What Gear Ratio (1 Viewer)

[yotarunner98]

Hey guys. Im in the middle of a SAS on my 4runner with a fzj80 axles front and back. I'm leaning towards running 4.88's with 36's (i have 3.4L auto (t-100 trans and tcase). I'll be doing a good bit of highway mileage which is why going 4.88's instead of 5.29's. Most of the off roading i do is mudding in the pine barrens of new jersey but I'm hoping to make it out to raush creek soon and anything else in the nj/pa/ny area i can get to. What do you guys think and what are you running?

 

[d0ubledown]

I had 4.88s on my 98 with 3.4 & auto on 315s. perfect match. 5.29s would be nice on rocky trails but would be spinning higher at freeway cruising speeds. go 4.88s.

interesting swap using the 80 setup with the t100 case. got build
pics?

 

[yotarunner98]

yeah right now it's on rightcoast but i'll probably be putting it on here or pirate when i get some time. i worked on it for a week straight last week doing a full trans/tcase swap and putting the 80 front axle in with radius arms, this weekend i'll be working on the panhard bracket, hopefully the oil pan if i can find one and finishing hooking up the trans/steering

 

[mmml4]

Very cool build indeed. I am doing almost the same build on my 99 4runner but instead of the T100 tranny/tcase I am using the one out of the Cruiser.

I will be running 35's and will need to do a gear change also. Please post the build as I would be interested in seeing how others do it.

Here is my build mmml4's 1999 4Runner Rebuild/Build-Up Thread - YotaTech Forums

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[ToyTec Lifts]

Most 80s guys do 4.88s when going to 35's it is the best ratio until 37s then most go to 5.29s. Also it really depends where you live high altitude 5.29 might be better. Good luck on your build

 

[3rdgenrunner]

i maybe wrong here but i have heard that if u run 5.29 with 35s it spins the same revs at hwy speeds as the stock 5speed idk if this helps but just thought i would put that out there

 

[yotarunner98]

i maybe wrong here but i have heard that if u run 5.29 with 35s it spins the same revs at hwy speeds as the stock 5speed idk if this helps but just thought i would put that out there

that depends on what the gear ratio was to begin with.... this is the way i'm breaking it down and let me know if this makes sense to any of you...

[(new-old)/old]*100= precent increase in diameter
new tire size:36"
old tire size: 31"
new-old= 5"
5/31)*100= 16.12%

now taking that percentage...
[(new-old)/old]*100=precent increase
since we dont have new we solve for that and get
new=[(%increase/100)*old]+old
new=[(16.12%/100)*4.30]+4.30
new = 4.99

and since there is no 4.99 ratio for the toyota's only 4.88 and 5.29 i figured the 4.88 is closer than 5.29...might be a little underpowered on the trails but thats what t-case low is for correct? I would be more worried that with the 5.29's i'll be screaming on the highway.

 

[ToyTec Lifts]

The FZJ80 axles stock gears are 4.10 and came with 31 inch tires

 

[Tapage]

which it's your OD gear ratio in the tranny that are you planning to run .?

Toyota isin't great making huge OD gearing in they trannys .. also which it's the sweet spot in your engine ( rpm range ) to run in HW . ?

 

[97kurt]

3.4 Auto with 4.88 gears and I have 33s. Around town its fine, but in the hills its a dog. I could not imagine running that setup with 36" tall tires unless I had a supercharger.

 

[yotarunner98]

The FZJ80 axles stock gears are 4.10 and came with 31 inch tires

yes, i was calculating off of my stock gears in my 4runner not the stock gears in the axle's

which it's your OD gear ratio in the tranny that are you planning to run .?
Toyota isin't great making huge OD gearing in they trannys .. also which it's the sweet spot in your engine ( rpm range ) to run in HW . ?

I'm not sure to be exact. my stock trans was a 98 limited trans a340f, the trans i just put in it is from a 97 t100 auto (not shift on the fly though) so i'm not sure exactly what the trans gearing is.

3.4 Auto with 4.88 gears and I have 33s. Around town its fine, but in the hills its a dog. I could not imagine running that setup with 36" tall tires unless I had a supercharger.

i ran 33's on my truck with 4:30's for 4 years and never had a problem what so ever. never bogged down or anything. i even towed a 4k lb trailer from southwestern VA to NJ without any issues and plenty of power for the hills. I've been runnin the 36's with the 4.30's for almost a year now and it is dogging on the hills and constantly downshifting.

Now going off my current ratio of the 4.30's with the 33's which i thought was fine to the 36's here's what i come up with
[(new-old)/old]*100= precent increase in diameter
new tire size:36"
old tire size: 33"
new-old= 3"
3/33)*100= 9.09%

now taking that percentage...
[(new-old)/old]*100=precent increase
since we dont have new we solve for that and get
new=[(%increase/100)*old]+old
new=[(9.09%/100)*4.30]+4.30
new = 4.69

so by this the 4.88 should be slightly lower gear ratio than what i deamed was fine. putting 4.10 into the calculation which is a common ratio for toyotas (and stock ratio for the fzj80 axles) the ratio to maintain between that and 31's vs 36's would be 4.76 so still slightly deeper gears.

 

[sovereign]

i maybe wrong here but i have heard that if u run 5.29 with 35s it spins the same revs at hwy speeds as the stock 5speed idk if this helps but just thought i would put that out there

The V6 Auto with 5.29s and 255/85r16 tires will be within 30 rpms of a V6 manual with stock 265/70r16 tires at all relevant highway speeds, per using the calculator here: Gear Ratio Calculator