Outer Limits 4x4 Board

Idea for you all to think about. I'm building my buggy.(91 trooper 4 dr, back-halved w/ small deck) I have a dodge 2.5l front wheel drive engine and transaxle that I'm thinking of turning the PROPER way and using one of the half-shafts to power the isuzu 5 spd and diffs. Am I going to have to regear ( I was thinking of an SAS anyway) to get a reasonable highway rpm? example: 3.55's v 4.56's. The transaxle has a 3:55 .1 diff ratio lready in it so.oo...oo wich way do I need to go. I will be running 35's. Any Ideas, thoughts, facts?? Oh... and before you berate my mopar engine... its pushing 250hp/280lb/ft.

Trooper is a Jackaroo over here. What motor does it currently run?

The only way i can see you using an east-west motor in a north south position would be if you separated the motor from the box/transaxle, then ran it into your existing Isuzu box.

The way i understood your post, you want to essentially run an axle shaft from one side of the transaxle into your existing gearbox. Doing this in addition to running 35's, the gearing would be simply far too tall.

My tooper engine is toast. (2.8l v6) My math skills on this idea are giving me a headache. the way I see it is that the transaxle output is roughly 2/3rds slower than the engine rpm (3000 engine rpm = 1000 half shaft rpm) run that through the isuzu tranny and out to the diffs and..... now what? higher or lower gers to make everything run ok on the highway

ytzuzu wrote:My tooper engine is toast. (2.8l v6) My math skills on this idea are giving me a headache. the way I see it is that the transaxle output is roughly 2/3rds slower than the engine rpm (3000 engine rpm = 1000 half shaft rpm) run that through the isuzu tranny and out to the diffs and..... now what? higher or lower gers to make everything run ok on the highway

Numerically lower ratio needed in buggy's final drive to make up for the ~3:1 the FWD transaxle diff is giving you.

If the buggy is currently (or anticipated to be) running about 4.5:1 you would need to effectively go back to 1.5:1 in the buggies final drive (with standard tire), OR take the tire size from the normal 28" or so to about 42" (with standard diff ratio), OR any intermediate combination of these. (ie 35" with 3.0:1 diff ratio) to level it out.

More numbers on actual diff ratios and anticipated tire sizes would help finalize a few calculations for you....

Be aware that the input shaft of the buggy transmission is unlikely to be strong enough to take the extra torque you will be feeding through it.

ok. I'm running 35's with 4.56 diff ratios. I thought I would need to spin the buggy driveshafts faster to make up for the reduction in the transaxle. or am I thinking backwards. I've got an NV 4500 I can slip in there. would be cool though... 50 forward gears...!

engine 3000 rpm (a)
transaxle out 1000 rpm (b)
transmission out (top gear) 1000 rpm
wheel rpm 220 (after buggy diff).(c)

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Wheel distance per revolution = 35"dia x 3.1415 = 110" (d)

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Total distance travelled in one minute = 220 (c) x 110" (d) = ~24000" , or 0.38 mile/minute (trust me on that one, have a calculator that does the conversion)

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0.38 x 60 (mins per hour) = 23mph

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So in summary, if you followed the logic in all that

23 mph at 3000 engine rpm (a) in top gear of the transmission with 35" (d) tires and a 4.56 diff (c) connected to a transaxle with ~3:1 diff (b)

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options

42" tires would give you 27.5 mph at 3000 engine rpm
42" + (D44) 3.54:1 would give 36 mph at 3000 rpm
42"+ (D44) 3.08 would give 41 mph at 3000 rpm


Basically reving it tits off with any realistic parts combinations, not to mention the stress on the input shaft of the transmission. All in all not a sound idea for a road runner/rockcrawler.