Swede

So the time has come to do a gear swap but I can't decide on the 4.88's or 5.29's.

Here's what I got:

My initial thought was to go with 4.88's and here's why:
3rd gen, 5-speed, and 35's (for most of the year, and 32" studded tires in the winter)
Daily commute to work of about 10 minutes each way at highway speeds.
Off-roading ranges from steep deactivated logging roads to sand to mud.

However, lately the wife and I decided to by a 19' travel trailer for camping with the kids so I'm now leaning towards the 5.29's.

My only concern is the fact that, come winter time and I change over to the studs, I'll be revving higher than I should be, and I run these tires for anywhere from 4 - 5 months of the year.

So let's have you opinions please!!! What should I do???

SCToy

I'd not like running such high RPMs in the winter on a cold motor, but that's just my opinion.

I actually found that 35s on 4.88s to be to my liking. Speedo was dead on in my 81. I don't think it would be fun pulling a trailer though. 5.29s will probably be nicer offroad too.

waskillywabbit

iTrader: (-1)

What gears now?

5.29s will rev high with 32s for sure.

:wabbit2:

scuba

You could get away with 4.88's since you have a 5 speed.
However, since you'll be towing a trailer, I'd definitely go with 5.29's.

Plug your specs into the Grimm Jeeper calculator and see exactly where you'll be revving.
For reference, on 5.29's and bald 33" KM1's I was revving at about 3250-3500. So expect to be in that same general range.

Swede

I have the 4.10's.

JBurt

At what speed?

scuba

70

Swede

As it is now, (4.10's and 35's) at 65mph (GPS) and in 4th gear, I'm turning 2750rpm. 5th gear had me at 2250rpm. Anyone got a link handy that has the ratios in a 5-speed?

andrewflores17

http://http://www.grimmjeeper.com/gears.html

scuba already hooked it on up

410s with 35s i couldnt even shift into 5th without slowing down id go 4.88 thier isnt a middle gear between them and 5.29 the thing is you do have a trailer but how much are you realy gona be pulling that compared to DD and whelling

scuba

...

Swede

Missed it... my bad, thanks!

ZUK

iTrader: (1)

hey Swede-
I broke it down in 10% gear changes below using a couple of obvious gear numbers...


4.10 = 2250rpm
8.20 = 4500
as shown above ...100% gear change results in 2250 rpm change.....
divide each by 10...that means every 10% gear change results in 225 rpm change for you.

10% ....456 gears = 2475
20%....488 gears = 2700
30%.....529 gears = 2925

within about 1% accuracy anyways. 2925 ain't that bad.

ZUK

iTrader: (1)

Here's another crazy way to look at your 4th gear verses the 5th gear change....

4th = 1 = 2750rpm
5th = .85 = ??
6th = .50 = 1375rpm

6th gear does not exist in real life but the numbers are easy to see by comparing....
it's east to figure it in your head...a .50 overdrive which is a doubling of the speed or a halving of the rpm....6th gear...1375rpm change for "50 ticks" which means each tick is worth 1375/50=27.5 rpm....it takes 15 ticks to get from 4th gear to 5th gear...so 15 ticks is 15 x 27.5 = 412 rpm

At your gps 65mph in 4th at 2750....
and then your drop it in 5th means 412 rpm less.....rpm's now read 2338. That differs a little from the 2250 you noted in 5th gear but your speedo readout is not digital so that read error can happen with an analog display.
Time for a glass of Green Fin.....maybe a bottle.

Swede

Zuk, you can have the Green Fin ... I'll have an aspirin! Took me around 15 minutes to get my poor head around your numbers but I think I see what you're saying now.

Going by the figures I had input into the link you guys gave me, and in 5th gear, this is what I came up with:

4.10's & 31's (Stock Gears & Tires) = 65mph @ 2426 rpm

4.10's & 32's (Studs) = 65mph @ 2351 rpm ( -75 rpm)
4.10's & 35's (M/T's) = 65mph @ 2149 rpm (-277 rpm)

4.88's & 32's (Studs) = 65mph @ 2798 rpm (+372 rpm)
4.88's & 35's (M/T's) = 65mph @ 2558 rpm (+132 rpm)

5.29's & 32's (Studs) = 65mph @ 3033 rpm (+607 rpm)
5.29's & 35's (M/T's) = 65mph @ 2773 rpm (+347 rpm)

For everyday daily driving it looks like going with the 4.88's is a no-brainer as it's pretty close to the stock rpm's. However, it sure would be nice to have a little extra grunt that the 5.29's may provide while pulling the trailer, as well as having the lower range off-road! Remember too that when camping season comes, I'll be running the 35's only. I guess now what I'm asking is, if I run the 5.29's with the 32" studs at over 600rpm higher (at 65mph), can I live with the extra fuel consumption (if it's noticeable), noise, and general wear and tear? Will running 607rpm higher be too much?

zacmax

just for conversation wise, i am running 35's and i have 4.88 in it, i enjoy the high way speed power while still being able to tow effectively(i have supercharger also, so that helps)

andrewflores17

one word NICE

Swede

That's cheating... you're not allowed to play!

scuba

These engines LIKE to rev.

3000-3500 at highway speed is nothing.

gk5

At the cost of fuel consumption

scuba

RPM isn't the only thing that has a role in MPG.

Geared too high and don't have the power to make that hill? Lug the engine and give too much throttle position and you'll get worse MPG then I.