Just Went to 33s / Do I Go to 4.30 or 4.56 ?

[Wheelin98TJ]

Lugging and subsequent engine failure is not economical (not that you're lugging the engine at 2k rpms and low load either but you seem convinced that's the case). They are geared that way for fuel economy because 2k rpms is more efficient than 2500 especially under light loads. If you let the automatic do its job you'll never lug the engine. The load goes up, downshift. Load goes down, upshift. That's how it's supposed to work. It was never intended to be geared so low it would hold 8th under moderate to heavy loads. That defeats the purpose of having 2 overdrives and 8 gears.

It wouldn't be geared so low that is will hold 8th under a moderate to heavy load.

As you said, load goes up, it downshifts. Load goes down, it upshifts.

If it's geared so it can run in 8th, it's running in 8th because it's not under a moderate-heavy load.

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[Zachanadandy]

It wouldn't be geared so low that is will hold 8th under a moderate to heavy load.

As you said, load goes up, it downshifts. Load goes down, it upshifts.

If it's geared so it can run in 8th, it's running in 8th because it's not under a moderate-heavy load.

The op geared all the way to 4 56s with 33s. That's 2700 rpm at 85mph, no it won't downshift under moderate loads. Heavy loads of course it will. My problem with gearing that low isn't the downshifts, is the lack of upshifts under light loads as there are no more gears after you hit aibout 40mph and it's already in 8th. Again I'm speaking from experience having run 5.38s with 38s which is almost the save as the OPs current gearing (5.30 with 38s would be identical). What is the point of 8 speeds and 2 overdrives when you've geared so low you've used them all by half the speed limit? What's the point of running 2700rpms under very light loads like the 20+ mile downhill section of freeway coming down into baker,CA outside of Vegas (a drive I treasure many times a year) when I could easily do the same a 2000-2200 with proper gearing that matches the factory ratios available? Even 4.56s and 35s felt like they were geared too low for freeway speeds behind the 3.6L to me. I'm not arguing that 2700rpm is redlining the thing or that it's hard on the engine, but to me the point of a second overdrive is to have low rpms at high speeds under light loads and comparing all the factory offerings jeep engineers clearly agree. Some quick math matching factor gearing to 37s...3.45s and 32s=4.00 gears. 3.73s and 32s=4.31. 3.73s and 33s=4.18. 4.10s and 33s=4.59. 4.56 and 35s=4.82. According to jeep engineers the appropriate gears for 37s would be somewhere between 4.10s and 4.88s and I agree whole heartedly. The problem is the guys who either rarely drive over 65mph or the guys who are used to running 3500rpm on the freeway behind a shit 3 soeed come on here and insist that running severable ratios below that is better. I fell for that rhetoric and spent $3k making my jeep no better off road and much worse on road once so I'll continue to comment on every gear thread where someone asks and break down my own personal experience and the math for them.

 

[AstroZombie]

Thanks. Ordering a Tazer Mini today.

Jscan is way less money!

 

[ShadowsPapa]

The op geared all the way to 4 56s with 33s. That's 2700 rpm at 85mph, no it won't downshift under moderate loads. Heavy loads of course it will. My problem with gearing that low isn't the downshifts, is the lack of upshifts under light loads as there are no more gears after you hit aibout 40mph and it's already in 8th. Again I'm speaking from experience having run 5.38s with 38s which is almost the save as the OPs current gearing (5.30 with 38s would be identical). What is the point of 8 speeds and 2 overdrives when you've geared so low you've used them all by half the speed limit? What's the point of running 2700rpms under very light loads like the 20+ mile downhill section of freeway coming down into baker,CA outside of Vegas (a drive I treasure many times a year) when I could easily do the same a 2000-2200 with proper gearing that matches the factory ratios available? Even 4.56s and 35s felt like they were geared too low for freeway speeds behind the 3.6L to me. I'm not arguing that 2700rpm is redlining the thing or that it's hard on the engine, but to me the point of a second overdrive is to have low rpms at high speeds under light loads and comparing all the factory offerings jeep engineers clearly agree. Some quick math matching factor gearing to 37s...3.45s and 32s=4.00 gears. 3.73s and 32s=4.31. 3.73s and 33s=4.18. 4.10s and 33s=4.59. 4.56 and 35s=4.82. According to jeep engineers the appropriate gears for 37s would be somewhere between 4.10s and 4.88s and I agree whole heartedly. The problem is the guys who either rarely drive over 65mph or the guys who are used to running 3500rpm on the freeway behind a shit 3 soeed come on here and insist that running severable ratios below that is better. I fell for that rhetoric and spent $3k making my jeep no better off road and much worse on road once so I'll continue to comment on every gear thread where someone asks and break down my own personal experience and the math for them.

I decided to watch mine a bit more closely lately, reading what you're saying about gearing and such and noticed that with the stock tire diameters, it's very very interesting to see that if there's a wind, or on our up-hills here, running speed limits puts mine running just in that 2900 RPM range - hey, high lift mode, higher oil pressure, etc. - those engineers nailed the gearing on this thing. It's right exactly where it needs to be running for the better breathing of the engine and due to that, it's right away doing better.
I thought it quite interesting to see that quite often, the transmission was shifting exactly where and when and how it should to nudge that engine just into the high lift intake mode. Hmmm, am I just putting something there that doesn't exist, or, was there some sort of thinking behind all of that when these were programmed?
Maybe it's just pure coincidence -
I mean, what the heck do engineers know about shift points, gearing, heat rejection vs. RPM vs. load and so on that people on the internet don't know more about? (just ask 'em)

 

[Wheelin98TJ]

The op geared all the way to 4 56s with 33s. That's 2700 rpm at 85mph, no it won't downshift under moderate loads. Heavy loads of course it will. My problem with gearing that low isn't the downshifts, is the lack of upshifts under light loads as there are no more gears after you hit aibout 40mph and it's already in 8th. Again I'm speaking from experience having run 5.38s with 38s which is almost the save as the OPs current gearing (5.30 with 38s would be identical). What is the point of 8 speeds and 2 overdrives when you've geared so low you've used them all by half the speed limit? What's the point of running 2700rpms under very light loads like the 20+ mile downhill section of freeway coming down into baker,CA outside of Vegas (a drive I treasure many times a year) when I could easily do the same a 2000-2200 with proper gearing that matches the factory ratios available? Even 4.56s and 35s felt like they were geared too low for freeway speeds behind the 3.6L to me. I'm not arguing that 2700rpm is redlining the thing or that it's hard on the engine, but to me the point of a second overdrive is to have low rpms at high speeds under light loads and comparing all the factory offerings jeep engineers clearly agree. Some quick math matching factor gearing to 37s...3.45s and 32s=4.00 gears. 3.73s and 32s=4.31. 3.73s and 33s=4.18. 4.10s and 33s=4.59. 4.56 and 35s=4.82. According to jeep engineers the appropriate gears for 37s would be somewhere between 4.10s and 4.88s and I agree whole heartedly. The problem is the guys who either rarely drive over 65mph or the guys who are used to running 3500rpm on the freeway behind a shit 3 soeed come on here and insist that running severable ratios below that is better. I fell for that rhetoric and spent $3k making my jeep no better off road and much worse on road once so I'll continue to comment on every gear thread where someone asks and break down my own personal experience and the math for them.

You must've missed the part where OP said he was going to 35s and geared accordingly.

 

[Heavy D]

You must've missed the part where OP said he was going to 35s and geared accordingly.

They've also missed the part about me being very happy with my new gears and the way my JT runs now....
But what do I know.. I'm not an engineer.
My ignorance is truly bliss.

 

[Zachanadandy]

You must've missed the part where OP said he was going to 35s and geared accordingly.

And that falls at the far end of gearing which is what I've been saying this whole time. 4.56s and 33s would suck, 35s still felt overgeared. Personally I would stick with 4.10s and 35s, 4.56s and 37s or 4.88s and 39s. Yes he stated somewhere along the way he'd go to 35s, but read the thread title again. For 33s I wouldn't waste the money swapping the 3.73s. If your gearing is already within 1 gear ratio of where you'd regear to, it is hard to justify the spend which is why I'm currently running 4.10s and 37s and 4.56s and 39s on our 2 rigs. I'm happier with this higher side of gearing than I was with gearing too low. Your results may vary.

 

[Jakef7]

I did not like my JT with 3.73s.
I love my JT with 4.56s.
We can just agree to not agree on embracing gear swaps.
[/QUOTE

We definitely have different opinions on this.

I'd rather be spinning 2,500 RPM on the highway because these low HP 3.6L V6 motors do not like lugging at 2,000 RPM. They can't do it when the OD reduction is 0.67 unless going downhill or with a tail wind. Now a 400 HP V8, sure, those will cruise at 2,000 RPM on the highway all day long and be happy.

The first gear ratio of a JT compared to anything else is not relevant to me. I'm not regearing for the benefit in first gear. I'm not in first gear that often. If I were to regear mine, it would be to be able to cruise in overdrive on the highway. Currently with 3.73 and 35s, mine wants to run around in 6th gear most often. I basically turned my 8 speed into a 6 speed when I slapped 35s on and didn't regear.

I’m with you on this. I’d much rather be cruising at an RPM that will hold overdrive other than the trans constantly down shifting to make up for not enough HP/TQ and that is exactly what the JT does. I still have the factory tires and 3.73’s and it constantly shifts back and forth through 6th, 7th and 8th on the highway with the slightest headwind or incline. And to say that it wasn’t designed to hold overdrive or a high gear, well that’s obvious folks. They tuned the transmission to behave the way it does because the engine is underpowered!!! If it had more power, it would hold overdrive a lot better than it does. However, installing a steeper set of gears will help mask this underpowered V6 motor, and that’s exactly what I plan to do in the very near future.

 

[Zachanadandy]

I’m with you on this. I’d much rather be cruising at an RPM that will hold overdrive other than the trans constantly down shifting to make up for not enough HP/TQ and that is exactly what the JT does. I still have the factory tires and 3.73’s and it constantly shifts back and forth through 6th, 7th and 8th on the highway with the slightest headwind or incline. And to say that it wasn’t designed to hold overdrive or a high gear, well that’s obvious folks. They tuned the transmission to behave the way it does because the engine is underpowered!!! If it had more power, it would hold overdrive a lot better than it does. However, installing a steeper set of gears will help mask this underpowered V6 motor, and that’s exactly what I plan to do in the very near future.

Gears are half the cost of a supercharger, why mask the lacking power when you could just fix it? The thing has a manual mode, must running it in 7th is the same as running 5.13s and 8th gear and far cheaper than a regear.

 

[Jakef7]

Gears are half the cost of a supercharger, why mask the lacking power when you could just fix it? The thing has a manual mode, must running it in 7th is the same as running 5.13s and 8th gear and far cheaper than a regear.

I have looked into doing a supercharger. However, from my research you’re looking at 10k including install, which is far more expensive than a re-gear. I can do gears for $2400.

yes, I’m aware that I can switch to manual mode and choose whatever gear that I want. However, I bought an automatic so I could let the computer do the work for me.

 

[Zachanadandy]

I have looked into doing a supercharger. However, from my research you’re looking at 10k including install, which is far more expensive than a re-gear. I can do gears for $2400.

yes, I’m aware that I can switch to manual mode and choose whatever gear that I want. However, I bought an automatic so I could let the computer do the work for me.

And then complain about the automatic shifting...automatically. A procharger kit can be had under $7k and if you can change an alternator you can install one. Gears locally were $3k installed. Gearing did nothing to add power that downshifting won't is my point, aside from 1st gear.

 

[ShadowsPapa]

And then complain about the automatic shifting...automatically. A procharger kit can be had under $7k and if you can change an alternator you can install one. Gears locally were $3k installed. Gearing did nothing to add power that downshifting won't is my point, aside from 1st gear.

The owners manual, which no internet forum user ever bothers to open or read, even says to use MANUAL MODE at times when there is frequent shifting.
That's exactly what I do when towing in our hills, or up in NW Iowa where the hills are so bad I can count a dozen up shifts and down shifts in a minute's time (they are hills, but really short hills spaced closer together, so just as you hit a low gear to get up that hill, you crest it and upshift again)
So while driving up to Spirit Lake, I locked that @#$% into a gear.
Wow, can't believe how simple it is, even I figured it out - bump the lever over, choose a gear that works well for up and down hills, let it ride.
Then later I read that silly book - hey, they are suggesting to do what I did! Cool.
And I do use manual mode while towing on sections of I80 east of here where even the OTR drivers are shifting up and down, up and down, blowing black smoke on this side of the hill, using engine braking on the other side.

 

[Wheelin98TJ]

The owners manual, which no internet forum user ever bothers to open or read, even says to use MANUAL MODE at times when there is frequent shifting.
That's exactly what I do when towing in our hills, or up in NW Iowa where the hills are so bad I can count a dozen up shifts and down shifts in a minute's time (they are hills, but really short hills spaced closer together, so just as you hit a low gear to get up that hill, you crest it and upshift again)
So while driving up to Spirit Lake, I locked that @#$% into a gear.
Wow, can't believe how simple it is, even I figured it out - bump the lever over, choose a gear that works well for up and down hills, let it ride.
Then later I read that silly book - hey, they are suggesting to do what I did! Cool.
And I do use manual mode while towing on sections of I80 east of here where even the OTR drivers are shifting up and down, up and down, blowing black smoke on this side of the hill, using engine braking on the other side.

Jakef7 said "it constantly shifts back and forth through 6th, 7th and 8th on the highway with the slightest headwind or incline".

Doesn't sound to me like he is towing or in big hills like you.

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