Who's running 4.10's and 33's?

[norville]

Hey folks,

Listen I have a 77 3/4 sub. I'm looking at options. Now, I have 4.10's in it and I know these thing's came with 30" tires with those gears but the speed limit was 55 then. This will be a DD 12miles to and from work and 2x a week the interstate @ 70 for 30 miles round trip.

I keep telling myself that I need 35's to get into an OK rpm range.(2600) But I'd like to do 33' w no lift. They are plentiful and have more options in my price range new and used. Will I be dieing over the rpms? I have a 400 backed by a th350 and a 203(soon to be PT). I'd really like to stay in the double digits for mpg's

So, Who's running 33's and 4.10 how life for you? Is it a DD or just a trail; rig. Will I be sorry with these? I know bigger is better.

thanks for any input.

 

[tin man]

I had that combo in my 85 blazer for a while. It did O.k. I guess. I think that at 70 you might be a bit high in r.p.m.'s. You will have plenty of low end power though.

 

[Kyle Strong]

I run them, and it's not a dd yet, but will be soon. I have a 350/th350 with 33's and I run a little above 3000 at 70. I like them. Moves real well at low rpm. I don't know what I get for mileage, but I'm guessing low double digits, around 12-14.

 

[josh86k10]

I used to run 4.10's with 32's and loved it, but I had a 700r4 at the time. Low-end was awesome, at least for a tired 305. Without overdrive it'll be turning a little fast on interstate, but I don't think it'll be that bad. I used to run 80+ in my 71 C20 w/o overdrive and whatever gears were in the eaton rear (pretty low whatever they were) and it was tolerable.

 

[mdm365]

I have a77 blazer with 4.10's and a sm-465 at 70-75 im turning about 3000 rpm with 33's.I went to denver in it went down the road ok but it made me pay at the pump.I figure I was getting about 9-10 miles to a gallon. mike

 

[u2slow]

I've had 4.10/33s in my 6.2/th400 Burb and 350/sm465 Crew. I didn't like (and couldn't afford )to drive either one on the highway (3000rpm).

 

[steve_kibbe]

I ran 33 with 4.10's on my 83 k2500. It has a 6.2 diesel/sm465, I'm not sure about rpm's, but I could do about 85 mph max, sounded like hell with duals and glasspacks You should see peoples faces when you pass them

I averaged 17mpg

 

[lifted76k5]

My old truck had 4.56 gears and 33in tires. highway sucked (i avoided it at all costs), but on mountain roads and around town i loved it. (real fun to smoke riceburners in an old ugly truck) i only got 8 mpg. My dad is running 4.56 gears and 33in tires on his suburban. it has overdrive so the highway is fine. around town it gets around 15mpg, highway is closer to 10mpg. you should be fine with 4.10 gearing.

 

[redbeast77]

I'm running a '77 K5 350 / th350 / NP 203 - I'm currently running the factory 3.08 gears and I'm seriously considering the 4.10 gears over the 3.73.
Would it make that much difference goin the 4.10 's over the 3.73 's ?
I'ts not a DD but I still need to street & highway it at times.
I'm not worried about MPG's or I would not be rollin a K5 but a Geo with foggy headlamps and recycled milk container fenders.
Also should I go the 4.10 's front & rear or only rear ?
Currently D44 in front 3.07 & GM 12-bolt rear 3.08 gears.

 

[steve_kibbe]

You need to match the front and rear.

 

[beater_k20]

the only way you could run 33s and 4.10s in the rear, and 3.08s in the front would be to use a 25" tall tire up front. your gears need to be at least close.

 

[u2slow]

I'm running a '77 K5 350 / th350 / NP 203 - I'm currently running the factory 3.08 gears and I'm seriously considering the 4.10 gears over the 3.73.

I wouldn't worry so much about 3.73 vs. 4.10.

Instead, see which you can find in a 14bFF that's a bolt-in for your truck. Odds are the whole axle is going to be cheaper than regearing a 12-bolt.

 

[norville]

Thanks all for the input.

I guess now I need to decide

33 - no lift
33 - 2.5" lift
35 - 2.5" lift
35 - 4" lift

hmmm the problem is I have a cracked spring in the back. So I feel I should replace the rear springs instead of using blocks when lifted. But then that blows my wheel and tire budget for 35's.

The ranch 4" kit w/rear springs is just under $600 and that leaves only $500 for tires. If I go blocks the lift is $350 and then I can get 35's.


bob

 

[Muddytazz]

Go with front springs and a shackle flip n switch from DIY4X

 

[norville]

muddy, I'd still have to get new springs, and then drop the tank.

I guess I can just go blocks for now and then springs or shackle flip later on.

bob

 

[Cmoe]

I have this combo in my 74 k-5. My speedo doesnt work but when I am on the freeway it's wound up high.....

Post in the Classified section for stock rear springs wanted, if no reply call some junk yards about a rear spings (I would look for a pair unless your going to get them re-arched, so it sets level).

I thought I saw someone selling a full 4" lift in the sell section...

 

[MTMike]

I had that combo in my old '79 K10.... w/ a TH350 trans it was wound up at 3000rpms at 65mph.

 

[onetonbb74]

my 74 came stock with 4.10 and 31's. 33's should be better for freeway at 65mph. Getting double digits on mileage is hard to do when your at 3000 rpms with a 350 in a full size. My tahoe with no od gets 11 with a vortec and 3.73's and 33's. Good luck with the mileage.

 

[redbeast77]

Thanks fo the info! I've been thinking about doing just that with the 14bff idea. Either that od a D60 rear.

 

[norville]

I hope you folks don't mind, I'd like to bump this up for some more opinions.

thanks to all.


bob