Best gears for 34 inch tires?

[Affronblaze84]

Hey guys,

I’m sure this question has been asked before but I couldn’t find any threads, so here I am.
I need to re gear the axles in my 1984 k5 blazer. My setup is a th350 with a 2200 to 2500 stall converter. It has the stock gear ratio( I haven’t checked but its either 2.73s or 3.08s) on 33 inch tires.
The truck is an complete dog with absolutely no power. It’s daily driven and sees a moderate amount of time off road and in the mud.
It needs new tires soon and I’m planning on putting the tsl 34 inch super swampers on it. What would be the best gear ratio for a th350 with a stall and 33/ 34 inch tires? I was leaning more towards 4.10s but I wanted to ask the professionals here first lol

Thanks!!

 

[ktmoutfront]

How freeway time will it see?

 

[nvrenuf]

Check an online gear calculator and make sure your choice results on a cruising rpm that’s higher than your stall. Running under the stall rating constantly creates a lot of heat in the trans.

 

[Wes Harden]

4.10's with 34's is do able @ 2700 rpm at 65 with 33.5" tires, 4.33 would be 2822 same size tire. 4.56 would have you right at 3k rpm. Gm made these trucks with 4.10 gearing, th350 and 31" so is do able

 

[Bent77]

Yep, 4.88s barely get you off the converter at 55

what ups with the high stall?

 

[Bent77]

 

[USSkoval]

What does the converter foot brake stall at? The average stock or mild small block will tend to be at the very bottom of the listed stall range. Imho, a 4:10 will probably be a good all-around.

 

[Affronblaze84]

Yep, 4.88s barely get you off the converter at 55

what ups with the high stall?

When I bought the tranny it already had the stall on it. I figured what the heck it’ll give me more launch when in the mud, so i kept it on. I’m beginning to see it may not have been the wisest choice for a daily…

 

[Affronblaze84]

How freeway time will it see?

Maybe once or twice a week? Not rlly an everyday thing

 

[Affronblaze84]

Check an online gear calculator and make sure your choice results on a cruising rpm that’s higher than your stall. Running under the stall rating constantly creates a lot of heat in the trans.

I kind of figured it’d cause more heat, so I hooked up the biggest cooler I could find and bypassed the stock radiator. Could the trans potentially blow up from running under the rated stall rpm?? Or would it just run hot

 

[SPLATT]

4:10 min to 4:56 max. Somewhere in the middle would be more ideal, at least to me.

 

[paratrooper307]

4:10 min to 4:56 max. Somewhere in the middle would be more ideal, at least to me.

A 4:30 would be nice, but I don't think anyone makes one. Usually you see 4:56 being the next step. If it's a true 34, the 4:56 might be the way to go because the urge to step up to larger tires often comes.

 

[SPLATT]

A 4:30 would be nice, but I don't think anyone makes one. Usually you see 4:56 being the next step. If it's a true 34, the 4:56 might be the way to go because the urge to step up to larger tires often comes.

I actually found some 4.30 gears for a 8.5 on Summit Racing's website. I was a little surprised.

Pardon Our Interruption

 

[muddybuddy]

Could the trans potentially blow up from running under the rated stall rpm?? Or would it just run hot

Heat kills transmissions, so unless you want to risk rebuilding the trans after it gets toasted, I wouldnt let it get hot

 

[paratrooper307]

I actually found some 4.30 gears for a 8.5 on Summit Racing's website. I was a little surprised.

Pardon Our Interruption

Cool. I learned something today. I think I'd still go with the 4:56-better power and the option to step up to a bigger tire.

 

[Blue85]

I doubt in use you could tell any difference between 4.30 and 4.56. However, if you ever swap axles, you may not be able to get 4.30 for the new one.