are 3.08 gears good with 200r4? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**yote1234** · 10-17-2010, 07:41 PM

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 · 10-17-2010, 07:43 PM

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 · 10-17-2010, 07:45 PM

**yote1234** · 10-17-2010, 07:50 PM

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

clinebarger · 10-17-2010, 08:47 PM

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 · 10-17-2010, 09:03 PM

Quote:

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.

llowlife · 10-17-2010, 09:20 PM

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 · 10-17-2010, 09:27 PM

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.

clinebarger · 10-17-2010, 09:32 PM

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

Whoops

**yote1234** · 10-17-2010, 10:12 PM

Quote:

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.

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

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

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.

**yote1234** · 10-17-2010, 10:38 PM

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

vasquezmrysvll · 10-18-2010, 01:50 AM

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?

Jacfourteen · 10-18-2010, 05:26 AM

Quote:

Originally Posted by vasquezmrysvll

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.

CE20934 · 10-18-2010, 07:27 AM

Quote:

Originally Posted by vasquezmrysvll

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.

rsavage · 10-18-2010, 08:00 AM

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** · 10-18-2010, 10:43 AM

Quote:

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 · 10-18-2010, 10:44 AM

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 · 10-18-2010, 12:10 PM

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** · 10-18-2010, 12:52 PM

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

brothers69c-10 · 10-18-2010, 06:35 PM

no problem man

10-17-2010, 07:41 PM	#1
yote1234 Senior Member Join Date: Feb 2003 Location: Gold Canyon Arizona Posts: 4,265	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. __________________ 1971 K5 CST Blazer 1972 short super c10 1965 Chevelle Malibu 283 1968 Camaro 327 1968 Honda mini-trail z50a #377 1966 uh 1-D Huey

10-17-2010, 07:43 PM	#2
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,158	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. Smitty __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 71 C20 Longhorn/Ole Yellor 69 C30 Former Motor Home, Flat Bed time

10-17-2010, 07:45 PM	#3
bigguy69 dazed and confused Join Date: Jul 2008 Location: marion nc Posts: 1,649	Re: are 3.08 gears good with 200r4? __________________ members met: redbaron69, billsbowtie,nc67

10-17-2010, 07:50 PM	#4
yote1234 Senior Member Join Date: Feb 2003 Location: Gold Canyon Arizona Posts: 4,265	Re: are 3.08 gears good with 200r4? i understood the th350 and the 2004r 1st,- 3rd gears are the same? is this wrong? __________________ 1971 K5 CST Blazer 1972 short super c10 1965 Chevelle Malibu 283 1968 Camaro 327 1968 Honda mini-trail z50a #377 1966 uh 1-D Huey

10-17-2010, 08:47 PM	#5
clinebarger Senior Member Join Date: May 2009 Location: Fort Worth, TX Posts: 6,370	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.

10-17-2010, 09:20 PM	#7
llowlife Registered User Join Date: Jan 2010 Location: Elgin Mn Posts: 112	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. __________________ In the beginning of a change, the patriot is a scarce man, brave hated and scorned. When his cause succeeds however, the timid join him , for then it costs nothing to be a patriot. I am a revolutionary...so my son can be a farmer...so his son can be a poet. If there must be trouble, let it be in my day, so my child may have peace... 72 short step w/ 388 /4l80e/ and 3.08 gears.

10-17-2010, 09:27 PM	#8
bubba327 HOW long until spring?? Join Date: Mar 2009 Location: Star Idaho Posts: 1,413	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. __________________ 69 chevelle convertible 71-C-10 short-wide and low 64 C-10 custom shortbox "Bubba"s Recycling project"

10-17-2010, 09:32 PM	#9
clinebarger Senior Member Join Date: May 2009 Location: Fort Worth, TX Posts: 6,370	Re: are 3.08 gears good with 200r4? [QUOTE=68GMCCustom;4245909]I think you got 1st and 2nd ratios backwards on the t350. Whoops

10-17-2010, 10:38 PM	#11
yote1234 Senior Member Join Date: Feb 2003 Location: Gold Canyon Arizona Posts: 4,265	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 __________________ 1971 K5 CST Blazer 1972 short super c10 1965 Chevelle Malibu 283 1968 Camaro 327 1968 Honda mini-trail z50a #377 1966 uh 1-D Huey

10-18-2010, 01:50 AM	#12
vasquezmrysvll "the other guy" Join Date: Oct 2008 Location: Olivehurst California 95961 Posts: 901	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? __________________ God Said,"Building A 10 Second Import Is Like Coming Out Of The Closet, In The End Ur Still....."EXPLETIVE"

10-18-2010, 08:00 AM	#15
rsavage Registered User Join Date: Aug 2009 Location: Alden NY Posts: 2,705	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. __________________ 1961 C1 Corvette 1959 El Camino 350 TPI, 9" 4 w disc 69 Blazer K5 - sold July '20 2021 Durango RT 5.7

10-18-2010, 10:44 AM	#17
turp mcspray Registered User Join Date: May 2007 Location: Rapid City South Dakota Posts: 2,359	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! __________________ Turp Mcspray New life for an old 2wd, farm blazer http://67-72chevytrucks.com/vboard/s...d.php?t=505987 My Blazer build http://67-72chevytrucks.com/vboard/s...d.php?t=342299

10-18-2010, 12:10 PM	#18
brothers69c-10 Suburban Hick Join Date: Aug 2008 Location: Altoona, IA Posts: 810	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. __________________ Mathew 1947 Chevy 3600 1951 GMC 100 1969 Chevy C-10 396/500hp TH400 lowered 4" 1968 Imapla Custom 396/325hp TH400 "Grandmas Car" 1976 Crew Cab 4x4 diesel http://67-72chevytrucks.com/vboard/s...d.php?t=488505 1978 Chevy K-10 454 1983 S10 4x4 "Bumblb" (Grandpa's truck) 1993 Chevy S10 V8 conversion 1990 Ford Probe Gt 1992 Dodge W-150 "Old Man's Truck" 1992 Pontiac Grand Prix SE 1992 Mercury Grand Marquis-Mercruiser 2000 Ford F150 (Currently my mother drives this) 1946 Farmall H with Stan Hoist loader 1965 John Deere 110 1961 Wheel Horse " Rat Tractor"

10-18-2010, 12:52 PM	#19
yote1234 Senior Member Join Date: Feb 2003 Location: Gold Canyon Arizona Posts: 4,265	Re: are 3.08 gears good with 200r4? ahhhh... yea just stick with the 350th. thanx guyz......... __________________ 1971 K5 CST Blazer 1972 short super c10 1965 Chevelle Malibu 283 1968 Camaro 327 1968 Honda mini-trail z50a #377 1966 uh 1-D Huey

10-18-2010, 06:35 PM	#20
brothers69c-10 Suburban Hick Join Date: Aug 2008 Location: Altoona, IA Posts: 810	Re: are 3.08 gears good with 200r4? no problem man __________________ Mathew 1947 Chevy 3600 1951 GMC 100 1969 Chevy C-10 396/500hp TH400 lowered 4" 1968 Imapla Custom 396/325hp TH400 "Grandmas Car" 1976 Crew Cab 4x4 diesel http://67-72chevytrucks.com/vboard/s...d.php?t=488505 1978 Chevy K-10 454 1983 S10 4x4 "Bumblb" (Grandpa's truck) 1993 Chevy S10 V8 conversion 1990 Ford Probe Gt 1992 Dodge W-150 "Old Man's Truck" 1992 Pontiac Grand Prix SE 1992 Mercury Grand Marquis-Mercruiser 2000 Ford F150 (Currently my mother drives this) 1946 Farmall H with Stan Hoist loader 1965 John Deere 110 1961 Wheel Horse " Rat Tractor"



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