3.08 gears with 35" tires?

[1985K10]

Like the title says, I have a 1985 Chevy K10 with 35" tires and 3.08 gears. The truck is powered by a 305 V8 with a 4 speed automatic transmission. I was curious if the 3.08 gears would be a good set up for the 35s. I want to use it as a daily driver, to get back and forth to work. I DO NOT plan on using the truck for off roading, just a cruiser. I would love to change the gears in it but due to a broken bolt in the rear end, it's kind of impossible. I found 3/4 axles and was thinking about switching them out but I would HATE to have to buy new tires and wheels again, considering I have 15s right now. Thanks for the help.

 

[crazy4offroad]

3.73 or 4.11 would be a better selection, especially if you have an early 700R4 in there. Relieving the stress on the trans will increase its lifespan 10x.

 

[GreaseDog]

3.73 or 4.10 gears would be a good selection if you did NOT have a 700r4. 4.56 its about where you want to be with a 700 and 35s

 

[skysurfer]

Well now I'm curious about which bolt can make it impossible to change the diff gears. You have a pic?

 

[nvrenuf]

Well now I'm curious about which bolt can make it impossible to change the diff gears. You have a pic?

Probably the retaining bolt for the diffs center pin. It's common and would prevent you from easily removing the axle c clips etc. it can still be removed but not without a fair amount of work.

While the 4.10's or 4.56's would be best anything is better than the current 3.08's.

 

[Swims350]

agreed we had an 86 with 3.08's and 33's and gas sucked around town with a 305 it was gutless but with a fresh 350 it wasn't bad, not good mileage at all though.

I'd do 4.10's minimum.

 

[1985K10]

Yes, I have a picture. I even drew a red circle around the broken bolt to help identify the location. Half of it came out, the other half stayed inside. I'm not sure how I can remove it without doing alot of work, as there isn't much room to work in. I know where I can get another set of half ton axles if needed.. I would much rather go 3/4 ton but like I said earlier, I don't want to have to buy new tires & wheels. I already have 35" swamper tsl sx and 15" Mickey Thompson classic locks. I would rather just swap gears in the existing axles and call it a day.

You must be registered for see images attach

 

[johnmc]

thats the bolt i was thinking it was. not fun. we have 35's but with a set of 4.10's we love it around town. we dont have overdrive . You will heat up the trans with 3.08 gears with a lot of stopping and going. add a cooler. rember what you change in the rear you have to do in the front. if i was you i would just look for a donor truck with the right gearing and swap axles. there is a guy up here has a set of 4.10's for 400.00

 

[nvrenuf]

Yeah, that's the center pin retaining bolt.

The "easiest" way to get it out now will be to get a BFH, a big punch and start beating it to death. The remaining part of that bolt looks like a 1.5" long pin that goes through the center pin and into the carrier itself. The goal is to hit the center pin hard enough to shear the retaining bolt so it will come out.

 

[HotRodPC]

WOW !!! 3.08's, 35in tire, and a 700r4??? That trans is doomed in short order. You need a gear change. Looks like good advice above already. If you're keeping the 700r4, and doing a gear change, I'd go with a 4.10 since you have the OD to compensate and maybe even a 4.56. That would be my choices if I was paying for a gear change. The other suggestion to get off cheap, is find you a used 12 bolt or 10 bolt from another truck. In C10/K10 1/2 ton models there are some 3.73's out there used that can be had fairly cheap, like a $100-$150 for drum to drum rear end. Even 3.73's will be a drastic improvement over those wussy wagon, station wagon 3.08's.

 

[1985K10]

I already found an '86 K5 blazer with a 350 tbi, 700R4 and half ton axles with 3.73 gears in it for $600 or best offer. I guess I'm going to stick with half ton axles, that way I can still use my 15s.

 

[HotRodPC]

$600??? That thing must be a major POS. If not, I'd be all over that and it be in my driveway. That's a steal for a K5 around here. You can get a 4x4 Burb in rough shape for that, but not a K5.

 

[bucket]

You won't even like the 3.73's with 35's. It won't be too bad though if you never use OD.

 

[oneluckypops]

3.73 or 4.10 gears would be a good selection if you did NOT have a 700r4. 4.56 its about where you want to be with a 700 and 35s

This is the correct answare

IMHO I would Reccomend 4.56's for your application wheeling or not your transmission is stressed big time. Heres what I usually reccomend for tire size versus ratio with an automatic transmission w/overdrive on a daily driver.
I would also suggest using a bigger Transmission cooler aswell as the radiator. An 18,000-24,000 gvw cooler is what i like to use. They will prolong the life of your transmission greatly and worth the extra time and money.

stock tires thru 31" = 3.73's
32" thru 33" = 4.10's
34" thru 35" = 4.56's
36" thru 37" = 4.88's
38" thru 40" = 5.08's

 

[1985K10]

Well, that's another thing. I can't get my transmission to shift into overdrive, even if I manually shift it. Therefore it's like I already have a 3 speed transmission. What gear ratio would a 1990 1/2 Suburban have? I found a nice 4x4 that I could buy as a donor truck and use the axles off of it.