Gears -- 4.56 or 4.88? (1 Viewer)

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Hondo

Hondo

Joined
Mar 15, 2005
Threads
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Location
Phoenix, AZ
I've searched and have found no real collection of good information on this matter, other than the statement that 4.56s will bring me back to stock form...

I live in the mountains of Northern Arizona (approx. 7000' asl). I am currently running 315/75/16s with the stock gears, but would like to change out my gears to get better performance on the freeway while climbing steep mountain grades at these higher elevations, and at the same time improve my offroad performance. I know that running 4.88s will give me better torque for offroad driving, but I don't want to get a gear that is so low that it causes me to run my rpm's up excessively. In the past I had a CJ7 with a Chev. Turbo 400 3 speed auto (no overdrive) and 4.56 diff gears. In that application, I could not comfortably drive over 65 mph on the freeway without running the rpm's way up. For my FZJ80 ('94) I'm trying to get good power back, without having the same scenario.

Here's what I'm looking for (and to possibly make this a good FAQ for others):
An ability to compare side by side the information from those folks running 4.56 gears and from those running 4.88s. (And perhaps to compare the results from those that are also supercharged vs. stock)

Info such as:
- Year of your FJ80/FZJ80(to know which motor you're running)
- Which gear brand and ratio you have
- Primary elevation at which you drive
- Actual RPMs at different speeds
- Your impression of the truck’s ability to climb up steep grades at speed -- necessary to downshift (out of overdrive) to continue at speed?
- From those running 4.88s, do these gears feel like they may be too much for freeway driving?
- For those running 4.56s, do you wish you’d gone ahead and installed 4.88s?
- Any other information you feel might be helpful


Thanks,
Mike
 
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I have 4.56's and love them, gave me alot more pep, and no trouble with my 33's. For a second I considered 4.88's but thought it would be to much.
 
Mike,
You've basically answered your own question.

As you noted, with 35" tyres and 4.56:1 gears your truck will perform very closely to when it was stock (4.10:1 and 31" tyres)

Therefore, if the stock performance (RPM, climbing grades, mileage, etc.) was acceptable to you then go with 4.56 gears. If you yearned for a little more ooomph off the line, off-road climbing, etc, then your choice is 4.88 gears.

-B-
 
Not to be rude, but the reason I'm looking to get info from those with personal experience running the gears, is that higher elevations tend to sap the motor's power. With the stock size tires and gears it was alright, but did leave a little to be desired. I would just order the 4.88s based on this, but I want to make sure that running at freeway speeds (75-80mph) I won't be pushing the motor into the higher rpms. Also, I had hoped that some quality information might be collected for others, when the time comes to choose gears.
Thanks,
Michael
 
Hondo said:
Not to be rude, but the reason I'm looking to get info from those with personal experience running the gears, is that higher elevations tend to sap the motor's power. With the stock size tires and gears it was alright, but did leave a little to be desired. I would just order the 4.88s based on this, but I want to make sure that running at freeway speeds (75-80mph) I won't be pushing the motor into the higher rpms. Also, I had hoped that some quality information might be collected for others, when the time comes to choose gears.
Thanks,
Michael
Click to expand...


Michael,

with my 4.56s at highway speed I don't go beyond 2800 rps when going 75-80mph. Due to gas prices I try to stay under 68mph and usually stay withing 2200-2500 rpms. don't know if that helps you or not
 
Landtank runs 4.88's with 315's at close to sea level. Almost of his driving is hiway as he travels all over the northeast to do remote repairs as a part of his job.He is very fond of that combination.

At your altitude you would be well served by 4.88's with 35 inch tires. The other option is to fit forced induction to the engine to compensate for the altitude.

D-
 
This is a good question, and I'd like to add my own. Has anyone went with 4.56's and 35's and regretted not going with 4.88's? I really like the idea of getting back to stock, but I also would like the truck to move again.

Driving through New Mexico 3 weeks ago with my current setup, I was required to keep the pedal to the floor more than I liked just to maintain 55 at times.
 
To answer the original question, I have precision 4.88s w/ 35" TrXus Mud Terrains I used a install kit from Christo. Most of my driving is along the east coast. I don't pay attention to my RPMs but I often wish I went with 5.29s.
:beer:
 
Larger diameter tires have more mass and resistance to movement so overgearing just a bit is benificial. 4.88s and 35s is a very nice combo and the truck feels snappy off the line. 4.56 is not enough of a change from stock to be worthwhile in my opinion. At 75 mph, I run just over 2600 RPM.
 
Andrew and Curran both mirror Landtank's take.

I'll toss this bit in for thought:

IF you have in your plans a desire to switch back and forth between a hiway set of tires and an off-road set of tires AND you plan to run stock tires on the road, you DO NOT want 4.88 gears I would not go lower than 4.56 for stock tires.

D-
 
I run 4.88's in mine and only have 33's. When I bought the truck it was on "35" inch muds. When I measured them they were just under 33"s so I put my swampers on which measure just over 33. I can run down the interstate at 80 quite well. I think Im running around 2500-2800.
 
cruiserdan said:
Andrew and Curran both mirror Landtank's take.

I'll toss this bit in for thought:

IF you have in your plans a desire to switch back and forth between a hiway set of tires and an off-road set of tires AND you plan to run stock tires on the road, you DO NOT want 4.88 gears I would not go lower than 4.56 for stock tires.

D-
Click to expand...

I believe you are speaking of mud tires versus street tires in this instance, and not of stock size versus bigger than stock.

I do not understand why the choice between mud tires and street tires should affect gearing ?


Kalawang
 
Kalawang said:
I believe you are speaking of mud tires versus street tires in this instance, and not of stock size versus bigger than stock.

I do not understand why the choice between mud tires and street tires should affect gearing ?


Kalawang
Click to expand...

To me it reads like he is saying that if he plans to run stock tires for on road and larger offroads for said purpose, that he will not like that gear ratio as with the stockers it will "wind up" very high.

Sorta like saving money by not buying a set of on road, and off roads, rather keeping the old tires for roads and buying a new set for offroad.

Or something like that.......
 
Correct. I was refering to diameter not tread design.
 
315/35" tires and 4.88s are a perfect fit. I run BFG AT Kos during summer and X-Terrains in the winter. Great gas mileage and the truck feels like it is 1000 lbs lighter with that setup.

IMHO, 4.56s are a complete waste of time, a lot less bang for the buck. However you will need a truespeed calibrator or other frequency converter to get your speedo back in sync. So even if the gearing are the same price there is some additional costs that go with the lower gears.
 
Thank you Skyshark and Cruiserdan for the clarification. It makes better sense now.


Kalawang
 
- Year of your FJ80/FZJ80(to know which motor you're running)
>'96 FZJ80

- Which gear brand and ratio you have
>Precision 4:56

- Primary elevation at which you drive
> 1,000 ft or less

- Actual RPMs at different speeds
> I think around 2600 at 75 (not sure)

- Your impression of the truck’s ability to climb up steep grades at speed -- necessary to downshift (out of overdrive) to continue at speed?
>driving in Denver, my vehicle (fully loaded with gear at 7000 lbs) sucks ass. :crybaby:

- For those running 4.56s, do you wish you’d gone ahead and installed 4.88s?
>if I lived in 5,000' or higher, then 4.88s is the way to go.

- Any other information you feel might be helpful
>Most of my long hauls are into CO, UT, NM, AZ states from the Chicago area. Getting there with 4.56s is great. However, climbing steep grades at higher elevation usually puts me in 3rd gear (OD off). Usually, I'll be in Power mode at the high elevation driving just to get out of my own way :D However, this doesn't bother me too much because I live in the Midwest with an elev of <1000'. My vehicle weighs 6,000 lbs dry.

With this combo(4.56s and 315 75 16), I am using the stock speedo gear and the speedo/odo is dead nuts.

Ali
 
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alia176 said:
- Any other information you feel might be helpful
>Most of my long hauls are into CO, UT, NM, AZ states from the Chicago area. Getting there with 4.56s is great. However, climbing steep grades at higher elevation usually puts me in 3rd gear (OD off). Usually, I'll be in Power mode at the high elevation driving just to get out of my own way :D However, this doesn't bother me too much because I live in the Midwest with an elev of <1000'. My vehicle weighs 6,000 lbs dry.
Click to expand...

For me driving up any grade at any elevation forces me to drop down into 3rd gear with my current tires and stock gearing. At higher elevation I'm sometimes forced to drop down in 2nd (If the grade is steep enough).

Ali, what speeds are you maintaining when you drop down into 3rd? Your arguments are making me thing 4.56's again. I like the fact that the speedo is back to stock (after I swap in the stock gear) and that the RPM's aren't too high. I don't mind it if my truck is a little slow. After the 6 inch lift my truck became really slow. Drag isn't fun.

Unfortunatley the guys with 4.88's and no speedo correction can't really comment on the speed relative to RPM's without some other way to measure speed. I should probably do the math to figure out the RPM's at 80 mph with 4.88's and 4.88's.
 
Hondo, what gears did you end up going with? Any regrets? I'm debating between 4.56 and 4.88 myself, was happy to stumble across this thread this evening. I think I'm now about 60/40 in favor of 4.88 after reading this... was about 60/40 the other way before. :rolleyes:
 
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