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Old 10-17-2010, 06:41 PM   #1
yote1234
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are 3.08 gears good with 200r4?

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.
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Old 10-17-2010, 06:43 PM   #2
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Re: are 3.08 gears good with 200r4?

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

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Old 10-17-2010, 06:45 PM   #3
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Re: are 3.08 gears good with 200r4?

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Old 10-17-2010, 06:50 PM   #4
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Re: are 3.08 gears good with 200r4?

i understood the th350 and the 2004r 1st,- 3rd gears are the same? is this wrong?
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Old 10-17-2010, 07:47 PM   #5
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Re: are 3.08 gears good with 200r4?

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.
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Old 10-17-2010, 08:03 PM   #6
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Re: are 3.08 gears good with 200r4?

Quote:
Originally Posted by clinebarger View Post
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.
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Old 10-17-2010, 08:20 PM   #7
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Re: are 3.08 gears good with 200r4?

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.
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72 short step w/ 388 /4l80e/ and 3.08 gears.
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Old 10-17-2010, 08:27 PM   #8
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Re: are 3.08 gears good with 200r4?

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.
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Old 10-17-2010, 08:32 PM   #9
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Re: are 3.08 gears good with 200r4?

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


Whoops
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Old 10-17-2010, 09:12 PM   #10
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Re: are 3.08 gears good with 200r4?

Quote:
Originally Posted by clinebarger View Post
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.

soo it looks like 1,2,3 gears the same with higher 4th. ...........





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





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.[/QUOTE

please keep me posted... thx






Quote:
Originally Posted by llowlife View Post
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.
in thinking it will be the same in 1st,2nd,3rd with better overdrive.. keep me posted also.. thx






Quote:
Originally Posted by bubba327 View Post
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.
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Old 10-17-2010, 09:38 PM   #11
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Re: are 3.08 gears good with 200r4?

i guess what im saying if i had changed my 350th to a 200r4. in 1st,2nd and 3rd gears the performance shouldnt change at all, but at hiway speeds in 4th it should save rpm's and fuel.

it's a very stock truck not a speed demon... dave
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Old 10-18-2010, 12:50 AM   #12
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Re: are 3.08 gears good with 200r4?

i dont really understand why my 85 iroc came with 2.73 rear gear, 700r4 and 245/50r16 if everyone says 3.08's are too numerically low?
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Old 10-18-2010, 04:26 AM   #13
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Re: are 3.08 gears good with 200r4?

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Originally Posted by vasquezmrysvll View Post
i dont really understand why my 85 iroc came with 2.73 rear gear, 700r4 and 245/50r16 if everyone says 3.08's are too numerically low?
Wow that is really high geared! Was OD usable? If so it probably was because a camaro is quite a bit lighter and more aerodynamic. Most people who have done the OD 3.08 combo with trucks like ours tend to lose MPG because they say the motor is chugging too hard to push the brick-like aerodynamics down the highway.
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Old 10-18-2010, 06:27 AM   #14
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Re: are 3.08 gears good with 200r4?

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Originally Posted by vasquezmrysvll View Post
i dont really understand why my 85 iroc came with 2.73 rear gear, 700r4 and 245/50r16 if everyone says 3.08's are too numerically low?
Two words: fuel economy. With that tall of a rear end coupled with that deep of an overdrive, the engine would be barely ticking over during flat cruising/fuel economy testing. Low RPM + light throttle = high mileage. When I bought my '89 Caprice, it had a 305/700-R4/2.73 & 235/60R15s.* 2000 RPM was 81 MPH, so 55 wasn't even 1500.

Come to think of it, there was even a 2.56 available for the B-bodies. My Gramma's '88 has that one.


*From the factory, it was a 305/200-4R/2.73 with 205/70R15s.
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Old 10-18-2010, 07:00 AM   #15
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Re: are 3.08 gears good with 200r4?

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.
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Old 10-18-2010, 09:43 AM   #16
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Re: are 3.08 gears good with 200r4?

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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
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Old 10-18-2010, 09:44 AM   #17
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Re: are 3.08 gears good with 200r4?

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!
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Old 10-18-2010, 11:10 AM   #18
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Re: are 3.08 gears good with 200r4?

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.
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Old 10-18-2010, 11:52 AM   #19
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Re: are 3.08 gears good with 200r4?

ahhhh... yea just stick with the 350th. thanx guyz.........
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Old 10-18-2010, 05:35 PM   #20
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Re: are 3.08 gears good with 200r4?

no problem man
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