4.88 or 5.29 (5 Viewers)

[MiSFiTiSM]

I looked around the forum and have been reading up on this a bunch but I haven’t seen anything exactly what I am running so I am making a post looking for ideas and suggestion from you fine folks.

I got a 1967 FJ40 with the stock 1F engine. Has both front and rear axle from 1985 FJ60. SOA conversion with Stock FJ40 front spring and stock 1985 FJ60 rear spring. Running 35x10.5x17 M/T’s. It’s 3 on the tree transmission.

It’s currently being built up from being completely stock 1967 FJ40 so I don’t have any drive time on it. It won’t be a daily driver but I will drive it around town a bit to show off but my main goal is to get into the mountains and desert with the family for camping and overlanding. Won’t be doing any crazy 4x4 but definitely climbing some hills and creek crossings. Not too worried about top speed but I want it to be reliable and safe and not be sluggish starting from stops. I’ll never have it on the freeway and plan on back roads to all my destinations.

Am I missing anything? 4.88 or 5.29.

Thanks in advance.

 

[Pighead]

4.88s should be plenty good with 35s. I got 4.88s in my Pig on 37s behind a 2F/F mash-up.

 

[pb4ugo]

You can find RPM calculators on the internet. I run 4:88's and 35" boggers, (Actual size is 33") it runs around 3000 rpm at 60mph. Your 3rd gear ratio is 1:1. You need to measure the actual diameter of your tires. You can figure your crawl ratio by 1st gear ratio X low range ratio X ring & pinion ratio. I run an SM420 1st gear is 7.05 X 2.46 low range X 4.88= 84.63:1 which is pretty low.

 

[EWheeler]

Get rid of that 3 speed before you spend money on gears.

 

[MiSFiTiSM]

Get rid of that 3 speed before you spend money on gears.

I was just thinking about that but I always loved my 3 on the tree haha

 

[EWheeler]

I was just thinking about that but I always loved my 3 on the tree haha

I too love the column shifter, but despise the 3 speed gear spread with the F engine in front of it, the gear splits on the 3 speed are terrible for a rig on 35's and stock gears. I have one, and I would replace the transmission before re-gearing the diffs. Best to do both if you can afford it! You can keep the column shifter with the 4 speed too.....

Post in thread 'tranny tech 403-thats 4 on the tree!'

Aug 2, 2022

Took longer than expected today due to family visiting, trips to Ace for some bolts, etc. But…..
Success!!!!!!! I’ll post more thoughts and details tomorrow when I have more time, but it drives fantastic with the 4 speed and the column shift is very easy to navigate (especially if you’re used to the 3 on the column already).
Here’s a video of the first real drive. It’s loud and hot with no trans cover but you can see everything working.

• Skreddy

• 
• 

 

[pb4ugo]

As @EWheeler said. Try to find gear reduction in the trans and Tcase. I did a lot of trail riding for a long time with stk 4.11's and then went to 4.88's. Because I had a lot of seat time w/4.11's, the minimal reduction was helpful but not enuff. Do the gearing math. You'll see the reduction from 4.11 to 4.88 is minimal and expensive. I eventually went to a SM420 and a tcase that offered overall all reductions that doesnt effect on road characteristics. I don't mind higher rpms at highway speeds because I run an SBC.

 

[EWheeler]

As @EWheeler said. Try to find gear reduction in the trans and Tcase. I did a lot of trail riding for a long time with stk 4.11's and then went to 4.88's. Because I had a lot of seat time w/4.11's, the minimal reduction was helpful but not enuff. Do the gearing math. You'll see the reduction from 4.11 to 4.88 is minimal and expensive. I eventually went to a SM420 and a tcase that offered overall all reductions that doesnt effect on road characteristics. I don't mind higher rpms at highway speeds because I run an SBC.

Along this thought line, find an early short cased FJ60 4spd and split transfer case. Do 3.3:1 low gears in the t-case and 10% underdrive in highgears in the splitcase. Utilize the parking brake on that rear FJ60 axle. Over time, look for a used set of 4.10's from an FJ62, or a couple of FJ80 rear diffs, those FJ60 axles you have likely have 3.73's in them? With 4.10 diff gears and the 10% underdrive in the t-case, its like having 4.56 gears in the diffs.

 

[1911]

You can find RPM calculators on the internet.

Here is my favorite. It has drop-down menus that include most Toyota transmissions and transfer cases, and you enter your diff ring gear ratio and tire size:

Gear Ratio Calculator - https://www.grimmjeeper.com/gears.html

If you do think about replacing the transmission instead of the diff gears, consider the H41. It's a non-USA market transmission that has a granny low (5.3:1) first gear that would pull 35's from a stop easily. Spector Off-road imports and sells them.

 

[bdog75]

If you can find a four speed bell housing and a four speed transmission you can get gears to mate your three speed transfer case. I ran that setup on 33's with the stock 4:10 and did fine. check out the gear ratio calculator (above) its great.

 

[charliemeyer007]

A 4sp tranny with the 3sp's transfer gets you a better low range low, still 1-1 in high range 4th.
You will need to change something on the front on the transfer input shaft.
Mark's off road has the part.

 

[Mark Jennings]

The stock 3 speed 1st gear is awfully tall for 33’s, 35’s…..and as stated above, the 4:88’s are a bit to close to the 4:11’s you had (have). I think k 5:29’s with the big tires would work if you are determined to keep the 3 on the tree and a stock F. I kept my 3 on the tree and 4:11 gears but run 31” tires….and they’re almost to tall for 1st gear.

Other than the PIA to pull the 3rd members, replacing gear sets is pretty economical compared to the labor and parts cost of transmission/T-case replacement. Your choice but IMO, I’d go with the 5:29s and install an Auburn posi in the rear.

 

[Ditcherman]

You can find RPM calculators on the internet. I run 4:88's and 35" boggers, (Actual size is 33") it runs around 3000 rpm at 60mph. Your 3rd gear ratio is 1:1. You need to measure the actual diameter of your tires. You can figure your crawl ratio by 1st gear ratio X low range ratio X ring & pinion ratio. I run an SM420 1st gear is 7.05 X 2.46 low range X 4.88= 84.63:1 which is pretty low.

I would just like to put a slightly finer point on the pencil and say that you don’t really care about the diameter of the tire, you care about the rolling radius at your pressure and weight on the tire. If the calculator happens to want diameter it is actual radius times 2, not the diameter of the tire.
Probably not a big deal just wanted to mention it in case it is.

 

[pb4ugo]

I think the rpm calculators take the tire circumference into account at a certain diameter. 5280' ÷ circumference = revolutions per mile.

 

[charliemeyer007]

Chalk mark on the center line where the tire and the pavement meet. Roll forward until the mark returns to the same position on the pavement. That's the closer to the actual tire circumference, then do the math for a better calculation of your actual low speed ratio.

 

[pbgbottle]

5:13’s don’t fit without some major grinding on the ring gear to slide the Center pin in. I too run the 4,11 and a sm465. With 37’s. Works good. I would swap tranny also before diff gesrs.

 

[bikersmurf]

I was just thinking about that but I always loved my 3 on the tree haha

Convert to 4 on the tree... Mark figured it out with the help of some other members.