So you wanna put big tires on your 2.7 powered truck

Well, technically there’s less “loss” in a manual transmission. However, you’ll no longer have that torque converter to help you put around at low speeds, nor aid in torque multiplication.
I’m in a 3rd gen v6 manual, and rock crawling in the 3.5l has really made me wish i had that torque converter.

What’s the numerical gear difference? Most 4speed autos are effectively a 5 speed minus 1st, ratio-wise.

 

The mt has to be better. I'm on stock 4.10s with heavy (50lbs per) e range 235 85s. I also carry around some weight and my truck has 234k on it now. I still have to down shift to 4 for longer moderate climbs, and I can pull steep in 3rd. Just have to make sure you're planning ahead with gear selection and can't be afraid to wind her out. 4k plus rpms in 3 for the win on steep.

The only place I have ever held up traffic was on steep windy roads in Colorado. The turns were so tight I couldn't run high enough rpms to really get going in second. Have to slow down to ten or fifteen mph for the hairpin and then I'd have to start all over again in first.

 

Yea. I'm guessing the torque converter adds no more than 44%. So I think in most gears, the manual is still better. Also, the torque converter locks in 3rd and 4th.

5-speed manual:

1st - 4.31
2nd - 2.33
3rd - 1.44
4th - 1.00
5th - 0.79

4-speed auto:

1st - 2.804
2nd - 1.531
3rd - 1.00
4th - 0.705

 

You definitely have to drive it like a racecar. I will downshift into 3rd before I even get to the bottom of the proceeding hill so I'm already on the pipe as I get to the uphill. If you wait until you start to lose speed, it's too late.

 

What tires are you running?

 

ST MAXX 255/85/16....10-ply. I also probably had an extra 600lbs in armor and a cap.

 

I can attest that 5spd, 4.88s, armor, LCE Pro clutch, rear lunchbox locker, and 255/85 r16 KM2s is a killer combo in a 2.7 AC! Even with a few extra pounds of camp gear in the bed. Low speed crawling was easy, little gas or clutch inputs.

Now, with the exact same config, take away the locker and gears, it wasn't that great, but bearable. I had to be quick on the clutch, always use low range, and bump things harder. More gas, more clutch.
Take away the LCE clutch and it was even worse! All the gas because clutch was burnt by yours truly.

Mind you, I'm lumping on/off road together in my statements.

We'll see how this setup likes 35s real soon like!

 

How much extra junk you packing?!

 

Last weekend I drove my pop's '14 DCSB PreRunner 2.7L with the 4spd Auto and 265/75/16s, and it was a complete dog compared to my 09 2.7L 5spd with 295/70/17s and 5.29s. Mind you, i've got heavy cooper st maxx on my truck 66lbs each, and a full set of aluminum skids, steel sliders and steel bumper. I was really surprised my 5spd felt way peppier than his truck. Figured i'd throw it out there for reference. The auto makes the truck a whole different animal

 

The auto must be just a damn turd. It either needs over-gearing beyond the MT, and/or a better torque converter. I'm gonna say no one makes the latter, so 5.29s for the auto and 35s?

 

I believe IPT makes upgraded transmissions and converters

 

https://www.importperformancetrans.com/index.php?l=product_detail&p=1861

https://www.importperformancetrans.com/index.php?l=product_detail&p=4341

 

Well how bou dat!? You auto folks have options.

 

Ok, so you’d probably have a more powerful launch with the manual — though with the torque converter, you get the benefit of not worrying about clutch wear at low speeds.

However, if you consider the 4speed auto as a five speed minus 1st, i’m not sure your highway performance is really going to be much better — unless there’s a /lot/ of parasitic loss through the automatic

Maybe a high-spool torque converter would help “launch” it. — though that will reduce your downhill engine braking capabilities

And i guess an important question is, what is the automatic’s rear end gearing compared to the m/t?

 

Auto gearing is 3.90 or 3.91 I believe. I know that a 2nd gen 4 cyl MT is stock geared at 4.10.

EDIT: I imagine any and all parasitic loses in both trannys are through the flywheel and converter first and foremost. But lightweight flywheels are poo off road is my understanding

 

2nd gen 4 cyl automatic 4x4 should be 4.10 gears. The engine just isn't made for performance and when you add weight and bigger tires it definitely takes a hit and can't maintain OD on the highway with hills.

 

I agree. I'm cautiously optimistic that it will be better on the hwy. But it should be about 13% better based on overdrive ratio. Where I think it will be a lot better is on steep hills. With the auto, the jump between 2nd and 3rd is huge. If 3rd isn't enough, 2nd tends to be overgeared. So you're screaming up hills at only 45mph. With the manual, there's another gear between those. So hopefully 3rd on the manual will be a good gear to pull up some of the bigger hills and maybe I'll have a shot at keeping up with traffic.

Yea, I don't really know much about it. My truck is currently like a boat though. I have to stay on the gas down even the biggest hills or I will come to a stop.

I've been comparing anecdotally with people that have the same rear end ratio as me (4.88). I think in 2014, both the manual and auto came with the same rear gear ratio (4.10). I've since changed mine obviously.

 

Should, but they aren't 4.10.
Don't discount that the 2TR isn't made to perform. It'll rev and bounce limiter all day. Slap a header on and enjoy life.

 

The 2.7L auto comes with 4.10 gear on the 4x4 and prerunner.

 

That's right, I was thinking 3rd gens. My bad.