700r and 37" tires what diff gears to use ? (1 Viewer)

[james70toy]

Hi i'm building an fj40 with a sbc 350 ,700r and plan on running 37" or 38" tires. I just bought some axles with 4:56 gears. Would these work ok or do i need to regear them? Thanks

 

[bustanutley]

Simple calculation

(Stock tire size)/(stock gearing) = (new tire size)/(new gearing)

New gearing = X

Solve for X

 

[james70toy]

Would that be the same calculation to use for an automatic with overdrive and a stick? Im building a daily driver / wheeler.

 

[bustanutley]

to maintain stock rpm ranges on the street, yes. To figure out what rpm vs. speed for gearing is another simple calculation. To answer your original question, 4.56s will not be deep enough with 37-38s to make overdrive useful, especially with an auto.

 

['74 UA FJ]

With a 350 and 38s, I would go with a 400 trans if you plan on beating on it any. You probably won't be daily driving it for very long with 38 inch tires.

 

['74 UA FJ]

Hi i'm building an fj40 with a sbc 350 ,700r and plan on running 37" or 38" tires. I just bought some axles with 4:56 gears. Would these work ok or do i need to regear them? Thanks

What are you doing for a transfer case(s)?

 

[PPFJ60]

I am running a 350 stroker / 700R4 with 4:88 gears and 37" tires. Plenty of go on the high end but I wanted lower gears so I put in a NP203 gear splitter between the 700R4 and the Toyota split transfer case. Now I have lots of high end and about 60:1 in double low.

So I would think 4:56 gears would be too high for 37"or 38" tires.

 

[james70toy]

I have a dana 300 t case. I'll be running 37", nothing to crazy just want a streetable wheeler that i could drive to the trails. So
maybe 5:29?

 

[Tapage]

I have a dana 300 t case. I'll be running 37", nothing to crazy just want a streetable wheeler that i could drive to the trails. So
maybe 5:29?

I'm not a lover of the 5.29 in Toy axles .. ( are they ? ) 4.88 would be my lowest and always you have the 4.:1 option in the D300 ( that's my favorite non yota t-case )

 

[james70toy]

Ya they are toyota axles 76 fj 40. Front disk , arb's front and rear with 4:56 gears.

 

[pule]

I drive a sbc350+Th400 and 4.88 on 38´s in my cruiser and it feels good for DD and weekend warrior.

 

[Cruisertime]

Hi i'm building an fj40 with a sbc 350 ,700r and plan on running 37" or 38" tires. I just bought some axles with 4:56 gears. Would these work ok or do i need to regear them? Thanks

Read my sig. I drive my '78('74 really, DMV has told me to register as '78 due to tub) daily, built 700R4 and 38's. Stuffed with 5.29's and have no issues. My tranny is mild built to handle 500lb ft/tq. And thanks to DrDobro, I have a non-us full float rear with polyperf shafts. I avg about 27 miles round trip, anywhere from 85mph to bumper to bumper. No issues.

 

[fj40charles]

I have a dana 300 t case. I'll be running 37", nothing to crazy just want a streetable wheeler that i could drive to the trails. So
maybe 5:29?

700R4 1st gear x Dana 300 x ring/pinion

3.05 x 2.6 x 4.56 = 36.16 x 2 (torque converter) = 72:1 crawl ratio.

I say that is plenty with some 37" tires.

For reference, I used to run a TH400, 3 speed LC tcase, 4.88 r/p. 2.48 x 2.3 x 4.88 = 27.8 before torque converter multiplication. This worked out well for me when I was running 36" tires.

Personally, I don't think you need the 5.29 gears. 4.56 ring/pinion will be just fine for wheeling and street driving.

Also, need to keep in mind the torque converter will provide at least 2x multiplication.

 

[james70toy]

Thanks for the info guys, it good to hear real world driving experience.

 

[xjnation]

I've got a 4.3/4L60E combo pushing 35s w/ 4.10s and have no problems at all. The 4.56s should work well, especially behind a v8.