Do the 3:08's have to go??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Red 69 C-10 · 09-10-2007, 04:35 PM

Hey gentlemen,some of your thoughts please. Got a 69 w/ 350 all stock sept' for Performer intake,600 cfm Edelbrock,HEI,cast iron exht. with 2.5 pipe and 400 T/H trans.Rear end is 12 bolt full of 3:08's. This thing won't get out of it's own way from dead stop hardly. Forget bout pulling my bass boat or jet boat to the lake.I am thinking I'll have to put the 3:73 rear end backin, hate to do that. Those 3:08's are quite and soo smooth and sure get better mileage. Any thoughts truely appreciated....Thanks

67_C-30 · 09-10-2007, 04:44 PM

I think you have another problem. My red 69 C-10 has 3.08's with a stock 350 with a Q-jet and a TH-350 and it will spin the tires easily from a dead stop, and pulls my car trailor and race car decently. It is not an all-out power house going up a long grade with a car on the trailor, but it does OK. Its sounds like you might have a timing or carb problem if its that much of a dog, unless the engine is very tired.

BTW,

to the board!

**Palf70Step** · 09-10-2007, 06:03 PM

my 69 POS parts truck with a smog motor 305/T350C/3.08s would smoke them without hesitation. Sounds like there are other issues, maybe tranny issues.

Ackattack · 09-10-2007, 07:02 PM

Sounds like a tuning problem to me.

If it's not, then a good (but possibly pricey) option is 3.73s with a OD tranny. I'm now getting 18.5 mpg out of mine (but it's also fuel injected)

PanelDeland · 09-10-2007, 07:04 PM

Red, I think they are right.Either that or you're expecting too much.In the long run you may want to consider a 700R4 for it though.You will need a 3:73 for that.3:08's were the standard gear for auto's so it should run and tow a boat with no problem.

Bowtie001 · 09-10-2007, 07:31 PM

One more vote for "it's not the gears". My 84 with a 350 and 3.08's and a th-350 got up fairly quickly. Bring it to the dragstrip and do some tuning... mine ran something like 17.10s stock. Timing and carb are the areas to look for... make sure that the butterflies are opening fully, that's surprisingly easy to miss. Also make sure your secondaries are opening.

-Brian

glock35ipsc · 09-10-2007, 09:57 PM

with the rest of these guys.

**special-K** · 09-10-2007, 10:04 PM

Get rid of the power robbing TH400.You don`t need it with what you have,anyway.

samwise68 · 09-10-2007, 11:21 PM

i have 3.07's behind my 307 and 3 speed, and i can catch rubber in both 1st and 2nd gear, and probably 3rd if i reallllly tried. but, still.

i agree. gears should be good. you won't be launching like with 4.56 out back, but, still should have some get up.

-Sam.

Orange · 09-11-2007, 07:56 AM

Quote:

Originally Posted by glock35ipsc

with the rest of these guys.

x2.

Quote:

Originally Posted by PanelDeland

Red, I think they are right.Either that or you're expecting too much.In the long run you may want to consider a 700R4 for it though.You will need a 3:73 for that.3:08's were the standard gear for auto's so it should run and tow a boat with no problem.

Why are 3:73's needed for a 700R4? I have the stock gears with mine, and all is well.

(Standard truck gear is actually 3:07 isn't it?)

DLB

Dean · 09-11-2007, 08:57 AM

Just put a 5.14 in my 55 Chevy and that did the trick......lol I could pull stumps if necessary..............

sleepyboy · 09-11-2007, 09:06 AM

I like my 3:08s

Putter · 09-11-2007, 09:56 AM

3.08s here as well....Had 3.73s in there, but needed more interstate speeds. Swapped with GMan. I can do a descent scratch from a dead stop. Agree you may have other issues.

68gmsee · 09-11-2007, 07:39 PM

Red 69 C-10, one more for the "it's not your rear end" vote.

FYI: I have a 69 with a tired 350ci with quadrajet and 350 trans with 3.07 rear end. Some years ago I pulled an 18' trailer loaded with a full size tractor, bush hog and other equipment for about 100 miles and had absolutely no problem towing.

I also have towed other vehicles, trailer full of lumber, etc. with it and haven't had any problems. As others mentioned, it could be carb, tuning, transmission, or engine.

At my age I'm not into peeling out for the fun of it, but I've stepped on it on occasion to "blow it out"

and it has enough power for me...

jfalesi · 09-11-2007, 09:00 PM

What is your RPM in OD at highway speed? I looked into this a while ago when I was considering a swap. I even whipped up a spreadsheet that shows RPM at a given speed in a given gear with different combinations of transmission and rear ends. It was fun. I'm a geek.

Quote:

Originally Posted by Orange

x2.

Why are 3:73's needed for a 700R4? I have the stock gears with mine, and all is well.

(Standard truck gear is actually 3:07 isn't it?)

DLB

Bowtie001 · 09-12-2007, 08:14 AM

I think we've overwhelmed the poor guy.

First off, I forgot to welcome you to the site.

Secondly, want any help getting to the problem?

-Brian

68gmsee · 09-12-2007, 08:26 AM

Quote:

Originally Posted by Bowtie001

I think we've overwhelmed the poor guy.

First off, I forgot to welcome you to the site.

Secondly, want any help getting to the problem?

-Brian

Yeah, forgot that also...

I guess you find out quick enough how many people read this site...

Orange · 09-12-2007, 10:26 AM

Quote:

Originally Posted by jfalesi

What is your RPM in OD at highway speed? I looked into this a while ago when I was considering a swap. I even whipped up a spreadsheet that shows RPM at a given speed in a given gear with different combinations of transmission and rear ends. It was fun. I'm a geek.

Working on getting a new instrument cluster.
Ask me in a year.

(New baby in the house = no funds).

DLB

mnunn454 · 09-12-2007, 06:35 PM

Maybe a trip to the local chassis dyno is in order. For about $150 (here in RI) they'll tune carb and timing to provide optimal performance for your normal requirements.

Without knowing the details, were it me, I'd attack the issue in this order
Tuneup (plugs, wires, ignition module, coil, free breathing intake etc)
Carb a/f ratio (you want 14.7:1 when cruising and 12.5:1 when mashing on the gas),
Timing (run as much advance as you can w/o pinging or hard starting),
Exhaust (minimal back pressure, especially the mufflers),
Cam design (profile) and adv/retard,
Cam health (are the lobes worn off? Are the timing chain/geears worn?)
Heads (both flow and compression ratio),
Torque converter stall
Swap the tranny for a TH350 or TH200
Change the R&P ratio to a 3.42 or 3.73

corn · 09-12-2007, 06:53 PM

This winter Im swapping my 3:07's for 3:73's. Its my toy & the gears will make it more fun.

brianthelion02 · 09-12-2007, 07:28 PM

I agree with start with the basics,tune up and all that maybe even a compression check is in order!!!!!And personally i believe a 700r would be good in youre situation!!!700r have a lower 1st gear which is what you need for that bass or jet boat!!!!And the od will sure help with mpg!!!!! I also never saw anything about tire size,assuming youre near stock size tire?Good luck and let us know what ya find!!!!!!!

Red 69 C-10 · 09-15-2007, 08:27 AM

Gentlemen, want to thank all you for taking time to address my problem. Going to advance the snot out of it till she pings,lean the primaries and see how she runs. Good to hear from all you. Thanks a bunch.....

Bowtie001 · 09-15-2007, 11:11 AM

Do yourself a favor and make sure that the butterflies are open all the way under WOT. This is surprising, but it makes a BIG difference obviously.

Robznob11 · 09-15-2007, 11:23 AM

well i had a chevy 6 cylinder that lost all its get up and go and found out that i neeeded to change the advance kit, you can get a performance advance kit from auto zone,napa,etc(@$15) looks like two little dog legs and a bunch of different springs they go under the distributor cap, start with the lightest ones and if it pings go to the med, lighter the spring the more advance. when i changed mine they visualy looked great but the car got so bad it would bog itself going up a hill, after i swaped them out i could light up two 8 in tires with a tired 200 v6

Jcentsr6 · 09-15-2007, 12:47 PM

welcome....and check your carb.

09-10-2007, 04:35 PM	#1
Red 69 C-10 Registered User Join Date: Sep 2006 Location: California Posts: 11	Do the 3:08's have to go??? Hey gentlemen,some of your thoughts please. Got a 69 w/ 350 all stock sept' for Performer intake,600 cfm Edelbrock,HEI,cast iron exht. with 2.5 pipe and 400 T/H trans.Rear end is 12 bolt full of 3:08's. This thing won't get out of it's own way from dead stop hardly. Forget bout pulling my bass boat or jet boat to the lake.I am thinking I'll have to put the 3:73 rear end backin, hate to do that. Those 3:08's are quite and soo smooth and sure get better mileage. Any thoughts truely appreciated....Thanks

09-10-2007, 04:44 PM	#2
67_C-30 I have a radical idea! Join Date: Jan 2005 Location: Sweet Home Alabama! Posts: 6,513	Re: Do the 3:08's have to go??? I think you have another problem. My red 69 C-10 has 3.08's with a stock 350 with a Q-jet and a TH-350 and it will spin the tires easily from a dead stop, and pulls my car trailor and race car decently. It is not an all-out power house going up a long grade with a car on the trailor, but it does OK. Its sounds like you might have a timing or carb problem if its that much of a dog, unless the engine is very tired. BTW, to the board! __________________ '67 C-30 Dually Pickup 6.2 Turbo Diesel, NP435 ‘72 C-10 SWB , 350 4bbl, TH350 '69 C-10 SWB , 250 L6, 3 OTT '69 GMC C3500, dump truck, 351 V6, NP435 '84 M1009 CUCV Military Blazer 67 C-30 Turbodiesel build thread http://67-72chevytrucks.com/vboard/s...d.php?t=254096 My trucks http://s226.photobucket.com/albums/d...ediafilter=all Member of the 1-Ton Club!

09-10-2007, 06:03 PM	#3
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 46,818	Re: Do the 3:08's have to go??? my 69 POS parts truck with a smog motor 305/T350C/3.08s would smoke them without hesitation. Sounds like there are other issues, maybe tranny issues. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

09-10-2007, 07:02 PM	#4
Ackattack Senior Member Join Date: Aug 2002 Location: Valley Center KS Posts: 3,525	Re: Do the 3:08's have to go??? Sounds like a tuning problem to me. If it's not, then a good (but possibly pricey) option is 3.73s with a OD tranny. I'm now getting 18.5 mpg out of mine (but it's also fuel injected) __________________ Project Bruiser: 68 Pro-Touring C-10 5.3L / 4L60E Project Ironhide: 97 GMC Crew Cab 4x4 Cummins SOLD: '69 GMC 1/2T SWB TBI'd: Project No Buck Assembly Manual Index Sign up Thread!!! Factory Service Manual Index

09-10-2007, 07:04 PM	#5
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Do the 3:08's have to go??? Red, I think they are right.Either that or you're expecting too much.In the long run you may want to consider a 700R4 for it though.You will need a 3:73 for that.3:08's were the standard gear for auto's so it should run and tow a boat with no problem. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

09-10-2007, 07:31 PM	#6
Bowtie001 Project underway - finally. Join Date: Feb 2007 Location: Greenville, SC Posts: 493	Re: Do the 3:08's have to go??? One more vote for "it's not the gears". My 84 with a 350 and 3.08's and a th-350 got up fairly quickly. Bring it to the dragstrip and do some tuning... mine ran something like 17.10s stock. Timing and carb are the areas to look for... make sure that the butterflies are opening fully, that's surprisingly easy to miss. Also make sure your secondaries are opening. -Brian __________________ 1972 GMC Pre-resto... awaiting allocated funding.

09-10-2007, 09:57 PM	#7
glock35ipsc Next project: 1970 K10 Join Date: Feb 2004 Location: Fort Collins, Colo 80524 Posts: 6,685	Re: Do the 3:08's have to go??? with the rest of these guys. __________________ *Bob* 1970 Chevy K10 LWB "Goldie" 350/TH350 *next project!!* 1981 Chevy C10 LWB 355/TH350 - My son's truck LS SWAP FORUM! Tons of LS swap info here! PLEASE CLICK HERE TO SUPPORT THE GREATEST BOARD ON THE NET! CLICK HERE FOR THE FAQ INDEX by KRUE

09-10-2007, 10:04 PM	#8
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,861	Re: Do the 3:08's have to go??? Get rid of the power robbing TH400.You don`t need it with what you have,anyway. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

09-11-2007, 08:57 AM	#11
Dean Senior Member Join Date: Jan 2000 Location: Cincinnati, Ohio Posts: 1,492	Re: Do the 3:08's have to go??? Just put a 5.14 in my 55 Chevy and that did the trick......lol I could pull stumps if necessary..............

09-11-2007, 09:06 AM	#12
sleepyboy '69 Step Join Date: Mar 2005 Location: Marion, Texas Posts: 722	Re: Do the 3:08's have to go??? I like my 3:08s __________________ It's my truck, and Yes, I CUT the dash, so what??

09-11-2007, 09:56 AM	#13
Putter More Cowbell.... Join Date: Mar 2004 Location: Puckett, MS Posts: 3,569	Re: Do the 3:08's have to go??? 3.08s here as well....Had 3.73s in there, but needed more interstate speeds. Swapped with GMan. I can do a descent scratch from a dead stop. Agree you may have other issues. __________________ *There once was a member from Puckett.....Who ( fill in the blank blank blank* ) bucket**

09-11-2007, 07:39 PM	#14
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Do the 3:08's have to go??? Red 69 C-10, one more for the "it's not your rear end" vote. FYI: I have a 69 with a tired 350ci with quadrajet and 350 trans with 3.07 rear end. Some years ago I pulled an 18' trailer loaded with a full size tractor, bush hog and other equipment for about 100 miles and had absolutely no problem towing. I also have towed other vehicles, trailer full of lumber, etc. with it and haven't had any problems. As others mentioned, it could be carb, tuning, transmission, or engine. At my age I'm not into peeling out for the fun of it, but I've stepped on it on occasion to "blow it out" and it has enough power for me...

09-12-2007, 08:14 AM	#16
Bowtie001 Project underway - finally. Join Date: Feb 2007 Location: Greenville, SC Posts: 493	Re: Do the 3:08's have to go??? I think we've overwhelmed the poor guy. First off, I forgot to welcome you to the site. Secondly, want any help getting to the problem? -Brian __________________ 1972 GMC Pre-resto... awaiting allocated funding.

09-12-2007, 06:35 PM	#19
mnunn454 Registered User Join Date: Dec 2006 Location: Rhode Island Posts: 602	Re: Do the 3:08's have to go??? Maybe a trip to the local chassis dyno is in order. For about $150 (here in RI) they'll tune carb and timing to provide optimal performance for your normal requirements. Without knowing the details, were it me, I'd attack the issue in this order Tuneup (plugs, wires, ignition module, coil, free breathing intake etc) Carb a/f ratio (you want 14.7:1 when cruising and 12.5:1 when mashing on the gas), Timing (run as much advance as you can w/o pinging or hard starting), Exhaust (minimal back pressure, especially the mufflers), Cam design (profile) and adv/retard, Cam health (are the lobes worn off? Are the timing chain/geears worn?) Heads (both flow and compression ratio), Torque converter stall Swap the tranny for a TH350 or TH200 Change the R&P ratio to a 3.42 or 3.73 __________________ 69 C-10 SWB Fleetside 454/TH400 (For Sale) http://67-72chevytrucks.com/vboard/c...ct=1299&cat=12 70 El Camino 454 TH700 29 Model A 4-DR Sedan Deluxe Last edited by mnunn454; 09-12-2007 at 06:38 PM.

09-12-2007, 06:53 PM	#20
corn Registered User Join Date: Dec 2003 Location: here Posts: 5,789	Re: Do the 3:08's have to go??? This winter Im swapping my 3:07's for 3:73's. Its my toy & the gears will make it more fun.



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09-12-2007, 07:28 PM	#21
brianthelion02 Overdrive club Join Date: Sep 2007 Location: apache junction, arizona Posts: 819	Re: Do the 3:08's have to go??? I agree with start with the basics,tune up and all that maybe even a compression check is in order!!!!!And personally i believe a 700r would be good in youre situation!!!700r have a lower 1st gear which is what you need for that bass or jet boat!!!!And the od will sure help with mpg!!!!! I also never saw anything about tire size,assuming youre near stock size tire?Good luck and let us know what ya find!!!!!!! __________________ 1971 c-10 1951 3100 chevy 1970 chevy c-30 Sold! Last edited by brianthelion02; 09-12-2007 at 07:29 PM.

09-15-2007, 08:27 AM	#22
Red 69 C-10 Registered User Join Date: Sep 2006 Location: California Posts: 11	Re: Do the 3:08's have to go??? Gentlemen, want to thank all you for taking time to address my problem. Going to advance the snot out of it till she pings,lean the primaries and see how she runs. Good to hear from all you. Thanks a bunch.....

09-15-2007, 11:11 AM	#23
Bowtie001 Project underway - finally. Join Date: Feb 2007 Location: Greenville, SC Posts: 493	Re: Do the 3:08's have to go??? Do yourself a favor and make sure that the butterflies are open all the way under WOT. This is surprising, but it makes a BIG difference obviously. __________________ 1972 GMC Pre-resto... awaiting allocated funding.

09-15-2007, 11:23 AM	#24
Robznob11 Registered User Join Date: Feb 2004 Location: brownfield texas (west texas) Posts: 1,936	Re: Do the 3:08's have to go??? well i had a chevy 6 cylinder that lost all its get up and go and found out that i neeeded to change the advance kit, you can get a performance advance kit from auto zone,napa,etc(@$15) looks like two little dog legs and a bunch of different springs they go under the distributor cap, start with the lightest ones and if it pings go to the med, lighter the spring the more advance. when i changed mine they visualy looked great but the car got so bad it would bog itself going up a hill, after i swaped them out i could light up two 8 in tires with a tired 200 v6 __________________ The Ghost 67 short wide full custom. 550 hp LSX, 4l80E, narrowed 9". Body dropped w/air ride! ........................ ___ .........________//__{\_____ ,,,,,,,/__(⊙)___//___/__(O)_/ @disciple2.rc 💪instagram💪 LED TAILS Last edited by Robznob11; 09-15-2007 at 11:24 AM.

09-15-2007, 12:47 PM	#25
Jcentsr6 Junior Member Join Date: Jul 2007 Location: Odenton, Md Posts: 552	Re: Do the 3:08's have to go??? welcome....and check your carb. __________________ going to sell this one...looking for a SWB project next.

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