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Old 07-01-2013, 10:22 PM
razorgrill razorgrill is offline
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Join Date: Jan 03, 2010
Location: Tucson, AZ
Posts: 66
Question V8 or Straight 6?

What would you prefer and why?

I am leaning toward swapping the V8 for a 6. I really miss the Six I had in my F150.

Pros/Cons - Lemme have em!

Also, if anyone has a 6.. down for a V8 trade?
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Old 07-02-2013, 01:06 AM
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Carnuck Carnuck is offline
 
Join Date: Feb 12, 2011
Location: Lynnwood, wa
Posts: 6,309
Go stroker or at least a 4.0L and EFI. I recently found out that the '00 and newer intake may clear the OEM brake booster and master instead of going Hydroboost.
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Old 07-02-2013, 10:23 AM
twmattox twmattox is offline
350 Buick
 
Join Date: Feb 24, 2003
Location: Indiana
Posts: 1,269
I have debated it a long time. High output 4.0 with overdrive trans and properly geared axles would be quite nice. But, not sure it would give any real MPG results. My wife's Grand Cherokee (with a 4.0) got around 16mpg and it was a decent bit lighter than my Grand Wagoneer (and I get around 14mpg).
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'83 Scrambler (CJ-8) / 258 / T-5 / D-300 / DANA 30-AMC20 (3.31)
'88 Grand Wagoneer (SJ) / 360 / TF727 / NP229 / DANA 44 (2.73)
'05 Wrangler Unlimited (LJ) / 4.0L / NSG 370 / NV231 / DANA 30-44 (3.73)
'15 Wrangler Unlimited (JKU) / 3.6L / 42 RLE / NV 241 / DANA 30-44 (3.73)
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Old 07-02-2013, 11:37 AM
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Carnuck Carnuck is offline
 
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Location: Lynnwood, wa
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You DON'T want the Grand Cherokee trans. It's a 904 with O/D and probably weaker than the TH400/Dana 20 sleeve (definitely weaker than the XJ AW4) The way it's set up, it's inefficient and wastes power and fuel. High stall converter to overcome the tall first gear ratio to get moving. It turns more of the takeoff energy into wasted heat than an AW4 does.
I'm getting 17 mpg hwy with a load (14 towing an SX4 at 70 mph) out of my Comanche with 4.0L and AW4/NP242. Gearing for the tire size and load is very important with the 4.0L combo. When I got back, I switched out the 235/75/15 tires for the 33/9.50/15s and power/economy dropped noticeably. That's with a 200,000 mile motor and 3.73 gears. I figure for running empty, it would be back to 17 mpg highway and be perky enough, but I work my rigs so 4.10 is what it should have with my tire choice.
This is with Renix EFI. With HO I might drop the gear ratio slightly more because while they used the same profile cam (at first), Jeep retarded the timing of it (about 10 degrees I recall reading) to do away with the knock sensor and EGR valve. That pushes the power band curve up the RPM scale a few thousand and increased the HP at the same time, but the increase was partially because the curve tops at a higher RPM.
When Jeep went from Renix to HO they also changed the overdrive ratio from .70 to .75 on AW4 automatics and possibly AX15 standard transmissions as well. I know they did it with the 4 cyl's AX5 trans.
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Old 07-07-2013, 10:15 PM
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FSJunkie FSJunkie is offline
The Nigel Tufnel of the FSJ world.
 
Join Date: Jan 09, 2011
Location: Not The Hot Part, Arizona
Posts: 3,800
Early 1993 Grand Cherokees had the AW4. Late 1993-on had the 42RE. I have no complaints about that trans so long as idiot dealer service departments haven't screwed it up. They would often misadjust the TV cable or bands and ruin the unit or run Dexron in it thinking it was an AW4 even though is uses ATF+.

1st gear is actually 2.74, which is lower than 1st on the THM400 and TF727 of 2.45, and overdrive is .69.

My 4.0L ZJ has less than 1000 miles on it. Just for meandering around town it has the gearing to pull off the line quickly, but it's not the instant head-snapping torque a V8 gives. On the highway it feels powerful because the pedal doesn't have to be pushed down very far to cruise, but come to a hill or go to pass someone and your foot sinks quickly.

The power in a 4.0L doesn't kick in until 3000 RPM and pulls hardest at 3500, so you have to ring down to the engine room for another gear and rev the piss out of it before you do anything antsy. Do that, and the power is decent, but the sound of an I6 at 4000 RPM fighting against 4500 pounds of Jeep is not a reassuring thing. You can tell it is working hard and doesn't like it.

Perhaps I'm spoiled by learning to drive in a 360 Wagoneer, a 327 Rambler, and a 5.9 Dodge truck. I'm used to just shoving my foot down and as long as the engine is between 1500 and 4000 RPM, I'll rocket forward with no complaints from the engine. It seems to like it, actually...

I've noticed on every EFI car I've driven that pushing the throttle past 1/2 when already in the engine's peak power band doesn't do much more good compared to the same operation a 2bbl or 4bbl carbureted engine. On them, the power doesn't even kick in until 1/2 throttle.
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Last edited by FSJunkie : 07-16-2013 at 09:58 PM.
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