Technical 200R4 vs TH350 GEARING ISSUE

Need some help with a gearing issue.
Currently have 57 Chevy Truck 327 small block, TH350 trans, running 3.91:1 ring and pinion.
Need to run about 60 mph at 2000 rpm. Not possible with current set up.
Not many options for new ring and pinion other than 3.38:1 or changing to Ford 9 inch.
I know the 3.38 will not get me where I want to be.
IF I change the transmission to 200R4 will it work better than the rear end swap?
Thanks for any help you can offer.
Jim

 

go to a site that has a calculator comparing transmissions/rear gears/tire size/etc like project33.com

 

I'd do the 3.38 swap and a 700r4 swap. Then you should be able to run a wide range of tire sizes for the desired RPM

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3.9 x .67 = 2.61

 

A 200-4R has an overdrive ratio of 0.67:1. If you multiply that by your current rear end ratio of 3.91:1 you get 2.62:1.

In top gear, it would be like the TH350, if you swapped to a 2.62:1 ring and pinion.

Just take your current RPM at 60 and multiply it by 0.67. That's what a 200-4R gets you.

 

We have the 3.73 rear gear in our 55 with a 700r4 and 205/70R15 tires and it runs 2200

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We did a 55 with a 4L60E, 3.31 rear 205/70R15 tires and it runs 1880 at 60.

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Actually, you will lose about 300 more RPM with the lock up converter too.

 

If money wasn't an issue. I would swap a 700r4 and a ford 9 inch running 3.73 gears.

 

I've a 200R4 with a 3.73 rear end and rears at 29.40 (or about, doing it from memory) and run 75 mph at 2100 rpm. in OD. I used that ****** as my set up was for a TH350 so the only thing I had to do was weld the rear support in a dif. location as the two are the same length...drive shaft worked fine and there were no issues with the ****** hump etc.
I like the hell out of it as I do a lot of highway driving in Az.

 

The 700R4 has a top gear of 0.70:1
3.73 x 0.70 = 2.61 (2.611)

The 200-4R has a top gear of 0.67:1
3.91 x 0.67 = 2.62 (2.6197)

That would be a lot more work for 0.0087:1

The only possible advantage possibly would be the lower first gear on the 700R4, to get the weight of the truck moving.

 

Something to think about...
Unless you've done a bit of engine design (hard parts) homework...not many - if any...small Chevy's are very efficient pulling freeway speeds at 2000rpm, unless you have about a 1200lb car (with driver and p***enger)..!
Might look at raising that rpm to 2400/2600rpm...the engine might be a bit happier at a slightly higher rpm.

Mike

 

depends on the engine. Stock cam, Qjet carb, etc and it will do fine. Chevy went to some wild gear ratios in the late 70s, before they got overdrive automatics. 2.29 2.41 etc, and they got pretty good mileage. They cruised fine, but were dogs off the line.

 

Also the 200R is not a good truck transmission unless it is a look at me truck. They are a good transmission but not made to take a real load.

I would do a ring and pinion swap unless I didn't have that option. But I am not a big fan of AOD in general. So my opinion is probably moot.

 

They can be built to take 1000hp for under $3k. $2199.99 gets you one that can handle 500hp.

If you top out at just 400hp you can get one for $1699.99.

If you roll-your-own, you can have that 400hp one for the price of a used one, and $600.

AOD was a great band, until their demise in 1986. I was lucky to see them a reunion show a number of years later.

 

Stock they are not what I would put in a truck and before I built a 1600 dollar ****** (plus the core) I would change the ring and pinion and motor on.

yes they can be built and the measurement is like measuring HP, in dollars.

That said we ran one for several years in the Raven's roadster. Until he drove the motor the way I had been telling him to drive the motor, then it came apart. But it was cool that one time.

 

No core charge.

 

The new parts are useless without a case.

The 200 is preferred over the 700 around here any more. They used to be a dime dozen but not any more. The 700 is actually an easier swap if you already have a long tail 350 in there.

I don't care for the feel of either one of them. I don't mind an OD stick so much. I just don't like the feel of the auto overdrives from that era. Come to think of it I don't like an auto with a really loose converter either, if you got that much cam get a stick and learn to drive it.

 

From what I've been able to uncover, 55 to 62 Chevy Truck you had two choices for ring and pinion gears 3.9:1 and 3.38:1.
3.9:1 was by far the most common.
Can anyone confirm that as truth?

 

Overdrive was only offered a couple years. The 3.90 ratio was by far the most common.

 

I have the 200-4R in the 35. It's a 350 with a 3.55 rear gear and a 28.5" tire. Average at 70 is 2,000.


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