are 3.08 gears good with 200r4?

[yote1234]

im just trying to get an education! im almost done with my restoration (72 cheyenne factory 350/350th 3.08 open) and was kinda thinking about changing out the th350 for a 2004r. i would like the lower rpm at 55-75mph. also looking for better mpg. just wanted to get your imput on if i will loose/gain performance,mpg ect.

[71meangreenc10]

for what I have heard, no, its to low. 3.54-3.73 is what would make it more efficient with the 2004R.

Smitty

[bigguy69]

[yote1234]

i understood the th350 and the 2004r 1st,- 3rd gears are the same? is this wrong?

[clinebarger]

Gear ratios of the 2004R are: 2.74 first, 1.57 second, 1.00 third, .67 fourth.
TH350 ratios= 1.52 first, 2.52 second, 1.00 third.

I also recommend running a higher numerical gear than a 3:08 with any GM overdrive.

[68GMCCustom]

Originally Posted by clinebarger

Gear ratios of the 2004R are: 2.74 first, 1.57 second, 1.00 third, .67 fourth.
TH350 ratios= 1.52 first, 2.52 second, 1.00 third.

I also recommend running a higher numerical gear than a 3:08 with any GM overdrive.

I think you got 1st and 2nd ratios backwards on the t350.


I will be running a 200-4r and have 3.73 gears. My truck had 3.08's with the first motor and I got 3.73's. They were great with the 383 stroker I just took out...but turned 3k or so on the freeway. With the 33% OD....I'm thinking 3.73's will be about right....though 4.10's might be better fitted for what I'll be doing with it.

[clinebarger]

[QUOTE=68GMCCustom;4245909]I think you got 1st and 2nd ratios backwards on the t350.


Whoops

[llowlife]

I'll let you know in a week or 2 if you are still interested. I have a 388 with a 4l80 and 3.08 I suspect I will be going for 3.42 or so this winter just so I can get some more snap but for now it was a posi in teh truck when I bought it.

[bubba327]

Do not forget that tire size makes a difference also.That going from a 235/60/15 (26.1") to a 235/70/15(28") is difference of over 200 RPM at 55 mph. Find a Free online RPM gear calculator and plug in your numbers to get RPM's
In my 64 with the 235/60/15 tires and TH350 with 3.73 gears , I am screaming at 65 mph and freeway 75mph is Impossible.
Just bought a 3.07 rear end to install.

[rsavage]

I have a 70 Burb with 3.07's that I put a 200 4R in. For non-highway type driving, I don't use OD, just 3rd with a dash switch to lock up the torque converter when it shifts into 3rd. On the highway, the OD works fine. It turns about 1750 rpms at 66 mph on 235/70/15 tires. 3.73's would be ideal, I think, but your 3.08's will work if used as a 3 speed auto when not on the super slabs.

[yote1234]

Originally Posted by rsavage

I have a 70 Burb with 3.07's that I put a 200 4R in. For non-highway type driving, I don't use OD, just 3rd with a dash switch to lock up the torque converter when it shifts into 3rd. On the highway, the OD works fine. It turns about 1750 rpms at 66 mph on 235/70/15 tires. 3.73's would be ideal, I think, but your 3.08's will work if used as a 3 speed auto when not on the super slabs.

the problem is most all my driving is under55mph. rarly get on the freeway.
so i guess i'll keep the 350t.h. and save the money! yea! save the money!
thank you all for your repllies! and opionions! great info... dave

[turp mcspray]

I think the 200 has a .67 overdrive. Multiply that, times any gear ratio, and you will see what it would be equall to with a th350. (Example...3.08 x .67 = 2.06. .67 x 3.73 = 2.50) 3.08s would be great if you have a TON of low end torque to pull it in overdrive, or want to cruise at 100 plus all day! But then wind resistance would wipe out any mileage increase anyway.LOL!

[brothers69c-10]

you could always just leave the th350 in and put like 2.73's or 2.56's in the rear end. It would have the same effect.

My 68 impala has a 396 325hp, th400 and 2.56 rear gears. Gets 18mpg in town.

[yote1234]

ahhhh... yea just stick with the 350th. thanx guyz.........

[brothers69c-10]

no problem man