Any regrets going automatic?

[PatrickR]

You are mistaken, I never said torque multiplication happens at all speeds. And yes, torque converters are rated with a given stall speed, with modern converters approaching 1:1 at the stall speed before locking. There is a range of ratios that the torque converter operates in, with lock-up being 1:1. Anything not 1:1 results in some amount of torque multiplication, which is constantly changing. My example was that even with a miniscule amount of torque multiplication, the apparent gearing is greater than the manual's first gear ratio. Even with pumping/efficiency losses, the automatic's first gear would provide greater force than the manual.

Since I guessing you didn't like Wikipedia as a source, here's another "Typical stall torque multiplication ratios range from 1.8:1 to 2.5:1", and another "Torque multiplication rapidly decreases until it reaches a ratio of 1:1 (no torque increase over crankshaft torque.) A typical torque converter will have a torque multiplication ratio in the area of 2.5:1"

You missed it in the original post, so I'll say it again: regarding the graph, it's probably best to ignore first gear. I said this because there's no way that I know of to quantify when lock-up happens. True, the rest of the chart didn't take into account any losses (which I noted), please see this post for one that does. Neither chart is factoring in any torque multiplication at any point. They are both based off of the published gear ratios, tire height, and engine torque from here. The second graph has the engine output at 95% on the automatic, to simulate the automatic's lower efficiency.

Also according to Wikipedia (and a dead link to ZF's website) the ZF8HP70 (which is stronger than the Jeep's auto) weighs 192 pounds. I can assume the Jeep's 8HP50 is not any heavier, which is way lighter than I expected. This doesn't include the transmission cooler/lines/fluid, but I'm not sure the auto's weight penalty is as much as we expected.

Your chart shows torque multiplication going on in all gears at all RPM. It's literally just the gearing multiplied by a scalar for torque multiplication.....

Also, Stall speed is not where they go 1:1, stall speed is max multiplication. They go to 1:1 fairly shortly thereafter.

Edit: You do understand that torque multiplication and an effective gearing change would be the same thing, right?

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[AnnDee4444]

Here's how those charts were made. I'm starting with these known values: The 3.6 produces 260 lb.ft. @ 4800 RPM, with a 5.13:1 first gear, a 4.1:1 differential ratio, and 33" tire diameter. Also, it turns out I lied: I did factor in a 17% drivetrain loss on all numbers, along with a 1" tire sag. Still didn't account for torque multiplication from the torque converter, and I stand by my statement about ignoring first gear. Also, even if I am way off on the Y scale (like if there's only 0.5" of tire sag or 50% drivetrain loss), it's a relative factor that's applied to all the data and doesn't favor one or the other.

5.13 x 4.1 = 21.033 overall ratio
21.033 x 4800 = 228.2128 RPM @ the axle

33" x pi = 103.6726" tire circumference (aka distance traveled per revolution)
103.6726 x 12 = 8.63938' tire circumference
8.63938 x 228.2128 = 1971.617' traveled per minute
1971.617 / 5280 = 0.373412 miles traveled per minute
0.373412 x 60 = 22.40474 MPH in first gear @ 4800 RPM (This is the X axis)

260 x 21.033 = 5468.58 lb.ft. at the axle
33 / 2 = 16.5" tire radius
16.5" - 1" = 15.5" tire radius accounting for sag
15.5" / 12 = 1.291667' tire radius accounting for sag in feet
1.291667' / 5468.58 lb.ft. = 4233.739 pounds of force at the tire
4233.739 x 0.83 = 3514.004 pounds of force at the tire accounting for drivetrain loss (This is the Y axis)

Do this for every 100 RPM between 1000 RPM & redline using the torque values published here, and then again for every possible gear ratio for each transmission, and you too can make this exact chart yourself.

Just to double check, here's the 3514 pounds of road force peaking at 22.41474 MPH in first gear.

 

[AnnDee4444]

Your chart shows torque multiplication going on in all gears at all RPM. It's literally just the gearing multiplied by a scalar for torque multiplication.....

No, it's engine torque multiplied by gearing, with RPM adjusted to MPH and lb.ft. adjusted to pounds at the road by calculating the tire's lever arm.

Also, Stall speed is not where they go 1:1, stall speed is max multiplication. They go to 1:1 fairly shortly thereafter.

Ok, I'll admit I'm not an expert on the exact terminology. This still has little effect after first gear, which is why I said to ignore it.

Edit: You do understand that torque multiplication and an effective gearing change would be the same thing, right?

Yes.

 

[PatrickR]

No, it's engine torque multiplied by gearing, with RPM adjusted to MPH and lb.ft. adjusted to pounds at the road by calculating the tire's lever arm.

Ok, I'll admit I'm not an expert on the exact terminology. This still has little effect after first gear, which is why I said to ignore it.

Yes.

Ok, first, sorry- I reread what I wrote and I think I came across rather rude.

Second, what are you trying to show/prove?

 

[AnnDee4444]

Ok, first, sorry- I reread what I wrote and I think I came across rather rude.

Second, what are you trying to show/prove?

That the automatic (even with the engine output reduced to simulate additional drivetrain loss), puts more force to the ground than the manual for the majority of speeds. More force transmitted to the ground should equal greater acceleration (not accounting for weight, shift times, clutch dumping, torque converter flashing, etc.). It's gearing vs. gearing, multiplied by the engine torque.

 

[Toycrusher]

I probably have no right to post here, but the 6 speed is better than most and no amount of transmission intelligence can replace that special connection between man and machine you get with a three pedal setup

 

[AnnDee4444]

I probably have no right to post here, but the 6 speed is better than most and no amount of transmission intelligence can replace that special connection between man and machine you get with a three pedal setup

I totally agree.

At least until everything goes all electric... then I'm undecided. Direct drive has got to be more responsive than anything that has to shift gears.

 

[txj2go]

Most of my driving life I've driven manual transmissions. When I bought my Jeep I kept my daily driver which is manual. But my Jeep is automatic. I bought it to do trails and I didn't want to be on a steep trail trying to juggle a clutch pedal.

 

[McKenzie]

I probably have no right to post here, but the 6 speed is better than most and no amount of transmission intelligence can replace that special connection between man and machine you get with a three pedal setup

this whole thread is a 'vinyl or digital' debate - 2 groups just talking past each other.

i can't argue that the auto isn't faster, more economical, easier to drive, and more available (on the lots and across powertrains). I didn't choose the 3.6 - i love the idea of the 2.0 and the diesel. But i knew i would hate having an auto (although sometimes it would be convenient). I chose the manual because i thought it was awesome (similar to my choice of a 2 door). Was it the 'best'. many will say no. Would I like a JL with a 392? In theory, yes - BUT, I want a 2 door with a manual, so as I told my brother-in-law, I'll take my hemi in a challenger (also 2 door with a manual).

In the end, you just need to be honest with yourself - will you be happy with an auto? I won't. I would be disappointed every time i hopped in the driver's seat. I know because I went through this with my wife's previous car. I took the other ('my' car) just for the sake of driving the manual. The auto is great, and there are a lot of other great options with it (2.0/diesel/392/etc) that i would have considered if available with the manual. But this was my deal-breaker. Manual or bust. Forever (...until I change my tune)

 

[01tj]

How well does the auto do when holding back compared to the manual? I've always liked driving manual transmission-equipped vehicles but one of the biggest advantages has been the ability to put it in 1st gear at the top of a steep snow hill or a muddy trail and let it creep down. Even the duel clutch equipped cars I've driven would match that.

 

[Toycrusher]

How well does the auto do when holding back compared to the manual? I've always liked driving manual transmission-equipped vehicles but one of the biggest advantages has been the ability to put it in 1st gear at the top of a steep snow hill or a muddy trail and let it creep down. Even the duel clutch equipped cars I've driven would match that.

It seems the 8 speed has the manual whipped in just about any performance category. 6 speed wins in emotional connections only. And a Jeep is very much an emotional thing, therefore Jeeps and Manuals mesh well

 

[01tj]

It seems the 8 speed has the manual whipped in just about any performance category. 6 speed wins in emotional connections only. And a Jeep is very much an emotional thing, therefore Jeeps and Manuals mesh well

Does it hold back?

I know autos have come a long way and performance-wise they seemed to have pulled ahead in most vehicles. I know guys who complain about shift feel and pedal placement but I've always driven a stick in pretty much every vehicle. I thought it made my 2.5L TJ fun to drive and heel-toeing that thing really felt like an accomplishment lol.

 

[PatrickR]

That the automatic (even with the engine output reduced to simulate additional drivetrain loss), puts more force to the ground than the manual for the majority of speeds. More force transmitted to the ground should equal greater acceleration (not accounting for weight, shift times, clutch dumping, torque converter flashing, etc.). It's gearing vs. gearing, multiplied by the engine torque.

Ok I see what you're trying to do. You need to compare through theoretical shift points. Comparing gearing only isn't going to show what you'd need to show. Then, you'd need to account for a bunch of other variables.

I'll take the (limited) mag tests and person experience...

Of course, drive what you like. Subjective experience kind of trumps everything else on these kinds of purchases.

 

[Toycrusher]

Does it hold back?

I know autos have come a long way and performance-wise they seemed to have pulled ahead in most vehicles. I know guys who complain about shift feel and pedal placement but I've always driven a stick in pretty much every vehicle. I thought it made my 2.5L TJ fun to drive and heel-toeing that thing really felt like an accomplishment lol.

Personally, geared right, I prefer climbs and descents in a manual. Once the clutch is out, the tires are turning and you can focus on other things. Need a little more wheel speed? Give it a little more gas. The 3.6 has enough torque (well, with a Centerforce clutch for sure) to push up against a wall and have the four tires spinning slowly without stalling.

In an auto, you are playing a dance with the throttle, trying to maintain enough pressure to not roll backwards yet not give it to much throttle where the converter catches and you jump forward.

 

[JayJay]

Does it hold back?

Yes.

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