What else do I need to look at and think about for trail rig?

[jwatt38]

I've started my build thread on here, but I wasn't sure where to post a generic all-encompassing question. My goal is to build my suburban into a capable trail rig, that I sleep in the back of. I think I have my lift sorted, tire size picked out, recovery systems/ideas are sort of hashed out, exterior lighting, etc. Honestly, that's all the easy crap for a "not a car guy" to pick out with minimal knowledge. Where I'm lost, where there seems to be so much "no this, no that, screw that swap it" is the drivetrain. From the engine to axles.

It's a '93 K1500 Suburban. All stock and lifted the redneck way, I will be fixing the lift.

When I got this beast I read that basically everyone hates the 350 TBI engines and is like "LS Swap it bro" or "diesel swap bro". I don't want to, nor does my bank account roll like that. I found one website where a guy lists out all the good places to spend money and the wastes on this engine, and I think he suggested swapping cams and that's about it internally. most everything else was just "put ACDelco parts on and it's fine"

I think I'm a smart dude but for some reason gears just do not compute for me. I cannot wrap my head around transmissions or differential gearing or any of that.

Goals. Capable but not insane crazy trail rig, Colorado pass type rig. Decent highway cruising speed and milage, if I can only have one I want fuel economy, I'm typically not in a rush to get nowhere anyhow. Planned tires will be 35" def no bigger than the crazy 36" tires on there now. Planned 4-6" suspension lift. I don't know what other info would be relevant. Most likely just me in the truck but the woman will join sometimes, rarely loaded with all 4 (kids are older and too cool for us now) of us unless some SHTF type craziness.

I don't necessarily need all the answers handed to me, I can read just fine lol. But maybe some good advice blogs or links to other posts addressing pieces of the problem. Just good trustworthy knowledge. Learning materials. I appreciate any and all help.

 

[mtl111]

I have a 99' lifted 2 door Tahoe so someone else will have to chime in on what mods for the TBI 350. My experience with the best place to spend money is in some lower gears. My tires, according to BF Goodrich specs are close to 34" and they are pretty heavy. I had been running the stock gears "3.42" for quite awhile and honestly it sucked. The truck would constantly downshift and upshift on even the slightest hills and pulling a trailer was a chore. I ended up putting 4.56 gears in it front and rear with a Detroit Truetrac in the rear and heavy duty axles from Nitro Gear.
It was like getting a new engine installed after that! Alot more power, she goes up whatever hill and rarely if ever downshifts. You may think these are way too low but I used some of the gear ratio calculators available online to figure what ratio i wanted to go with. Driving 60mph in OD , she is running about 1850rpm. My gas mileage actually went up after doing the swap.
Some may say to do a solid axle swap and I had thought about this as well but she goes everywhere I want and i have no intention on running anything larger than a 35 so I didnt see the need for the HUGE cost of doing a swap. If you plan on running larger than a 35 and are going to be doing some rock crawling rough stuff, then yes you need a 14 bolt in the rear and a Dana 60 up front because you'll eventually destroy the 10 bolt rear and the front diff.
Keep that TBI tuned up good, throw some lower gears in it and you'll be happy.

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[Hipster]

My Tbi seems to do just fine with some mild off road trail riding in stock trim. Off roading you have 4-lo available so there's that for torque multiplication. I have 33's and 3.73's and it does ok on the highway. It's borderline really.. 35's are most definitely going to call for a re-gear. Agreeed with MT above, running along under geared lugging along with constant gear changing is no good for the trans and it's not beneficial to mpg's either. You get better mpg's when your running down the highway when the rpm's are farther into the torque curve.

If you like to get into water I would extend all vents to a higher level, and if equipped with a Gov-Loc replacing it might be a consideration.

You'll benefit more from the gear swap then trying to find a little more from the engine.

 

[stutaeng]

I have a 99' lifted 2 door Tahoe so someone else will have to chime in on what mods for the TBI 350. My experience with the best place to spend money is in some lower gears. My tires, according to BF Goodrich specs are close to 34" and they are pretty heavy. I had been running the stock gears "3.42" for quite awhile and honestly it sucked. The truck would constantly downshift and upshift on even the slightest hills and pulling a trailer was a chore. I ended up putting 4.56 gears in it front and rear with a Detroit Truetrac in the rear and heavy duty axles from Nitro Gear.
It was like getting a new engine installed after that! Alot more power, she goes up whatever hill and rarely if ever downshifts. You may think these are way too low but I used some of the gear ratio calculators available online to figure what ratio i wanted to go with. Driving 60mph in OD , she is running about 1850rpm. My gas mileage actually went up after doing the swap.
Some may say to do a solid axle swap and I had thought about this as well but she goes everywhere I want and i have no intention on running anything larger than a 35 so I didnt see the need for the HUGE cost of doing a swap. If you plan on running larger than a 35 and are going to be doing some rock crawling rough stuff, then yes you need a 14 bolt in the rear and a Dana 60 up front because you'll eventually destroy the 10 bolt rear and the front diff.
Keep that TBI tuned up good, throw some lower gears in it and you'll be happy.

Sent from my SAMSUNG-SM-G930A using Tapatalk

Basically, this sums it up.

Engine mods is a different question altogether.

But why do you say that you can't wrap your head on gearing? When you change to a larger tire, you are basically changing the final gear ratio. Think of it like changing to a smaller sprocket on the rear wheel of a mountain bicycle. Your acceleration will be worse after going to a larger tire. Pretty easy to grasp the idea physically, I think.

What re-gearing your differential does is restore your original final gear ratio, but you can go higher or lower, depending on what gears you put in. There's calculators where you input transmission OD ratio, axle ratio, and tire size, speed, and it will give you RPM. You can play around with any of those parameter. Ideally, you want to be near the engine peak power range.

I helped my brother swap his 10 bolt in his '90 C1500 RCSB a few weeks ago. He found a 6 lug 14 bolt from a 2500LD with 3.73/G80. His original axle ratio was 3.08 and an open differential. He's running later model rims and tires. Nothing huge. He said he liked the swap overall. Less than $400 in all. He was thinking of re-gearing his 10 bolt, but the swap was obviously the way to go: stronger axle, better gearing, larger rear brakes and a G80 locker. All for about the same as regearing his 10 bolt if he paid someone to do it.

BTW, a rear locker would be a must if you don't have one already!

 

[skylark]

I agree with the above. Don't fear the gear! I personally would go 4.88 gears with a 9.5 14 bolt and a locker. As mentioned above the 14 bolt is stronger and comes with larger brakes which would be a help stopping the mass from larger tires. I would definitely recommend the 1 ton caliper swap and consider hydroboost. You need the biggest tranny cooler that you can fit behind the grill. I would also do a deep tranny pan. If you don't already have a radiator with the 34" core then I'd swap to one. I would bypass the factory in the radiator tranny cooler/heater. As for the engine they are dang near bullet proof. The best thing that you can do is ditch every single piece of the exhaust from the manifolds to the tailpipe. Rebuild the throttle body with a fuel pressure bump to 15-18 pounds and run a AC EP381 fuel pump to ensure good fuel supply. If you want to swap a cam then great, the stock one sucks, unfortunately the heads suck too but they are well matched to the cam because they are such a low flowing head. If you start down the rabbit hole of a cam you might as well plan on Vortec heads, Vortec style intake, tbi adapter and burning ECM chips. Either someone can do it for you with various results or you can learn how.

 

[ccreddell]

I would add that the 8.2 front diff is like glass when you start running anything bigger than a 33 in tough off road conditions. On the street you can get by with it, but with that heavy of vehicle, and semi-tough off road situations it gets iffy. I have a 99 2dr Tahoe that Im swapping the 14boltFF and 9.2 front diff out of a 99 2500 suburban. Actually, Im shortening the whole frame and putting it under the Tahoe. It helps that it already has a 4" lift.

 

[stutaeng]

I would add that the 8.2 front diff is like glass when you start running anything bigger than a 33 in tough off road conditions. On the street you can get by with it, but with that heavy of vehicle, and semi-tough off road situations it gets iffy. I have a 99 2dr Tahoe that Im swapping the 14boltFF and 9.2 front diff out of a 99 2500 suburban. Actually, Im shortening the whole frame and putting it under the Tahoe. It helps that it already has a 4" lift.

What? Now that I would like to see a build thread about! A 2500 Tahoe? LOL

That's the 9.25" front, right?

 

[ccreddell]

Yes sir.

 

[skylark]

What? Now that I would like to see a build thread about! A 2500 Tahoe? LOL

That's the 9.25" front, right?

Me too!

 

[351FUN]

I have a 99' lifted 2 door Tahoe so someone else will have to chime in on what mods for the TBI 350. My experience with the best place to spend money is in some lower gears. My tires, according to BF Goodrich specs are close to 34" and they are pretty heavy. I had been running the stock gears "3.42" for quite awhile and honestly it sucked. The truck would constantly downshift and upshift on even the slightest hills and pulling a trailer was a chore. I ended up putting 4.56 gears in it front and rear with a Detroit Truetrac in the rear and heavy duty axles from Nitro Gear.
It was like getting a new engine installed after that! Alot more power, she goes up whatever hill and rarely if ever downshifts. You may think these are way too low but I used some of the gear ratio calculators available online to figure what ratio i wanted to go with. Driving 60mph in OD , she is running about 1850rpm. My gas mileage actually went up after doing the swap.
Some may say to do a solid axle swap and I had thought about this as well but she goes everywhere I want and i have no intention on running anything larger than a 35 so I didnt see the need for the HUGE cost of doing a swap. If you plan on running larger than a 35 and are going to be doing some rock crawling rough stuff, then yes you need a 14 bolt in the rear and a Dana 60 up front because you'll eventually destroy the 10 bolt rear and the front diff.
Keep that TBI tuned up good, throw some lower gears in it and you'll be happy.

Sent from my SAMSUNG-SM-G930A using Tapatalk

Man, that's surprising. I was thinking 4.10 would be the way to go with my 33's but maybe not. 4.56 was what I was thinking for my F250 on 37's, but it also has no OD.