Ring and pinion or new tranny? Help!

[Mick65]

Hi all,

I've been considering getting a new ring and pinion put in my truck but it turns out I have a 4 series rear end. Theres currently 4.11 gearing in the rear end and I have a 4 speed saginaw transmission.

My question is would you guys suggest for me to drop the 800-1000 on a 3 series rear end in order to get it down to a 3.08 or so.

OR

Should I keep the 4.11 gearing and get a transmission with an overdrive... If so, what would be the easiest/least expensive way to go about this.

Thank you!

[shortbed70]

What do you do with the truck? If you work it hard I would swap gears. If it's a cruiser trans all the way...

[Mick65]

It's just a daily driver. To and from work. Little bit of highway use.

[61_FL_Apache]

I have a 3.08 with a TH350 and for around town its great and some on the highway.. Im not sure what the final gear ratio is for your trans, but you can consider the 3.73 and 3.08 for your application.

A new rear gear would be the cheaper option too.

[shortbed70]

Depending on tire size also... Most 4 speeds are 1-1 ratio so the rear will be say trans will turn 3.73 turns to one turn of tires... I can say from experience a 3.73 and 26" tire isn't fun trying to stay with today's speeds. 3.42 gear and a 4 speed would be great with a 26" -28" tire maybe 3:55 29-30 might be good. Gears gonna run around 500 for gear and kit... Trans gonna b double easily

[Mick65]

Originally Posted by shortbed70

Depending on tire size also... Most 4 speeds are 1-1 ratio so the rear will be say trans will turn 3.73 turns to one turn of tires... I can say from experience a 3.73 and 26" tire isn't fun trying to stay with today's speeds. 3.42 gear and a 4 speed would be great with a 26" -28" tire maybe 3:55 29-30 might be good. Gears gonna run around 500 for gear and kit... Trans gonna b double easily

Yeah my transmission has a 1:1 ratio. My tires are 27.5".

[Clyde65]

Get you a T5. You can snag one for under 500 I bet, new clutch and a resurface, your good then

[Sharps40]

Several fellas, including me, getting their T5 Transmissions and advice on install/use from Tom Langdon at Stovebolt Engine Company, MI.

I'm about to put a T5 Astro Trans behind my 250 I6. Tom has great info on their strength and the install depending on whether you pick the S10, Astro or Camaro versions. He rebuilds them all before they go out....$450 and up. My Astro was $670 with short shift conversion.

[kieth]

Originally Posted by Mick65

Hi all,

I've been considering getting a new ring and pinion put in my truck but it turns out I have a 4 series rear end. Theres currently 4.11 gearing in the rear end and I have a 4 speed saginaw transmission.

My question is would you guys suggest for me to drop the 800-1000 on a 3 series rear end in order to get it down to a 3.08 or so.

OR

Should I keep the 4.11 gearing and get a transmission with an overdrive... If so, what would be the easiest/least expensive way to go about this.

Thank you!

I think I have all the information we need on your truck, send me your email and I will send you a spread sheet that shows speeds with all rear axle ratios and transmissions, it also shows torque to the ground so you can make sure the truck does not fall on its face.....oh the only info I need additional is the engine you are running and the hp......Kieth

ps need e mail because I cannot post a excell spreadsheet to this forum.

[kieth]

With the tire size you are running the 3:08s by themselves will not help, I always try to look at my rpm at 2000 rpms (shoot for 2000rpms at 65mph) depending on the engine folks are running. If you do the 3.08 and change the trans to a t5 as long as you have enough torque it will get you to the best range of speeds. If you have 200 hp the truck should have enough torque to function going down the highway . If you plan on pulling a trailer you would of course have to stay in 4th gear and raise rpms a lot to maintain road speed. Kieth

Ratio:...4 speed......T5....................speeds shown at 2000 rpm
4.11.....40 mph......50
3.08.....54mph.......66mph
3.73.....44mph.......55

[kieth]

Hey mick65 give me a call to discuss the spreadsheet, it is a little intimidating but there is lots of info contained in it. Kieth

[66Submarine]

My father has a truck with a Saginaw 4 speed (3.11 first gear) and 3.07 gears with 31x10.5r15 rear tires. Motors right down the road; 70MPH @ 2,500RPM. Works pretty well IMO; decent around town, too. (Engine is a basic flat top 350 with vortec heads)

[kieth]

Originally Posted by 66Submarine

My father has a truck with a Saginaw 4 speed (3.11 first gear) and 3.07 gears with 31x10.5r15 rear tires. Motors right down the road; 70MPH @ 2,500RPM. Works pretty well IMO; decent around town, too. (Engine is a basic flat top 350 with vortec heads)

This shows how different components dramaticly effect the performance (speed) of a truck. The really tall rear tires effectively are like having a OD transmission. What is the height from the ground to the top of the tire in inches, I will reload the info and see if agrees with how your truck performs. Kieth

guessing your tire height at 30" my speed chart shows 72mph at 2500rpm for this truck, the real difference shows up in the available torque

3:08, 1:1 trans ratio, 30" diameter, 300 hp 350, torque to grnd 606ftlbs

3:08,......................,.27.5" dia tires, 200hp,........torque to grnd 588ftlbs

3:08, t5 .80 ratio......,27.5" cia tires, 200hp,.......torque to grnd 470ftlbs

This is why I developed the spreadsheet which shows torque within a usable range of speeds.......what on the surface looks like the same set up can perform differently depending on engine hp, trans ratio, rear axle ratio, and importantly rear tire diameter.....a truck with only 200 hp has almost the same torque available due to the smaller diameter rear tires...as a 300hp truck with taller rear tires......

[66Submarine]

Loaded diameter is about 29" IIRC.

I'm not sure I understand though. 27.5 to 30 is only a roughly 9% increase; how are you coming up with nearly the same figures for 200HP with a 27.5" tire as 300HP with a 30" tire? At any rate foot pounds are a set measure of the rotational force and wouldn't change with a change in leverage (tire size), do you mean thrust/linear force?

I would personally probably figure things like this;
50MPH=1,800RPM
Engine torque @1,800=350ftlbs
12 divided by 14.5 tire loaded radius=.83
350x.83=290
290x3.07=890 pounds linear force @ 50MPH (of course only theoretical and as such does not account for driveline losses, etc)

If I increase the engine speed to what it would be with 3.73 gears (about 2,100RPM) I get this;
50=2100
2100=360ftlbs
360x.83=300
300x3.73=1,120 pounds of thrust/linear force

So I get a 26% increase in force, but with a 22% increase in reduction. I don't see how you can get nearly the same output from 200HP as you can with 300HP only increasing the reduction by 9%. (Assuming similar torque curves between the two engines)



BTW, anyone want to check me on all that? I'm not much of a math wiz, lol.

[familyfast64]

No way does that mean those torque numbers to ground... Does it? My nova had a t10 1:1 fourth gear with a 3.08 and a 275/60/15. And I can't fathom my 355 even putting close to that down. Perhaps I'm missing it but I think something's wrong. I'm listening tho...

My 383 now with the th350 and Mt Indy n-50s turn60 mph at 2400 rpm and70 at2750 rpm. Can we figure rear end ratio and these torque to ground numbers? I can't imagine how without knowing hp n tq numbers of engine. I also don't even know the final drive in the th350.. lol

[66Submarine]

Not torque as in flywheel torque measured at the wheels; torque as in actual rear axle shaft torque. (Or thrust/linear force in my example) The gear reduction increases the torque, but reduces speed. As an example (forgetting drivetrain losses again) in first gear my 2bbl 283 powered truck with a SM420 four speed and 4.10 gears puts out over 7,000ftlbs of torque @ the axle shafts. And the acceleration is truly brutal... for the first 10MPH.

BTW final drive in TH350 is 1:1, as are most all transmissions that do not have OD.

Just for laughs, imagine a 20% drivetrain loss and a truck with 5.14 gears, a SM420 and something with 400ftlbs - roughly 12,000ftlbs of theoretical axle torque!

[familyfast64]

Wow, that's crazy. I've got a lot to learn.