LUVTruck.com

hey anyone know what exactly it would take for me to swap out my 4th gear for a custom machined gear with a different tooth count to raise my freeway speed.
1st-3rd are usually good for in town but 4th just doesnt make a big enough difference over 3rd for 70mph freeway driving.
i have access to a lathe and mill. would i just need to pull the 4th gear and machine a new one with a couple more teeth with the same pitch and depth?

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

4th gear is 1:1 and is a straight through connection, no gears. You'll have to change the ratio in the rear axle or find a 5 speed.

dang

having a 4x4 i cant really change the ratio without having issues unless i made a gear for both diff's.

i really need to get a 5 speed with a t-case. it seems like whenever i find a pup/trooper 5 speed trans its 2wd or the 4wd ones are 4 speed.
i need to make a pick-n-pull run.
from anyone on the forum who has made the swap how big of a difference does the 5th gear make to top speed and 60 MPH RPM? when im at 60 im usually around 4k RPM. it seems like it would be a great option to make highway driving more enjoyable.

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

A 4x4 Trooper or P'up with the 2.3L engine, '86 & '87 will have the 5sp, 5th gear is somewhere around .86:1 ratio, would drop the 4k down to about 3600.
You must be running about a 26" tire to pull that many rpm's at 60 mph, you can increase the tire size for better highway performance at the expense of power on the lower gears and not have to change anything but the speedo gear. I would try to borrow some larger rear tires & wheels for a test drive, then decide if the 5sp is the way to go.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

or both
sadly my tires arent even 26" pretty worn down 195/75R14's last time i checked they were approx 24.5" mayba a lil bigger. but not much over 25"

and being that 5th would be a "gear" gear and not a straight shot through the trans that would mean it could be modified to give me even better highway speed at the cost of slow acceleration to the top speed. even a change of one tooth would make a difference.

either way i need to do something!
i like to go fast its just my thing, i have been on dirtbikes since i was 4 i love haulin @$$, i make that luv do things it was never meant to do but it does it just fine.. it accelerates pretty dang good but the lack of top end speed is killing me.

sadly im the kind of person who can never just say "alright it runs good let it be" its "hmm... well it runs now, but... now it needs some boost, and a micro shot of nitrous to spool the turbo.... and some this and some that" i can never just leave it alone as is.

does anyone know what the actual redline is for the g180?? i know it stops making power in the 5k's but with a cam and such how far can you take them? mine has seen 6k on more than one occasion but its sketchy to wind that motor up that high as it is.

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

Buy bigger tires.

Bigger wheels and tires would help a bit. If you can find a set of newer fullsize chevy take off wheels that might be affordable and easy. If you have a 4:10 rear going from 195/75/14 to 235/75/16 your RPMs @ 60 would drop from 3395rpm to 2848rpm. You would feel the difference for sure. Take off wheels on craigslist in SoCal are pretty cheap and plentiful and they have 17's & 18's out there too.

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Three Amigos

pretty cheap up here too anywhere from $50-300 depending on condition
i have been looking for a set of escalade 17's or just about any of the newer 15-17" GM 1/2 ton wheels. just need my paycheck now

like these
http://portland.craigslist.org/nco/pts/2256861865.html

http://portland.craigslist.org/clc/pts/2255272570.html

or if i could afford it right now...
http://portland.craigslist.org/yam/pts/2250845987.html

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

The Escalade wheels with lo-pro tires might net out close to the same diameter as what you have now. The big meats might require some fender trimming. Your first selection might be the ticket.

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Three Amigos

yeah no way i could fit 39's without some serious hacking, a 32 rubbed my bed

the 17's were just an example of the style those tires are sadly tiny... a tire closer to the stock diameter would do pretty well i would think. anything from the 28-30" range Should work pretty well

it seems like my motor in 1st wants to spin my tires faster than the truck is willing to move from a stop as it is so adding a few inches of diameter to the tires might even it out a bit... the random "unintentional" burnouts might lessen a bit till i have the power and axle to roast a bigger tire as well

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

Alright. well its looking like the LUV is going to take a road trip this summer. Vancouver to Upton, Wyoming and back. about 2250 mile round trip.
even if hell did freeze over i wouldnt drive it there in its current state. TINY little tires, i need something much bigger if i am ever going to be able to stay sane driving that long.

Would a Set of 31's work well for non stop freeway driving? to keep the RPMs down.
i see cheap used sets of 31" tires on aluminum 6 lug wheels all the time. the little 25" tires on the luv now just dont cut it for highway driving.
im just not sure what size tires would be the best for highway driving. i would like to find something around 31" or so to lower rpm without being stupidly huge.. will i need a lift to clear 31's?

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

A 31" tire will probably rub in front with no lift & no fender trimming. A 31x10.50 (actually nearer 30.5" diameter) will run about 2750-2900rpm @ 60 mph depending on the tire pressure.
The stock 4x4 LUV tires were about 28", if you go much over that there will be a notable power loss.
BTW 4,000 rpm with a 25" (worn 195/75/14) tire is closer to 70mph than it is 60, I'm not sure how you calculated your speed at that particular rpm. Running a smaller tire than stock makes the speedo read faster than actual, larger tire reads slower than actual.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

it wasnt an exact reading just an approx since my speedo isn't working anymore i was going from memory. musta been when was trying to keep up with traffic as 70 mph and the 4k was scarred into my mind

I usually try to keep it around 3400-3600 on the freeway for the most part with the occasional 4k+ passes... sure it doesn't keep up with traffic but i usually keep pace with the semis and the occasional draft is helpful
so im looking for 28-29" tires & a 5 speed before june
a tranny with t-case is gonna be about 300 at picknpull so hopefully about 450-500 total for trans, wheels and tires.

the truck wont be loaded down, about 220LB of dirtbike, and maybe another 100- of gear & misc, plus myself and the girlfriend, hoping for 30+ mpg still going to cost $300 in gas
anyone i should stop and say hi to on the way thru Wa, idaho & montana?

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

Interesting you'd suggest that. As oldestisuzuist mentioned, the 5-speed final ratio is about .86:1. However, there's an IsuzuPup.com member with a 2wd who swapped out the 5th gearset from a pre-'86 transmission. Because the countershaft rotates at a different speed, using those gears gave him about a .78:1 overdrive. I believe the 4wd 5-speed is basically the same as the 2wd, except it has a T-case. So, in theory--you could use a 5-speed 4wd transmission from an '86-'95 P'up or Pickup, and swap the 5th gearset from an '81-'85 2wd transmission, and get a .78:1 overdrive. In theory. I say that, because I have not done it and have not seen it with my own eyes. The only person I know who did it has a 2wd.

Jack

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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.com
IsuzuPup.com

86-95 pup and atleast 86-87 trooper. k i can find one i believe. i can get a trans and t case for $300 so that will be something i invest in soon. im thinking if i do im going to have to do a full thread on the swap since it keeps coming up

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

It may have been mentioned earlier, but just to be sure: This will not be a bolt-in swap. The transmission (I'm told) is longer to accommodate 5th gear.

Jack

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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.com
IsuzuPup.com

yes i have read that also, i will cross each bridge as they come to me. i am wanting to do a build thread on it simply because of all the little modifications and odds and ends have been covered breifly and randomly all through the site but i havent seen a step by step swap with pics so i would like to make one for the other LUVers if anyone needs it.

either way that 4 speed is killing me since a lot of my driving is on the highway since i live about 3 blocks from the on ramp

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

just did the math.
all of this is with a 29" tire, 4.10 Rear end ratio [may be a couple mph off depending on tire wear, pressure etc]

Stock 4 speed @ 2800 RPM = 58.9 MPH

5 speed as they come with .86:1 5th
2800 RPM speed will be 68.5 MPH

with the 5th from an earlier pup 2wd with .78 ratio
2800 RPM speed will be 75.5 MPH

thats a big difference

is there anyone who can verify the different gearing for the earlier 2wd 5 speed 5th gear or anyone i should ask? that .78 5th would be perfect if it is correct

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

It doesn't really matter what the 5th gear ratio of a 2wd tranny is, to get that gearset swapped into a 4x4 5sp would be cost prohibitive even if you could find the parts. Decide what speed you want to drive then calculate what final drive ratio it will take to turn at or near 3,000 rpms (max torque) at that speed, otherwise the engine likely won't have enough power to maintain the desired speed. You can very easily get it geared so high that it won't maintain highway speeds in 5th gear, in part because your 4x4 is heavier and stands taller (read more wind resistance) than a 2wd, so it just takes more power.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

all the pups use the 14.5% O\D 2 or 4wd if they have the 5sp

the hard to find one is the isuzu car that is RWD it has the same 2wd trans as the 2wd luv\pups. just a different O\D

in my quest to re-bearing my 4wd 5sp trans,
ive found it would not be to hard to swap the 20~% car O\D to the 5sp 4wd trans.

the hard part would be finding the car trans, and if you want to run big tires the taller O\D would likely be over kill, possibly making less mpg with big tires. and dropping to 4th on grades that most would call flat land.

if i remember right all the Isuzu Impulse RWD cars have the same gearing even if not turboed.
the rear gear is an ODD 3.90 and the turbo models have a ""insane rare"" LSD diff.

i know the turbo parts fit the 2.3L but i don't know about the 1.8/1.9 possible? maybe a no-go?



in 1990 the Isuzu Impulse became a FWD car, so its gotta be from a pre 1990 model
most of the turbo models where around 87/89 or so

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86trooperT/D 2.2
84 L\B 4x4Diesel LS 2.2
84 S\B 4X4 gas rust bucket 1.9
86 L\B 4X4 gas 5 speed 2.3
the twins, 81 pup and 81 LUV both are diesel 2.2



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