What gear ratios did these Jeeps come with?

tjkj2002 · **Posted:** Thu Dec 11, 2014 8:44 pm

jrsavoie wrote:

I always base everything on the 6.5 diesels we have. BAsed on the fuel mileage we get with them, a tiny little thing like these Jeeps should be capable of far better mileage than 25 mpg. A Suburban is about 3 times the size and can still get 20 mpg with half of what I invested in extras for the Jeep.

I got 18 mpg regularly with our K3500 crew cab long bed single rear wheel truck, 4:10 gears with 5 speed NV4500, before I added the ladder rack and tool boxes. Now it gets about 16 mpg.

With the 1996 K1500 Suburban 3.42 gears we can load the whole family and still get 18 mpg.

The CRD KJ is a 4300lbs brick so a average of 25mpg is fantastic,even though the gasser versions can achieve a few less so it's not really that great.

These aren't a 3000lbs FWD car.

rancherman · **Posted:** Thu Dec 11, 2014 10:27 pm

thermorex wrote:

gmctd wrote:

True - but the KJ FSM lists 3.55's as available, so I had tho't to search the boneyards for other late DCJ Corporate 8-1/4" axles, such as KJ's, GC's, Wranglers, RAM 1500's, etc - early KJ 3.55 would have been direct diff assembly-swap, the others would have been R&P swapout, all cheaper than across the parts-counter

It's still in the back of my mind to research and accomplish, but it's becoming more and more of a pipe-dream - sigh............

Too bad you can't just throw some 31s on it just to see the mileage. I guess 31s with 3.73 would best simulate the 3.55 gear ratio with stock tires, this without calculating anything.

the 31's would get you pretty close to the 3.55's for engine rpm... but at the same time take more fuel to accelerate and maintain speed.. Probably a 'wash' here for economy's sake.

3.55's I've found are 550 for the pair... for anyone considering.. http://www.jeep4x4center.com
For me, I'm happy as a clam with the 25-27 mpg's I'm currently knocking out with winterized fuel. Neighbor's 3.7 gets 18-20, and even with TODAYS fuel prices, I am still 1.5 cents per mile cheaper to run the crd.

jrsavoie · **Posted:** Fri Dec 12, 2014 7:09 am

thermorex wrote:

25 vs 18 is still a big difference. If the 2.8 engine would be in another vehicle, more aerodynamic, I bet will get 30mpg. I mean honestly, it's a jeep, not a small Vw tdi.

I do get about the same mileage as you do when driving around the town. If I go hundreds of miles distance, I get 27-30+, depending on how hard I step on the pedal.

I can load the Jeep in the back of the truck and still get 16 MPG.

The nearest town here is 7 miles one way. Unless you consider L'Erable a town - that's 2 miles - 20 houses, a church, tavern, 5 stop signs and graveyard.

thermorex · **Posted:** Fri Dec 12, 2014 9:16 am

jrsavoie wrote:

thermorex wrote:

25 vs 18 is still a big difference. If the 2.8 engine would be in another vehicle, more aerodynamic, I bet will get 30mpg. I mean honestly, it's a jeep, not a small Vw tdi.

I do get about the same mileage as you do when driving around the town. If I go hundreds of miles distance, I get 27-30+, depending on how hard I step on the pedal.

I can load the Jeep in the back of the truck and still get 16 MPG.

The nearest town here is 7 miles one way. Unless you consider L'Erable a town - that's 2 miles - 20 houses, a church, tavern, 5 stop signs and graveyard.

obviously you kind of hate the jeep, lol. Which is maybe normal for a person that drove big SUVs like suburban. Take a longer trip, 200+ miles, drive easy, at around 70-ish, have at least 45psi in the tires and it's likely to get 30-ish mpg. You won't get that in suburban. Or, if you really like suburban, look into a natural gas conversion for it, a kit starts from 1000-ish and can go 6000+ for an epa approved one. It can give you 30%+ fuel economy overall and it works in tandem with diesel injection, it just adds a bit of natural gas to the air through intake, increasing mpg. This way you drive what you want with greater fuel economy.

jrsavoie · **Posted:** Fri Dec 12, 2014 10:21 am

thermorex wrote:

jrsavoie wrote:

thermorex wrote:

25 vs 18 is still a big difference. If the 2.8 engine would be in another vehicle, more aerodynamic, I bet will get 30mpg. I mean honestly, it's a jeep, not a small Vw tdi.

I do get about the same mileage as you do when driving around the town. If I go hundreds of miles distance, I get 27-30+, depending on how hard I step on the pedal.

I can load the Jeep in the back of the truck and still get 16 MPG.

The nearest town here is 7 miles one way. Unless you consider L'Erable a town - that's 2 miles - 20 houses, a church, tavern, 5 stop signs and graveyard.

obviously you kind of hate the jeep, lol. Which is maybe normal for a person that drove big SUVs like suburban. Take a longer trip, 200+ miles, drive easy, at around 70-ish, have at least 45psi in the tires and it's likely to get 30-ish mpg. You won't get that in suburban. Or, if you really like suburban, look into a natural gas conversion for it, a kit starts from 1000-ish and can go 6000+ for an epa approved one. It can give you 30%+ fuel economy overall and it works in tandem with diesel injection, it just adds a bit of natural gas to the air through intake, increasing mpg. This way you drive what you want with greater fuel economy.

If we went on a longer trip, we would definitely take something else besides the Jeep. LOL

I couldn't stand the pain of riding in the Jeep that long. My legs most everything else hurts after riding in the little box.

Are there any other big guys here that are comfortable in the Jeep? I'm not all that big but I can not sit upright in the Jeep. The doors hit me in the shoulders, so I have to lean sideways, no matter which seat I sit in. And the leg room sucks. I have to straighten my legs out every so often or they lock up. I have a heck of a time doing that in the Jeep.

gmctd · **Posted:** Fri Dec 12, 2014 12:18 pm

jrsavoie wrote:

If we went on a longer trip, we would definitely take something else besides the Jeep. LOL

I couldn't stand the pain of riding in the Jeep that long. My legs most everything else hurts after riding in the little box.

Are there any other big guys here that are comfortable in the Jeep? I'm not all that big but I can not sit upright in the Jeep. The doors hit me in the shoulders, so I have to lean sideways, no matter which seat I sit in. And the leg room sucks. I have to straighten my legs out every so often or they lock up. I have a heck of a time doing that in the Jeep.

Did you miss my post vis a vis the this-century D-max\Suburban conversions, or just not interested?

jrsavoie · **Posted:** Fri Dec 12, 2014 12:25 pm

gmctd wrote:

jrsavoie wrote:

If we went on a longer trip, we would definitely take something else besides the Jeep. LOL

I couldn't stand the pain of riding in the Jeep that long. My legs most everything else hurts after riding in the little box.

Are there any other big guys here that are comfortable in the Jeep? I'm not all that big but I can not sit upright in the Jeep. The doors hit me in the shoulders, so I have to lean sideways, no matter which seat I sit in. And the leg room sucks. I have to straighten my legs out every so often or they lock up. I have a heck of a time doing that in the Jeep.

Did you miss my post vis a vis the this-century D-max\Suburban conversions, or just not interested?

Apparently I missed that post. Is it in this thread? but I have seen it now.

ACtually my favorite Suburban body style was the square body that ended in 1993? You could stack a lot more sheets of drywall or plywood in one of those. But I do like some of the modern day amenities

jrsavoie · **Posted:** Fri Dec 12, 2014 12:35 pm

minisub wrote:

gmctd wrote:

....

but I had wanted to shove a set of 3.55's into the 8-1/4" axles to see if that was the cure - avg 20mpg is good, but seems like the li'l puffer could do much better with reduced rpm across the board.....

Interesting thought. But the math, oh the math. Assume R&P set at $600 and a 5% increase in MPG in direct proportion to ratio difference. Further assume $4 fuel and 25 mpg base and it would take 75k miles to break even! Even at a 20 MPG base it would take 60k miles....

I put 800,000 miles on my last truck. That gives a lot of pay off time. Not to mention the extended life on the engine by running at lower RPM's for the rest of it's life

gmctd · **Posted:** Fri Dec 12, 2014 2:29 pm

jrsavoie wrote:

gmctd wrote:

Did you miss my post vis a vis the this-century D-max\Suburban conversions, or just not interested?

Apparently I missed that post. Is it in this thread? but I have seen it now.

ACtually my favorite Suburban body style was the square body that ended in 1993? You could stack a lot more sheets of drywall or plywood in one of those. But I do like some of the modern day amenities

Yep - I still have my first Diesel, the last of the 80's 6.2L square crewcabs ('89), which I jacked up, converted from 2WD SRW to 4WD DRW, Turbo400 with auxiliary Brownlite 3-spd overdrive box to get the rpm's down with the 4.10 final drives
- into which I loaded a '95 GMC 6.5L turbodiesel (my sig) replete with manual trans PCM
- I later removed the way-heavy Brownlite, replacing the T400 with the '95 4L80E 4-spd\o'drive auto box, replacing the manual PCM with the 4L80E PCM
- hadta use the '91 Suburban EFI instrument cluster because the '95's had electronic speedo, also designed the electronic interface for the '91 electronic tachometer
- solved the A\C dilemma by using the evaporator case from the S10\S15 blazers to clear the turbocharger, so it is still air conditioned, upgraded to R134 by using the '91 refrigerant hoses (plastic inner liner) and R134 expansion valve

Cranked it up last week, after sitting there almost 5yrs - lit right off after whacking the then-new shuttle-type lift pump to get it started and bleeding the filter cannister - never missed a lick, smooth as rocks in a cement mixer - which, as you know, is normal for an EFI 6.5L TD - 4L80E shifted right into gear, pulled in R and D, as normal
- good truck, still

minisub · **Posted:** Fri Dec 12, 2014 8:08 pm

jrsavoie wrote:

minisub wrote:

gmctd wrote:

....

but I had wanted to shove a set of 3.55's into the 8-1/4" axles to see if that was the cure - avg 20mpg is good, but seems like the li'l puffer could do much better with reduced rpm across the board.....

Interesting thought. But the math, oh the math. Assume R&P set at $600 and a 5% increase in MPG in direct proportion to ratio difference. Further assume $4 fuel and 25 mpg base and it would take 75k miles to break even! Even at a 20 MPG base it would take 60k miles....

I put 800,000 miles on my last truck. That gives a lot of pay off time. Not to mention the extended life on the engine by running at lower RPM's for the rest of it's life

Sounds like a good option for you. Randy's has the parts, and they cross to all other applications if you wanted to go scrapping as gmctd was planning to do.

For me, doing about 15k miles a year in the road salt capital of the world, I get vehicles to last about 15 years before they dissolve. That only got me about 200k on the '85 Toyota and the '95 Tahoe. I'm hoping metallurgy has improved and I do better with the two '06s.

What gear ratios did these Jeeps come with?

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