Re-gear: Final questions before install

[chino1969]

Mine is a daily driver, and 4.56's work well for me. I won't go bigger than 33's, so the 35 scenario is irrelevant to me. Not to scare you from re-gearing, but some who have re-geared have experienced harmonic vibes as a result of faster drivetrain speeds post re-gear. Going too deep could exasperate the condition. Just my 2 cents.

Appreciate the feed back. Yeah, I've considered the possibility of harmonic vibes as a result of re-gearing. Will talk this over with shop. I don't want to get caught up in the endless cycle of putting more money out to correct a problem created by changing something. Hell, if I have to I'll stick with the 3.73 gears and just learn to live with them. I read too many threads here where people spend a lot of money to correct a problem that did not exist before they changed something that was tolerable. With the dynamic forces associated with spinning masses I certainly understand your point.

 

[chino1969]

4.88 is lower gearing than 4.56. Think of the larger number as a longer lever.

I'll add that when I move to 35" tires, my hope is to change my existing 4.88 to 5.13. And the funny thing is that the rpms will still be lower than my current setup with 33s.

Good way to equate the two; a longer lever. So the higher the number the easier it is for the gears to move the vehicle? I assume the time span between shifts is longer as well?

 

[jjvw]

Good way to equate the two; a longer lever. So the higher the number the easier it is for the gears to move the vehicle? I assume the time span between shifts is longer as well?

The early shifts don't last as long, though I tend to shift well above 3k. But because the overall rpms are higher, 4th/5th will be useful through a wider range of speed and terrain.

 

[chino1969]

I had the exact same setup as you and went with 4.56, a Detroit in the rear and a lockrite in front. I also said I would never go to 35s, and then I did after about 6 months. 4.88 would've been a little bit better with 35s, but it's still pretty good at 4.56. for me the 4.56 is just right for 33s.

Thanks for the reply. I can guarantee I will never go larger than 33" tires. Did you have any issues with the auto locker in the snow?

 

[chino1969]

The early shifts don't last as long, though I tend to shift well above 3k. But because the overall rpms are higher, 4th/5th will be useful through a wider range of speed and terrain.

Are you saying I'll be shifting more in the lower gears? I tend to shift at around 3k.

 

[Westtown Willy]

Appreciate the feed back. Yeah, I've considered the possibility of harmonic vibes as a result of re-gearing. Will talk this over with shop. I don't want to get caught up in the endless cycle of putting more money out to correct a problem created by changing something. Hell, if I have to I'll stick with the 3.73 gears and just learn to live with them. I read too many threads here where people spend a lot of money to correct a problem that did not exist before they changed something that was tolerable. With the dynamic forces associated with spinning masses I certainly understand your point.

Mine vibrated like a mohofuckiddy before and after my regear, it was an issue that was caused by an improper angle on my stock drive shaft and eliminated by ditching the slip yoke, putting in the correct shaft and tweaking the axle position with adjustable control arms. Yea, a lot of bs & money to eliminate vibes but you’ve got to do what you’ve got to do to get it done right. I understand the shaft is spinning faster with lower gears and that could aggravate the situation but you’ve got to pick your problem - between that and driving around with incorrect gearing for your tire size it’s a no brainer which way I’d go.

Don’t overthink this, you’ve got it narrowed down to two really good choices & I think you’ll be happy with either, you literally can’t make a mistake. The 4.56 will put you at stock rpms, would you consider that a good setup? I would. 4.88 will give you slightly higher rmps, it’ll be stronger when you’re on the highway in 5th going up hill among other things, would you consider that a good set up? I would. You can’t go wrong here. The key is to get away from gearing that’s too high because that’s what sucks.

 

[jjvw]

Are you saying I'll be shifting more in the lower gears? I tend to shift at around 3k.

Yes and no. You will move up through the gears more quickly. But once you are there, you will be able to hang on to a specific gear and speed range longer. You won't be constantly adjusting and downshifting due to a lack of power.

Another thing I really like about my low 1st gear is that creeping through slow traffic is so much easier.

My general argument is that lower gears for pavement makes the Jeep that much more livable.

 

[chino1969]

Mine vibrated like a mohofuckiddy before and after my regear, it was an issue that was caused by an improper angle on my stock drive shaft and eliminated by ditching the slip yoke, putting in the correct shaft and tweaking the axle position with adjustable control arms. Yea, a lot of bs & money to eliminate vibes but you’ve got to do what you’ve got to do to get it done right. I understand the shaft is spinning faster with lower gears and that could aggravate the situation but you’ve got to pick your problem - between that and driving around with incorrect gearing for your tire size it’s a no brainer which way I’d go.

Don’t overthink this, you’ve got it narrowed down to two really good choices & I think you’ll be happy with either, you literally can’t make a mistake. The 4.56 will put you at stock rpms, would you consider that a good setup? I would. 4.88 will give you slightly higher rmps, it’ll be stronger when you’re on the highway in 5th going up hill among other things, would you consider that a good set up? I would. You can’t go wrong here. The key is to get away from gearing that’s too high because that’s what sucks.

Thanks Willy. I've been talking with Gabe at the JP Shop and will be driving there tomorrow to meet face to face and discuss these possible scenarios. I'm certain those guys are qualified and experienced enough to be able to make it right. They want me to leave it with them for a week. I'm sold on the LSD Tru Trac for the rear but am still undecided about the front. I want to talk that over with Gabe or Keith. Everything else sound solid?

 

[chino1969]

Yes and no. You will move up through the gears more quickly. But once you are there, you will be able to hang on to a specific gear and speed range longer. You won't be constantly adjusting and downshifting due to a lack of power.

Another thing I really like about my low 1st gear is that creeping through slow traffic is so much easier.

My general argument is that lower gears for pavement makes the Jeep that much more livable.

Okay. That is what I am trying to minimize; the constant downshifting due to a lack of power. I also want to be able to hang on to a specific gear and speed range longer. Sounds like my reasoning is logical on this. Thanks.

 

[jjvw]

Thanks Willy. I've been talking with Gabe at the JP Shop and will be driving there tomorrow to meet face to face and discuss these possible scenarios. I'm certain those guys are qualified and experienced enough to be able to make it right. They want me to leave it with them for a week. I'm sold on the LSD Tru Trac for the rear but am still undecided about the front. I want to talk that over with Gabe or Keith. Everything else sound solid?

Can't speak to any specific shop, but having watched and read about these scenarios, many shops don't understand the peculiarities of our little engines and truck transmissions and larger tires. That is one reason so many still end up under geared. And there are a lot of outdated fears surrounding small pinions.

 

[chino1969]

Can't speak to any specific shop, but having watched and read about these scenarios many shops don't understand the peculiarities of our little engines and truck transmissions and larger tires. That is one reason so many still end up under geared. And there are a lot of outdated fears surrounding small pinions.

A couple of people on this site vouched for the shop as well as a couple of local Jeepers. I did stop to get a feel for these guys and they sound like they are qualified and experienced enough to be familiar with the peculiarities. There were quite a few serious off road capable TJ's in their parking lot which tells me they are pretty much Jeep specific. What do you mean by: And there are a lot of outdated fears surrounding small pinions?

 

[jjvw]

A couple of people on this site vouched for the shop as well as a couple of local Jeepers. I did stop to get a feel for these guys and they sound like they are qualified and experienced enough to be familiar with the peculiarities. There were quite a few serious off road capable TJ's in their parking lot.

If they can make a recommendation based on your specific transmission and tell you what the rpms should be at 75mph, then that is a good sign. However is they will gear the 3 speed and 4 speed automatics the same, then they can't be trusted to make a good recommendation.

Know this. With 4.88 and 33s and your 5 speed the rpms will be very close to 3k rpm at 75mph. Your shop should be able to tell you this.

 

[chino1969]

If they can make a recommendation based on your specific transmission and tell you what the rpms should be at 75mph, then that is a good sign. However is they will gear the 3 speed and 4 speed automatics the same, then they can't be trusted to make a good recommendation.

Know this. With 4.88 and 33s and your 5 speed the rpms will be very close to 3k rpm and 75mph. Your shop should be able to tell you this.

Good tip, thanks. Will put that in my mental tool pouch. I have had this Jeep up to 70mph and don't need to be going any faster.

 

[xxdabroxx]

I just got back from a 917 mile trip in my TJ to lake Tahoe and a brief stint on the Rubicon trail. I've got your same 5spd, 33" tires, and 4.56 gears. There was a lot of elevation change on this trip up to about 8700'. I spent a lot of time over 6400' and I would definitely go 4.88 if I had it to do over again. I really wish that my 5th gear was about halfway between my current 4th and 5th and I think 4.88 would get me closer to that.

Particularly at elevation you start losing a fair bit of horsepower and with the hills I'd really like the lower gears. There were some steep grades that I climbed at 55mph in 3rd gear. There were also times that I was in 4th and forgot after climbing a grade so it isn't like I'm too low geared now. I did up to 80mph on the flat freeway on the way back home and had no trouble. I don't think a couple hundred more RPM would be a deal breaker there either. If you are predominately at sea level on flat terrain I don't see why 4.56's wouldn't be great, but if you climb a lot of hills the 4.88's would rock. I also find on our local mountains that I'm between 2nd and third on the switchbacks and if I had lower gears I could stick to third more and shift half as much.

I also have a truetrac in the rear and if you aren't planning on lifting a tire in the rocks and spinning I'd totally recommend them front and rear. It has been absolutely great in everything I've had it in, snow, rocks, mud, ice, loose dirt, paving, etc.

 

[chino1969]

I just got back from a 917 mile trip in my TJ to lake Tahoe and a brief stint on the Rubicon trail. I've got your same 5spd, 33" tires, and 4.56 gears. There was a lot of elevation change on this trip up to about 8700'. I spent a lot of time over 6400' and I would definitely go 4.88 if I had it to do over again. I really wish that my 5th gear was about halfway between my current 4th and 5th and I think 4.88 would get me closer to that.

Particularly at elevation you start losing a fair bit of horsepower and with the hills I'd really like the lower gears. There were some steep grades that I climbed at 55mph in 3rd gear. There were also times that I was in 4th and forgot after climbing a grade so it isn't like I'm too low geared now. I did up to 80mph on the flat freeway on the way back home and had no trouble. I don't think a couple hundred more RPM would be a deal breaker there either. If you are predominately at sea level on flat terrain I don't see why 4.56's wouldn't be great, but if you climb a lot of hills the 4.88's would rock. I also find on our local mountains that I'm between 2nd and third on the switchbacks and if I had lower gears I could stick to third more and shift half as much.

I also have a truetrac in the rear and if you aren't planning on lifting a tire in the rocks and spinning I'd totally recommend them front and rear. It has been absolutely great in everything I've had it in, snow, rocks, mud, ice, loose dirt, paving, etc.

Thank you. Great feedback. I am definitely having a True Trac in the rear, may go with one in the front. I'll discuss the gear ratios with the shop tomorrow.

 

[Rob5589]

Okay. That is what I am trying to minimize; the constant downshifting due to a lack of power. I also want to be able to hang on to a specific gear and speed range longer. Sounds like my reasoning is logical on this. Thanks.

@jjvw explained it all but yes, less downshifting when climbing, a bit quicker upshifting from a start. Off road in 4lo, it will crawl nicely with less gas pedal and descend more controllably with less or no braking.

 

[jazngab]

@jjvw explained it all but yes, less downshifting when climbing, a bit quicker upshifting from a start. Off road in 4lo, it will crawl nicely with less gas pedal and descend more controllably with less or no braking.

All of this. When in doubt, choose the lower gear.

 

[AndyG]

Lower gearing off road, important on a manual trans. A bit better take off. Couple hundred rpm more at cruising speed so less downshifting. Better gearing if you ever go larger than the 33. 4.56 will work well, too, 4.88 just a bit better.

I can back this post -

I run 33” tires with 4:56 in an nv 3550. I like it so much , I know 4:88 would be a ball.


When I look at gear ratios , 4:56 and 4:88 are really bracketed closet together.

Someone once said on here , If given a choice , go to the highest. That has always hit me as a good one. I’d rather be a tad high than low .

So many good things come from regearing ....it’s not a mod , it’s an adjustment to bring rpm, horsepower and throttle position into an optimal relationship, as was originally designed .

 

[jazngab]

I can back this post -

I run 33” tires with 4:56 in an nv 3550. I like it so much , I know 4:88 would be a ball.


When I look at gear ratios , 4:56 and 4:88 are really bracketed closet together.

Someone once said on here , If given a choice , go to the highest. That has always hit me as a good one.

I like 4.56 on 31s so much so I don’t think I want to go to 33s when it’s time for new tires in a few years. Might stay 31 or 32 just to remain geared lower than my tire size.

 

[AndyG]

I like 4.56 on 31s so much so I don’t think I want to go to 33s when it’s time for new tires in a few years. Might stay 31 or 32 just to remain geared lower than my tire size.

I’d say that’s like 4:88 with 33’s.

But remember , I once dated a girl and sent her a card that said:” Even though we have only dated 4 months and 2 weeks and 3 days , it really feels like 6 months , 1 week and 4 days “