.56 gearing so that my highway speeds wouldn't result in such high rpm's on a constant basis. My wallet would appreciate it too.... I can almost watch the fuel level meter move as I fly down the freeway at 75 or higher....
Click to expand...

Exactly the kind of info I was looking for. I had my eyes set on 4.88's but after a little research I've been thinking 4.56's, as the rig sees quite alot of highway.

Others please chime in.
 
I like my stock gears.

I stick right at the speed limit, which is about 10% higher (haven't done a speedo correction mod yet), or about 71-72 MPH. Sit just above 2200 RPM.

At 55 MPH on the speedo (61 MPH real life) I'm almost exactly at 2k RPM.
 
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Ebag333 said:
I like my stock gears.

I stick right at the speed limit, which is about 10% higher (haven't done a speedo correction mod yet), or about 71-72 MPH. Sit just about 3200 RPM.

At 55 MPH on the speedo (61 MPH real life) I'm almost exactly at 3k RPM.
Click to expand...

Huh? That seems way high to me. I'm on 33's and stock gears, and cruising at 55 mph (corrected) I'm at 1800RPM. 70 mph is about 2300.

You know your transmission has a 4th gear eh? :D
 
96r50 said:
Huh? That seems way high to me. I'm on 33's and stock gears, and cruising at 55 mph (corrected) I'm at 1800RPM. 70 mph is about 2300.

You know your transmission has a 4th gear eh? :D
Click to expand...

Whoops, fixed. :doh:
 
I still have my stock gears and 295's. Can't wait to re-gear, but going to until I goto 315's. Then it will be 4.88 for me. At your lower altitude I'd probably stick with 4.56 but with my constant trips up the mountain a little extra grunt will be appreciated. I'm also lucky in the fact I see very little HWY time day to day. My commute does not see speeds in excess of 50MPH.
 
ChefFJ said:
1996 FZJ80 on ProComp 315/75/16 geared with 4.88

My lead foot keeps me around 70mph... translates to about 2600rpm...
When not paying attention I climb to 75mph.... which pushes to nearly 3,000rpm

Those numbers come from my Scan Gauge II.... already adjusted for tire size and gear ratio.

Personally I think I am running a little high in the rpm's for a daily driver on 315's. If I wheeled it more then hwy driving I'd leave it with 4.88's. If I were to ever need to rebuild the 3rds again I would change to 4.56 gearing so that my highway speeds wouldn't result in such high rpm's on a constant basis. My wallet would appreciate it too.... I can almost watch the fuel level meter move as I fly down the freeway at 75 or higher....
Click to expand...

This sounds high for 4.88's to be @ 3,000 RPM @ 75 mph.

I ran 5.29's with 35's and was right around 3,000 RPM @ 75 mph, with GPS set yellow box speedo correction.

I would expect 4.88's to cruise 70 mph at about 2,400 or so.

Don't get 4.56's for 35's, that's a waste of regearing, unless you plan to drive consistently 80-90 mph.

If you cruise 70-75, IMO 4.88's are a no brainer unless you wanted lower gearing (5.29) not higher. 4.88's leave you about 6% lower than stock on 35's - an ideal combo for most people.
 
1FZFE_RPM.jpg
 
So, when I had 285/75R16 on 4.10 WITH a spedo correction gear I got from Slee, my speedo read about right -off a bit, but not bad.

I'm on 315/75R16 on 4.10 now, still have the speedo gear in - it is now way off of course.

I'm moving to 315/75R16 on 4.88 inside of a month. Which would be closer for the speedo, leaving in the Slee speedo gear or going back to a factory speedo gear?

If I'm reading that chart right - I should leave the Slee speedo gear -in- and not go back to a factory speedo gear?
 
I am going to regear soon. Listen to Nay and Landtank. I have reserched this for quite some time. The 4.56 are a waist of time and money. Go 4.88 they will help compinsate for the added unslung weight of the tires as well.
 
mister said:
I am going to regear soon. Listen to Nay and Landtank. I have reserched this for quite some time. The 4.56 are a waist of time and money. Go 4.88 they will help compinsate for the added unslung weight of the tires as well.
Click to expand...

Yes, it sounds like I will loose all credibility if I go 4.56:crybaby:

After looking at the chart, if I'm happy with 70mph, the engine wont be revving too bad.

OK, it's 4.88's. Anybody got $1200 bux I can borrow?
 
Newbie translation?

medtro said:
1FZFE_RPM.jpg
Click to expand...

So what is the stock set at for gearing? I'm assuming that it is the 5.29, since that's the only one that I can't find gear changes for...
I'm going to assume that the stock tire size is the 275 70 16- I would check on mine, but i can't physically access it right now...

So can someone explain what this chart means to someone stoopid :flipoff2: like me? How do RPM's reflect Gas mileage- I know lower RPM means lower gas milage... Your Help is Much appreciated-

*EDIT*

:o :whoops::doh:
I understand now that it's 275/70/16 and a 4.10- :bang::bang: Now that i feel stupid...
 
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Yes seriously- I was using the numbers i knew- I've done absolutely no tinkinering, and I can't get at any of my paperwork- That probably was common sense, and I felt stupid asking, but that's the truth....

So from this chart, i gather that the Lower the RPM, the better the gas mileage at high speeds? What does that do to lower speeds? For instance, what would happen to my city gas mileage if i changed my tires to 285/75/16's with the 5.29? Freeway? I just don't know how these work... Thanks for putting up with my stupid questions... but these are answers that i don't just know....
 
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