Rear Axle: Best ratio behind a 700 r4

[toastervet]

I'm thinking about putting a 700 R4 in my 53 commander.I intend to swap out the stock engine with a high performance 289. What do you think would be the best rear end ratio for this set up?

[bige]

I had the 3.73 with the 700 in my Avanti. Lots of fun off the line, quiet economical cruise.

[Leosnake]

I have a 3.50 with mine....HATE IT !!! I'm changing the gears to 3.70 or 3.90 range in the near future!

[wittsend]

I have a 3.50 with mine....HATE IT !!! I'm changing the gears to 3.70 or 3.90 range in the near future!

Oh no! I have 3.07's (and taller 225-60-16 tires too). Not on the road yet. Maybe the 350 Chevy will make the difference. What has me baffled is when people say they have a 700R4 and 3.73 and the like gears. The 700R4 has a 3.09 1st gear. Are you guys pulling stumps or something??? I understand about the complaint of the 1-2 shift being steep. But with the mentioned 3.73+ rear ratios it seems like 1st gear can just be skipped. The Camaro's came 3.07's and 2.73 was an option. Must have turned all of 1,200 RPM back when 55 MPH was a mandatory speed limit.

Toastervet, use one of the on line calculators. They factor in the tire size, rear ratio and allow you to see the RPM/MPH figures.

Tom

[bige]

I would be interested to know what you don't like about the 3.50 and the 700? When GM installed them most were used with ratios under 3:00.

I've had experiences with both the 200 and the 700 in the same car.

I had it at the drag strip with both transmissions and it ran basically the same times. It was more fun to drive with the 700. My R2 Avanti was mildly modified but not a torque monster. The 1-2 shift rpm drop was not a factor as evidenced by the 1/4 times being within a few hundredths of each other.

Fitment was better with the 200 but other than that in real world driving the 700 was more fun.
ErnieR

[Swifster]

the 700R4 is the same as the 4L60 and the 4L60E. Most 93 and up Camaros had 3.42's in them. A 3.31, 3.54 or a 3.73 should be fine.

[sweetolbob]

the 700R4 is the same as the 4L60 and the 4L60E. Most 93 and up Camaros had 3.42's in them. A 3.31, 3.54 or a 3.73 should be fine.

I have a 4:10 behind a 200R4 in my 83 Avanti and it doesn't spend much time in first. Unless you are going racing, a 3:42 ratio is about what I'd put in. You are not trying to get a large, heavy car moving. My 54K has a 350/700R4/3.42 and that's a pretty happy combo but I'm running much larger tires than stock.

If you have a low number 3: or so, try it first before you make a change then you'll have the data to hit the correct ratio for your driving. Remember that later model cars use bigger tires than you have so that will change the effective gear ratio.

As an aside, recall that a complete rear end rebuild (you remove it from the car) will set one back about $900 if you use a posi and I recommend one. Replacing a gear ratio under the same conditions will cost $3-400 ($150 gear set + installation) so unless you do your own work guessing can get expensive.

Bob

[Jessie J.]

A lot depends upon the general terrain of where you live, how far you regularly drive, and your driving style.

For running into town for car shows, trips of less than 200 miles, blasting through the hills and valleys, or a bit of play at the drags, a 3.73 or 3.50 ratio is good for keeping a grin plastered on the 'ol kisser.
But if one lives in the wide open spaces, or intends to regularly make 500+ mile trips by expressway, crusing at a steady 75-80, gears in low 3.00 range will to most be more satisfactory.
This is what is so great about having a axle with a drop out center section. Once you have two pigs set up, a floor-jack, jack-stands, a set of sockets, and an hours time and you can swap in the best gearing for either a 1/4 mile run, or a 2500 mile vacation trip.
_That is if you don't mind being a greasy hot rodder

That said, with normal 15" size tires, I've been most satisfied most of the time with running 3.43s behind the 700R4, and what I'd go with if I had only one choice.

[PackardV8]

I intend to swap out the stock engine with a high performance 289. What do you think would be the best rear end ratio for this set up?

All depends on what is the goal and what is the budget.

The other factor not yet mentioned is the camshaft duration. A high performance 289" is sort of an open ended description. Recently I was asked to build two of them. One was a semi-dished piston R1. It would be fine with a 3.43 rear gear. The other was an R3 clone with a roller camshaft. It would need at least 3.73 and better gears to keep the RPMs up where the camshaft does it's business.

I'd estimate the mild R1 with 3.31 gears and the 700R4 would get around 18-20 MPG at highway cruise. The R3 clone would only get 10-12 MPG at best, but it should be able to match the 172 MPH of the R3 prototype.

All depends on what is the goal and what is the budget.

jack vines

[Gunslinger]

When I had a 700R4 installed in my '70 Avanti, the shop doing the work needed to know the cam specs, rear axle ratio, weight of the car and engine power. It was a new GM Performance 350HO crate engine, so the specs were easy to look up. They asked me the approximate weight of the car and the rear axle ratio which I knew to be 3.31. I knew about the weight of the car is.

The 700R4 will smoke the tires in most any gear, but that's probably as much due to the forward weight bias in the car than anything else.

[Swifster]

The rear gear will effect your mileage. I have a 2001 Ranger with a 3.0L, automatic and 3.73's. My buddy had a 2002 Ranger with a 4.0L and 3.55's. He averaged anywhere from 2 MPG to 4 MPG more than I did. If you're using a Dana 44, I'd go with a 3.54.

[plwindish]

My 76 Avanti has a 3:31 behind a warmed up 400 / 200 R4 combination. That is a very good set-up to drive with. 2000 rpm's is showing 70 mph in the OD. There is more than enough power to do what you want to legally or illegally.

[RadioRoy]

You have to calculate the final drive ratio when the car is in overdrive. Studebaker equipped the majority of its 289 overdrive equipped cars with the 3.73 ratio rear end. In overdrive, that final ratio comes to about 2.46.

My 259 overdrive 56 wagon has a 3.92, which calculates to about 2.59 final ratio. The engine has less torque than a 289 and the station wagon often hauls a heavier load than a coupe or sedan

You also have to figure in the diameter of the stock wheels and tires. I bet many of the later Chevy's had 14 inch wheels and therefore smaller tire diameters than Studebaker did.

You also have to look at the sweet spot of the individual engines - the RPM they are happy running all day. The Studebaker 289 probably has a different sweet spot from a Chevy or a Ford.

[Swifster]

They are smaller diameter tires, but the wheels are larger...

1964 Studebaker Daytona - Tire Size 6.70x15 - Diameter 27.50"
1987 Buick Regal T-Type - Tire Size 215/65R15 - Diameter 26.02"
1993 Chevrolet Camaro Z-28 - Tire Size P235/55R16 - Diameter 26.1"
2002 Chevrolet Camaro SS - Tire Size P275/40ZR17 - Diameter 25.6"

Newer cars have larger wheels to slow down rotation. This is equalized by the smaller diameter tires. I think the tire issue is a non-factor.

[PackardV8]

You have to calculate the final drive ratio when the car is in overdrive. Studebaker equipped the majority of its 289 overdrive equipped cars with the 3.73 ratio rear end. In overdrive, that final ratio comes to about 2.46.

My 259 overdrive 56 wagon has a 3.92, which calculates to about 2.59 final ratio. The engine has less torque than a 289 and the station wagon often hauls a heavier load than a coupe or sedan.

Yes, the Studebaker engineers pretty much knew the sweet spot for power versus gear. Can't go wrong with the OEM numbers. Changing from that is for special circumstances - much highway cruising on flat ground or max quarter mile acceleration or whatever. Most Stude cars with overdrive have a T86 which has a .70 overdrive, so a 3.73 = 2.61 in overdrive and a 3.92 = 2.74.

Yes, a wagon with a 259" needed more gear, but Stude also put the 3.92 rear gear in the 56 GH with the big Packard V8 and T85; with the .72 overdrive, it was at 2.82. It would smoke 'em off the line and still pull 130 in the top end floored.

jack vines