I am doing it man! Don't try to stop me...
- Thread starter Skillet
- Start date
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You know, it's interesting that most all (if not all) the people saying 5.29's are overkill have never run them. It costs you ~250 RPM in OD, that's it. But if I spent a grand on 4.88's because I was scared of 5.29's, I'd sure be defending that choice.
I have run various final ratios in a very similar application. I went to 4.56 (stock is 3.51) on 31" tires on a modified XJ (Cherokee). AWD, 4.0L inline six, Toyota automatic transmission. I drove from Colorado to VA @ 3K RPM at 80 mph and then back towing a 5K trailer.
After this, I moved up to 32", 33", and 34" tires, reducing OD RPM by about 125 each time. Onroad, the large 34" trxus were actually better than the 33x10.5 BFG AT's, because they mated up better to OD off, but offroad it felt undergeared. The "paper math" for an XJ, BTW, was that 4.56 and 33" was "back to stock" and same basic argument for 4.88's and 35's on an 80, and I didn't like that ratio on 33's anywhere near as much as I liked it on 31's.
4.88's are now about standard in the Jeep world, even on the wimpy little 7" Dana 30. Those who go D44's up front tend to go 5.29. I've seen it all before...as hardcore usage percentage increases in a group forum the common wisdom on gearing will go lower, because real world experience and accurate information will become accepted and gearing is as important as lockers as usage difficulty increases (I stayed with stock gears on my 80 because I had pegged a difficulty level I didn't think I would exceed). There are a few early adopters of 5.29's, more will follow unless this forum has its typical Learning Cliff instead of a rational Learning Curve.
Anyway, going to 33x10.5 BFG over 31" BFG and reducing RPM by ~250 made no difference at all onroad except to more sluggish highway performance. This is the same basic thing as chosing 5.29 over 4.88 on an 80.
I knew this, which is why I chose 5.29, and it turned out exactly as I expected. At 75 mph, I run 2,900 RPM. At 70 mph, I run at 2,700 RPM, which is a real sweet spot. Unlike the guys running 2,400 RPM at this speed, which is just below the sweet spot, I can get up to 80-85 to pass in a heartbeat. The only part of my 80 that doesn't much care for this is my Interco tires.
This doesn't mean that most people won't be happy with 4.88 or that they aren't a better choice for most
. Simply that when you have an automatic transmission with OD, you can afford an entire level below what accepted "paper math" gearing ratio. What you are saying with this choice is simple: "Onroad, I don't want a 25% OD reduction because I don't have the power for that level of reduction and I'd rather it be a 5%-10% reduction compared to stock. Offroad, I want extra crawling performance."
It is nothing more or less than this beyond a non-empirical debate on R&P strength.
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Are there any computer adjustments needed when re-gearing?
It isn't needed. It is desirable. There is no reason to choose 33's over 35's just because you have stock gears, they both suck. You could do this for years. I wheeled in fairly hardcore conditions @ 10K feet with big 35's and stock gears.
My output of that was deciding that if I was going to regear I would push the onroad OD RPM limits, and there is also a perfectly logical output to that decision.
Had I listened to this board, I could have neither spent 2 years figuring out my real needs, nor gone 5.29's. I would have had to do 4.88's for those 35's even though stock gears are supposedly fine for 33's. My 80 was so capable on stock gears and 35's, especially with the control of the hand throttle, that I was pushing it and getting myself in trouble that was costing me money, and that was when I decided I'd better upgrade gearing to reflect my usage.
Rather than listening to the paper pushers here, I played out my requirements for myself and made a decision on gearing for myself. I encourage others to do the same, because a lot of the advice here is one size fits all, and unless you are a sock, I'd be careful with that.
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you should recalibrate the speedo. This will sync your shift points back to stock as well as properly display your speed.
There are several choices out there and they all basically do the same thing.
I originally thought this was a mistake but after running the calculations I see it's right. Makes me feel all the better about my choice of 4.88s as there really isn't much of a gearing difference between the two and then add the whole weaker debate of the 5.29s makes it seem like a safer choice.
Perfect. That is the only reason I am posting this stuff. Some will say "Only 250 RPM in OD, and I get the extra crawl ratio? No brainer." Others will agree that what you just said makes sense (and it does, of course).
I think the biggest thing people don't realize is how little movement there is between ratios in a four speed OD auto transmission in top speed RPM, and that you are shifting your "sweet spot" about 5-6 mph down by going a ratio lower. So where 4.88's would be ~75 mph @ 2,700 RPM, 5.29's are ~70 mph @ 2,700 RPM.
If you drive 65-70 anyway, you may find 5.29's are actually better on the highway than 4.88's. If you want to drive 75-80, you probably won't.
To Skillet's question of being on 305's (33's) now and wondering if he will like 315's on the 4.88's, the answer is simple. If you love your 33's and 4.88's, you will know what it would have been like to have 5.29's with your 35's. If you don't like 305's with 4.88's because you think they are too low, you'll be very happy with your choice.
I've got $20 that says we are going to see a post about how killer 305's and 4.88's are from our thread author in the near future, and I will be responding with a post that contains at least one
I never had any credibility to start with..................
So I was just reinforcing that point.
BTW, Romer has a supercharger. Guys with superchargers seem to always leave out that little point when responding to gearing threads. If I had a supercharger, the point of which is to drive faster, I would have gone 4.88's.
In fact, a local 80 owner with a SC asked me about 5.29's based on my threads and I talked him out of it. It's all part of a system. If you change a major variable like forced induction, your design elements have changed and other variables such as lift, tire type and size, etc. will change with it (unless you want to spend money fixing your mistakes).
All credibility lost using Romer as the basis for the voice of reason
If this doesn't create FUD (Fear, Uncertainty, and Doubt), I don't know what will
Says the guy for years who stated regears aren't needed for driving in the mountains with 35's and then became waffle boy and flipped to the other extreme.
I drive comfortably at 80 mph with 4.88's that give me more rpms at speed than stock. I would only go 5.29's if I was going to run 37's.
I also based my decision on the opinion of 3 people who I respect who told me 5.29's have smaller teeth and they are more prone to breaking under load. Two of them had seen broken 5.29's.
I believe Christo's opinion was (to paraphrase), if you try hard enough you can break anything.
That being said, when it comes to output shafts, higher spline counts are stronger due to the increase in surface area contact. I'm sure the law of diminishing returns applies here somewhere, but I would imagine that an individuals offroad driving technique has more to do with breakage than the gear itself. If you are heavy footed offroad, especially in wheel slippage situations, you are gonna break more stuff than if you slip, back off and try a little different line. (JMHO)
That being said, when it comes to output shafts, higher spline counts are stronger due to the increase in surface area contact. I'm sure the law of diminishing returns applies here somewhere, but I would imagine that an individuals offroad driving technique has more to do with breakage than the gear itself. If you are heavy footed offroad, especially in wheel slippage situations, you are gonna break more stuff than if you slip, back off and try a little different line. (JMHO)
Quite a few folks in the local club on higher gears. Might do better posting on the Rising sun forum as they are not all over here. I think just about everyone is on 4.88's: Uncle Ben, nakman, powderpig, Corsair23, Hulk and few that I don't remember. Uncle Ben and I are the only ones with a SC in that group.
We do all kinds of wheeling just short of rock crawling. Chinamans Gulch, Holy Cross, al over Moab, Spring Creek and even mild trails like Bill Moore lack and Jenny Creek.
The supercharger doesn't really come to play unless you are in boost mode (flooring getting on highway
) and when you are driving up mtn passes.
How would one do this when someone with 4.88 or 5.29 would have to go backwards or opposite of what the recalibration devices try to correct?
For example with stock gearing and 33" tires I would want to install a 31 tooth speedo gear ILO the standard 32 tooth in order to correct my speedometer. If I had 35" tires and 4.88 or 5.29 I have now overgeared putting me calibration problem the other direction. So they would need a 33 or 34 tooth speedo gear, correct?
Is there such corrections out there? Clear as mud?
They go +/- on correction. Yellow Box will give you +/- 28% to correct for over or under gearing.
BTW, Romer has a supercharger. Guys with superchargers seem to always leave out that little point when responding to gearing threads. If I had a supercharger, the point of which is to drive faster, I would have gone 4.88's.
CHRIST ON A BIKE I WISH I KNEW THAT!
fawkin Romer..................
I get your arguement for 4.88's, Romer... But aren't you supercharged?
sleeoffroad
Supporting Vendor
I have had the following:
SC with 4.88's and 315's - 1995 truck
No SC with 4.88's and 315's and 37" - 1995 truck
No SC with 5.29's and 37's - 1994 truck
The only way I would do 5.29's on 35's is if I did not care to drive over 70 mph. 5.29's with 315's is simply to much for running on the highway and 70/80mph.
SC with 4.88's and 315's - 1995 truck
No SC with 4.88's and 315's and 37" - 1995 truck
No SC with 5.29's and 37's - 1994 truck
The only way I would do 5.29's on 35's is if I did not care to drive over 70 mph. 5.29's with 315's is simply to much for running on the highway and 70/80mph.
yes, but it doesn't effect the choice of gears as far as I am concerned.
I think that if you have more power, gearing becomes less important on the street. Try driving a mini truck on stock gears and 35's, then a v-8 pickup with stock gears and 35's... one is a lot more livable than the other!
However, if you could put a 4.1 crawl box between our tranny and t-case, I would also be running 4.88's. But that is currently not available and 37's will be in my future. 5.29's FTW!
However, if you could put a 4.1 crawl box between our tranny and t-case, I would also be running 4.88's. But that is currently not available and 37's will be in my future. 5.29's FTW!
Skillet
Skillet
- Thread starter
- #59
So, my biggest issue is going slow up grades. The lower gearing on the trails will be a definite plus.
That being said, I carry a ton of weight in my rig and going the steep grade into Shelter Cove, CA last year I could not get over 25 - 30 mph.
Ridiculous.
I rarely drive over 70 mph for fuel efficiency reasons.
That being said, I carry a ton of weight in my rig and going the steep grade into Shelter Cove, CA last year I could not get over 25 - 30 mph.
Ridiculous.
I rarely drive over 70 mph for fuel efficiency reasons.
I'm just giving you crap since you posted that 4.88's are great and didn't post that you have a SC. And now you are saying the SC doesn't come into play except on mountain passes. We should pull up some threads on SC vs. turbo for the sake of consistency
And of course 4.88's with a SC and a bunch of really heavy accessories is less of a breakage risk than a lighter rig on 5.29's naturally aspirated
