3.08's with 33's or 35's?

[keanevann]

I already have done all the math and all. I just want to know first hand. My wife is building a daily driver and it has 3.08's. Does anyone have these gears with 33's or 35's? How do you like them are they good for driving? I wont be off-road. Thanks.

[bouncytruck]

I'm running tires that are approx 31.5" tall and the gearing is just about right. I can't burn the tires, but it is a bone stock truck.

My last Blazer had 4.10's with 35's. That seemed like the correct gearing. My first Blazer had 3.73's with 35's and it was under geared.

[Firebirdjones]

My 72 blazer has factory 3.07 gears and I run 33" tires on it.

With the original 355/350 turbo it would cruise 70 mph at 2400 rpm and get 16 mpg. It was nice for long cruising, but it was a bit sluggish on take off, till about 20 mph. Nothing horrible though, I daily drove it like that for years. I would have personally liked a 3.73 gear with this combo if I had stayed with the 350 turbo trans. I'd rather have a bit more take off and sacrafice some cruising rpm,,,,,However...

I have since switched to a 6.0 vortec with a 4L60E behind it. With the 3.06 first gear and 1.62 second gear, it has more effective gear ratio now and moves out nicely from the stop lights. With the overdrive it cruises at 1400-1600 rpm at 75 mph and now gets 22 mpg
It's just about perfect, and towing in 3rd gear still gives me a decent cruise rpm like the 350 turbo originally had.
In the end though, I have everything here to swap it all over to 3.73 gears, and I'm back and forth about it. I'd like even more get-up-and-go, it's never enough

[AJs72K5]

You're engine will be dogging it with 3.08's and a tire that large. Transmission will be downshifting constantly too.... assuming you ever make it out of 1st gear.

[Firebirdjones]

Originally Posted by AJs72K5

You're engine will be dogging it with 3.08's and a tire that large. Transmission will be downshifting constantly too.... assuming you ever make it out of 1st gear.

Naa, I never had the problem with mine. Like I said, cruised nice down the highway, and even the little 355/350 turbo combo would move it around town fine.
What I did was adjust the governor along with an adjustable vacuum modulator to stretch out the shift points at part throttle just a tad. It helped get the truck moving, and still got 13 mpg around town.

[old man jimmy]

with the price of gas what it is today. I'd stay with the 3:07's. Mine started life with 3:07's, but when they dropped the speed limit to 55, it was always bogged on the hills in 4th gear, so went to 3:73. More rpms means more gas. and it don't sound like you'll be pulling a trailer or off roading. for just crusing around I'd leave it alone. put the money you'd spend on two sets of ring and pinions to better use.

[Firebirdjones]

Originally Posted by old man jimmy

with the price of gas what it is today. I'd stay with the 3:07's. Mine started life with 3:07's, but when they dropped the speed limit to 55, it was always bogged on the hills in 4th gear, so went to 3:73. More rpms means more gas. and it don't sound like you'll be pulling a trailer or off roading. for just crusing around I'd leave it alone. put the money you'd spend on two sets of ring and pinions to better use.

I switched my drivetrain to a 2004 6.0 LS (vortec) with a 4L60E behind it. I still have the 3.07's in the truck, and it's really a pleasure to drive.
I'm not having issues with bogging on the hills (Prescott AZ is mountain terrain) even at 55 mph cruising around it might unlock the converter to maintain speed but that's the extent of it. At highway speedlimits (75 mph) it stays locked and cruises effortlessly getting 22 mpg. The grunt of that 6.0 is letting me get away with less gear and low cruising rpms without much fussing at all. The original 350 would be complaining for sure.

I do offroad our blazer in the mountains as well as tow a utility trailer and a camper. It does fine off road, low range has more grunt than I need with the transmissions 3.06 first gear. Climbs any rocky grade I care to try.
Towing the camper works nicely as well, I tow in 3rd gear and with the 3.07's it cruises at 70 mph at about 2200 rpm (with converter locked). Seems to be a sweet spot for the 6.0 vortec, it pulls the hills easily.

Without the 6.0 vortec in there, I'd probably be more inclined to install those 3.73's. I still may do that when things slow down a bit. I can't help but remember how good the 4.10 gears worked in a similar setup I had years back I like the 0-60 power with a little stop light fun mixed in.

[NW_Ryker]

With a tired 350/350 combo, 3.07's, and the 31's, my truck is really slow to get up to speed. On top of that, I don't even get decent gas mileage.

[1971k567cam]

Weird I am not getting good fuel economy eitherI am running 4.10 gear ratio 35s with a 383 and 700r4 has perfect power and drives great just does not get the best fuel economy just figured it was the nature of the beast. Oh ya and before the upgrade to 4.10 gears was running 3.07 and 33s was a dog and took a mile or so to get up to speed may have been worn out engine or old turbo 350 but was not a fan.

[old man jimmy]

these trucks are like driving a shoebox. not the best aerodynamics.. can't expect much gas mileage. but when I had the 3:07's, mines a 4 speed, and the motor was cammed, and a few other tweaks. Had plenty of get up and go. But not until it got to 2500 rpm's. May be different with the auto. All I had to do was run my gears further. I got about 15 mpg with 3:07's and dropped to about 11 with 3:73's. That's with 33 in. tires.

[mustardjimmy71]

what trans are you running?

when it comes to changing gear ratios i save that for last. You may decide to go to an overdrive trans witch has a lower 1st gear than a 3 speed. that will get you off the line a bit better and lower highway rpms

If your diffs are good and allready assembled i would use the money for the gear swap towards a 4 gear auto.

I have yet to hear of anyone who regretted swapping from a 3 to 4 gear.

[Firebirdjones]

Mileage isn't that bad, I find mine to be more than acceptable.

Running the 6.0 LS with a 4L60E, 3.07 gears and 33" tires. I'm getting 17+ mpg around town and 22 mpg highway. That's after custom tuning with the laptop. With stock tune I was getting 15/19.
It's better than most new SUV's out there.

I may give up a slight amount when I switch to a 3.73 gear.

[1971k567cam]

Thats next for me some lap top tweeking with 4.10 and 33s the best i got on freeway was 12 mpg. Now has 35s and got speedo calibrated again. I would love to see 20mpg highway and 15mpg city. Its a 383 with stealth ram fi running a ramjet ecm and wiring lt4 hot cam bbk twin 58mm tb all the parts work well together just rough on fuel. I run pretty much the same setup in my 89 2wd and it gets much better fuel economy and runs 13s in the quarter mile go figure.

[D.PASSMORE]

Originally Posted by bouncytruck

My last Blazer had 4.10's with 35's. That seemed like the correct gearing. My first Blazer had 3.73's with 35's and it was under geared.

I agree... Correct gears for tires. Better MPG with 3.08's and stock type tires...

I run 3.73 with 33's. Fairly stock 350/STD SM465, 12/15 MPG highway.

[Firebirdjones]

My old setup with a 355/350 turbo, still with 3.07 gears and 33" tires got me 13 mpg around town and a best of 16 mpg highway.

I don't guess that's what you guys consider correct gearing, but the mpg was respectable and it ran fine for years like that. It wouldn't win the stop light drags but it drove nicely

[Firebirdjones]

Originally Posted by 1971k567cam

Thats next for me some lap top tweeking with 4.10 and 33s the best i got on freeway was 12 mpg. Now has 35s and got speedo calibrated again. I would love to see 20mpg highway and 15mpg city. Its a 383 with stealth ram fi running a ramjet ecm and wiring lt4 hot cam bbk twin 58mm tb all the parts work well together just rough on fuel. I run pretty much the same setup in my 89 2wd and it gets much better fuel economy and runs 13s in the quarter mile go figure.

That stealth ram should be a sweet setup. I'm not sure how detailed the ramjet ecm lets you get involved with the tuning but you should be able to find some mpg in there.

[1971k567cam]

Still new at it but my budy and I bought mefi burn for it just have to get a wide band o2 on it and see where its to fat.

[Firebirdjones]

Sounds good. A wideband is a must have for tuning with any accuracy. I've used my Innovative Wideband for years on all the cars, carb and fuel injection. Hooks up to my laptop as well for tuning the computer controlled stuff. I don't know what I'd do without it.

[red71cheyenne]

Somebody refresh my memory. Will 3.08's fit in a 3.73 carrier? Seems like I remember they won't. I'd like to give this a try on both of my trucks, one for gas mileage and one just for driveability.

[Firebirdjones]

Originally Posted by red71cheyenne

Somebody refresh my memory. Will 3.08's fit in a 3.73 carrier? Seems like I remember they won't. I'd like to give this a try on both of my trucks, one for gas mileage and one just for driveability.

If you are talking about the truck 12 bolts, the carrier breaks into 3 gear ratio sections like this....
2.54-2.73/2.76-3.42/3.73-4.10

On the front Dana 44 the carrier gear ratios break like this...3.73 or taller,,,,and 3.92 and lower...

So in a nutshell you can switch 3.08's and 3.73's in the Dana no problem. But on the truck 12 bolt it requires a carrier change or a thicker gear/thinner gear depending on which way you go.

[red71cheyenne]

Originally Posted by Firebirdjones

If you are talking about the truck 12 bolts, the carrier breaks into 3 gear ratio sections like this....
2.54-2.73/2.76-3.42/3.73-4.10

On the front Dana 44 the carrier gear ratios break like this...3.73 or taller,,,,and 3.92 and lower...

So in a nutshell you can switch 3.08's and 3.73's in the Dana no problem. But on the truck 12 bolt it requires a carrier change or a thicker gear/thinner gear depending on which way you go.

Thanks for the breakdown. Didn't know you could get a thinner/thicker gear set that would make up for the differences.

[Firebirdjones]

Originally Posted by red71cheyenne

Thanks for the breakdown. Didn't know you could get a thinner/thicker gear set that would make up for the differences.

You can for the passenger car 12 bolts, I set quite a few of those up for people. I rarely get a truck 12 bolt in here, but I'm betting since it's available for the passenger cars then it's out there for the trucks.

I could check on it.

On the passenger rears, Richmond makes a thinner 3.73 for the 4 series carrier, and they also make a thicker 4.10 to install on a 3 series carrier. I believe it also goes a bit further, to 3.42 and 4.56.

When I bought the 3.73's for my blazer, I also bought a new 3 series Eaton clutch style posi, because the original rear was an open 3.07. I wanted to upgrade to the posi so I just bought the correct setup. I didn't bother to check for a thicker gear. But I'll check on it to make sure.

[Firebirdjones]

I checked Randy's Ring and Pinion with who'm I've dealt with many times. He stocks a Yukon brand (which is good quality).

He does infact have thicker truck 12 bolt 3.73 gears to fit the 3.42 and down carriers as well as thicker 4.11 gears that do the same thing. So no need to change the carrier if you don't want to. Hope that helps

[red71cheyenne]

It does, and I was looking on evilbay as well and there were a couple that said they would fit the 3.73 and up carrier as well. I'll just have to be careful which set I buy. I want to try it in my 71 to see if it will help my gas mileage. And in the Blazer as well since it is so slow! Thanks for the help.