I am looking at buying some 36x12.5 TSL's and am wondering if they are too much for my motor and gears. I have a 300hp 350 with 3.73 gears. Will this be a problem (break something) or will it hurt anything? I am pretty new to this and appreciate all the help.

With 36 inch tires, you will need a 4.56 or 4.88 gear set. Your current gears will bog you down with tires that big.

I ran 35s and 4.11 with a "small" 5.0L TBI engine with no problem... just right on road but a little tall offroad... that was with a SM465.

it'll work though... what axles do you have?...

Seriously, 36"s aren't so big that you are going to kill your motor by running 3:73s. It is going to kill your low end somewhat, but unless you are using this rig only for hardcore rockcrawling and the like, I wouldn't run anything more than 4.56s.
I run a stock 454 with 4.11 gears and 38.5"ers and it does suffer a little low, but not drastically.
Just my own opinion.:)

A buddy of mine runs 36s whith 3.73 whith a shitty 350. You can do it but i would be looking into an upgrade.

Its not that bad. Actually would be pretty good for just running mud and trails. Not so good for rocks.

what tranny do you have? if its a none over drive you will be fine, if its a 700r4 I hope its in good shape and I would shift out of overdrive on long hills

Like has been said, will be fine around town/trails/mud but not great in the rocks.

I'm running a tired AMC 304, 4.10 gears and 38.5.16 TSLs. The gear to tire size ratio, almost puts me back at the stock spedo gears (and I have no idea what this).

For having fun in Indiana, I'm in good shape with this setup and don't plan to change it out.

I had the same setup and it worked. Youll notice some power loss in the low end department but it should still work. I had 1/2 as much power as you do but i had lockrites front and rear on 1/2 tonners. I recommened an upgrade as i could'nt stand the shitty gear ratios. btw, my tranny took a dump when i had 3.08's and the same tires and it was a th350 so you might be okay as i thought 3.73's were an upgrade but now with 4.10's i have no problems whatsoever.
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I think you should be fine. I have a 350 HP sbc and 3.08's with 35" tires. I am happy with mine. It might not be great for rocks, but it does great on the road and in some mud. I think with 3.73's you should do just fine.

Tom

I'm running 5.13's, 38's and a 4 banger that makes what, 120hp?, and I get around fine. I really think you'll be ok.

i have a 400 hp 355 with 36 tsl's didnt break anything yet!!!!!!