What gears

[blairsj]

Hey Guys. Need some gear ratio suggestions. So just got some one tons 14ff rear and getting in a costom 14ff front passenger drop. Going to start building up the rear pulled it out of a 2000 Chevy 3500.
They will be going in a 1990 blazer with stock 350 tbi 700r4 and np241tcase. 35in tires with 4in lift. She will be a daily driver and will be going 70+ on highway. Was thinking might go up in tire size a few inches. Anybody have the same set up and what do they run? Thanks for all suggestions and any replies. Trying to get to stock numbers with the changes

 

[Strick]

4.10 or 4.56 will allow cruising in OD.

HS

 

[blairsj]

What would be better of the 2? I was thinking 4.56 but will it still be good if I upgrade tire to 38in

 

[PartsMan79]

I would go 4.88. That is a lot more tire weight and wind resistance than the stock tires.

 

[nvrenuf]

Having overdrive allows you to run more gear than the typical 3spd truck (of that era). Also having 35's now and wanting something bigger really means you need to be choosing a gear ratio for the future, not today (even if they are installed today). Gear swaps are expensive and require a certain level of expertise, so you don't want to do it twice.

Personally, I would look at 4.56 or 4.88 gears for tires in the 37"~38" range.

@PartsMan79 is dead on about the bigger tires and weight, they're fun but they add quite a load to a truck.

Something else to consider, 14 bolt front axles are BIG and hang low so with smaller tires (35's) that thing is going hit / drag on everything. If you THINK you might not go to a 38" tire you might consider a typical D60, this could save 2"+ of ground clearance at the diff.

 

[gmbellew]

with the OD trans, 4.56 minimum with 35s. i"d probably lean more toward 4.88.


check out-> http://www.grimmjeeper.com/gears.html

 

[bucket]

I would go 4.88. That is a lot more tire weight and wind resistance than the stock tires.

Yep! Exactly!

Keeping rpm/speed ratios similar to stock doesn't work with more rolling resistance and more wind resistance. Especially when trying to mimic the tall ratios GM did in the 80's.

 

[blairsj]

Thanks guys, as for ground clearance, I’m thinking about shaving the diff which will give me anywhere from an inch to 2 inches depending on how I shave it, but I’m looking into that and seeing if that’s a long-term reliable option. The website grim jeeper I know about that I’ve been on there looking at stuff and seeing what the speed and RPMs would be at, just wanna cover all my bases before I purchase gears so now I’m leaning more towards 4.88 might be a better option for when I do go 38 tires I might go right to 38 as soon as the axles get put in. Just want to really make sure, seeing as this will most likely be a pavement queen just good driving, but it’s always good to be able to go off the beaten path I do like to explore. but nothing too crazy not rock crawling or anything like that (for now lol) but I do like to camp.

 

[SquareRoot]

Shall we discuss mpg? Lol. Better buy stock in Shell.

 

[CalSgt]

Thanks guys, as for ground clearance, I’m thinking about shaving the diff which will give me anywhere from an inch to 2 inches depending on how I shave it, but I’m looking into that and seeing if that’s a long-term reliable option. The website grim jeeper I know about that I’ve been on there looking at stuff and seeing what the speed and RPMs would be at, just wanna cover all my bases before I purchase gears so now I’m leaning more towards 4.88 might be a better option for when I do go 38 tires I might go right to 38 as soon as the axles get put in. Just want to really make sure, seeing as this will most likely be a pavement queen just good driving, but it’s always good to be able to go off the beaten path I do like to explore. but nothing too crazy not rock crawling or anything like that (for now lol) but I do like to camp.

Its your money...

14 bolt for the front just to go camping on 35" tires is overkill. There are a ton of 6500 pound jeeps rock crawling on 37's with only D44's. Theres also a ton of the later model jeeps on 38's 39's and 40's that survive on pavement just fine, AKA Mall Crawlers

 

[Strick]

Jeepers want 4.88 gears with 33's. Jeepers aren't trucks, they don't do the work of a truck & they don't hold up like a truck...unless you build them that way. They are great on the trail after built.
I've usually had a 14FF out back & Dana60 up front & wheeling on 36-38 tires with 4.56 gears. Pulled many a Barbie Jeep from a jam or stuck. 12mpg with a 350/350 in my '76 LB & 16mpg on my CUCV. Neither were OD trans.
I'm with @CalSgt in saying a Dana60 or 14 front is overkill for a daily whip with 35's. I've broken spider gears & stripped axle shafts in GM 10 bolt fronts but have never had any issues with a Dana44, 44HD or 60. Even with 44's hung on them.
With that, I've just locked both 10 bolts & 4.56 geared them on my '87 V10; 6 inch lift with 35x12.50 15's.
Good luck with filtering out all of our opinions while also considering our experiences as well.

HS

 

[nvrenuf]

Shall we discuss mpg? Lol. Better buy stock in Shell.

It probably wouldn’t be unreasonable if the motor isn’t crazy.

My 454 w/ qjet gets about 10 mpg’s running 55-60 mph (5.86 gears and 40’s). It gets less with other carbs.

 

[Zelph]

Stock tbi, 35’s and 70+ on the freeway?
Are you near the Sierra Nevada Mountains? Big Bear?
That stock tbi with 35’s isn’t going to hold you at 70 mph as soon as you get a whiff at an incline.

 

[blairsj]

True on the incline, I live in the santa cruz mountains and when I get to incline i slow down to around 50. Mpg not worried about if I can keep in no lower then 10mpg ill be happy. Right now i get about 12mpg.
And yes for what I will most likely be doing with the truck 1tons are over kill but I want this thing bulletproof for when things do get dicey. Future plans are coil over suspension in the front and upgraded ORD custom leaf springs in the back possibly even coil overs in the rear four link suspension. And an erod ls under hood as i live in cali, but that way later to many hoops to jump through right now. For now just have to dial in the gear ratio so 4.56-4.88 with 35-38 tires. Can’t go much higher on lift or I’m a need a stepstool to open up the back (roll down window reach in to open) seeing as I’m only 5.5