Need a little help. 2 questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Baggerjohn · 03-06-2011, 11:53 AM

I have a 67 lwb 2wd C-10 with a 250 inline 6 with a 5 speed trans. I don't know what rear end gears I have. I am getting really bad gas mileage. I do not have a speedometer. I have the one barrel carb. I had hoped for better mileage. I do have a tach that shows when I'm going approx. 65 mph the tach is at 1200 rpm. Think the tach is wrong. Any help would be great.
Question #2 is the bench seat my truck came with is touching the doors when closed and it is uncomfortable. I bought another seat that I think is the right length but when installed sits real low. How can I safely raise the seat so that I see where I'm going?
Since retiring my wife thought I needed something to occupy my time I chose this truck. Just need a little advice please. Thanks.

oldblue1968chevy · 03-06-2011, 12:24 PM

Wow! Thats low rpms!

Try another tach?

Have you changed diff. oil lately? Go to the store and get a gasket for your rearend (most likely 12 bolt) and some gear oil, note the #'s stamped on ring gear (big gear) divide little into big number, that'll give you your ratio.

dmack91 · 03-06-2011, 01:09 PM

5 speed? Wonder what it came out of.

As far as the seat goes, in the past I have lifted them with square steel tubing between the floor and the mounting rails. Just take the stock bolts out and shim up with wood scraps until you get the height you want. Measure what you have and get some square steel tube of that size. Just drill corresponding holes and get longer bolts and you are ready to go.

basemodel67 · 03-06-2011, 01:17 PM

First step: make sure tach is for a 6 cylinder!!!

Getting taller tires could help too. As far as seat problem, get a piece of square tubing and drill two holes in it and put it under the seat stands - cheap and easy!

Or what he said ^^^^

PanelDeland · 03-06-2011, 02:09 PM

Or you can jack up the rear wheels and turn one one full turn.Put a chalk mark on the driveshaft and see how many times it rotates while turning the wheel.Though not 100% acurate you will get a good idea of what ration you have.The tranny will need to be in nuetral.
Typical rear ratios are 3.73:1 4.11:1 4.53:1 for standards
3.07-08:1 for auto.

68gmsee · 03-06-2011, 03:49 PM

You could also clean the top of the axle passenger side real good and see if you have some numbers stamped on top then post them here or look on GMC Pauls site. Years of grime accumulation make them almost invisible. I had to wire brush mine.

If you want to keep from getting a ticket and to see how fast you are going go buy a gps unit like a Garmin. I used mine to when my speedometer went belly up on another vehicle. Worked great and pretty accurate.

fyi: these old trucks don't get very good mileage. There are some that can squeeze upwards of 18 mpg but from my experience 15 or less on the highway is the norm.

Jacfourteen · 03-06-2011, 04:00 PM

All of these are good suggestions, if the speedo isn't working you might want to check the cable. I checked mine by reaching up under the dash to unscrew it then took a drive and watched to see if it spun when moving, mine didn't so I changed it out (not spinning could also mean stripped speedo gear in the tailshaft). When mine went out I replaced it I think it cost about $13 and took about a half an hour to replace.

Longhorn Man · 03-06-2011, 04:02 PM

how bad is your MPG?
How do you know with no speedo?
Whats the RPMs in 4th gear?

I'm willing to bet a kick in the balls that someone put a 3.07 rear in there and with the 5 speed it puts the RPMs too low and the engine is working hard (lugging) at that stupid low RPM.

Jacfourteen · 03-06-2011, 04:16 PM

Quote:

Originally Posted by Longhorn Man

how bad is your MPG?
How do you know with no speedo?
Whats the RPMs in 4th gear?

I'm willing to bet a kick in the balls that someone put a 3.07 rear in there and with the 5 speed it puts the RPMs too low and the engine is working hard (lugging) at that stupid low RPM.

I was thinking all the same things. I say fix speedo, then recalculate MPG to see where you stand. A good carb cleaning/tuning, new air filter, plugs and wires couldn't hurt either.

Baggerjohn · 03-07-2011, 03:13 PM

Quote:

Originally Posted by dmack91

5 speed? Wonder what it came out of.

As far as the seat goes, in the past I have lifted them with square steel tubing between the floor and the mounting rails. Just take the stock bolts out and shim up with wood scraps until you get the height you want. Measure what you have and get some square steel tube of that size. Just drill corresponding holes and get longer bolts and you are ready to go.

dmack 91, don't know where the trans came from. Like it though.Thanks for the info on how to raise the seat. Will do as soon as I can find a supplier for the metal. Thanks again.

Baggerjohn · 03-07-2011, 03:17 PM

Quote:

Originally Posted by PanelDeland

Or you can jack up the rear wheels and turn one one full turn.Put a chalk mark on the driveshaft and see how many times it rotates while turning the wheel.Though not 100% acurate you will get a good idea of what ration you have.The tranny will need to be in nuetral.
Typical rear ratios are 3.73:1 4.11:1 4.53:1 for standards
3.07-08:1 for auto.

PanelDeland, thanks for the info on how to find gear ratio. I will try it. Thanks again.

John

**Zeke's Garage** · 03-07-2011, 03:27 PM

A little better way to check the rear ratio is to put the rear up on jack-stands and put a piece of tape on the bottom of both tires and the drive shaft. Then rotate the drive shaft and count the turns until both tires rotate once. The tape ensures that both rear tires move the same amount and isn't working the spider gears in the diff, throwing off your measurement.

Like Longhorn Man says, you'll probably get just over 3 turns of the drive shaft for one rotation of the tires, roughly 3.07:1 ratio.

If all the above rings true, just keep it in 4th gear, and you'll probably see a little better mileage and drive-ability out of it.

dmack91 · 03-08-2011, 12:02 AM

Quote:

Originally Posted by Baggerjohn

dmack 91, don't know where the trans came from. Like it though.Thanks for the info on how to raise the seat. Will do as soon as I can find a supplier for the metal. Thanks again.

Most steel yards have a scrap section with misc. small sections for sale by the pound (about 45 cents a pound here). Might also check with some local welding/repair shops. They may have some scraps you can buy cheap (or cut some to size for you).

Jacfourteen · 03-08-2011, 02:59 AM

post up some pics and I'm sure someone can ID the tranny for you.

03-06-2011, 11:53 AM	#1
Baggerjohn Registered User Join Date: Jan 2011 Location: Bullhead City, AZ Posts: 60	Need a little help. 2 questions I have a 67 lwb 2wd C-10 with a 250 inline 6 with a 5 speed trans. I don't know what rear end gears I have. I am getting really bad gas mileage. I do not have a speedometer. I have the one barrel carb. I had hoped for better mileage. I do have a tach that shows when I'm going approx. 65 mph the tach is at 1200 rpm. Think the tach is wrong. Any help would be great. Question #2 is the bench seat my truck came with is touching the doors when closed and it is uncomfortable. I bought another seat that I think is the right length but when installed sits real low. How can I safely raise the seat so that I see where I'm going? Since retiring my wife thought I needed something to occupy my time I chose this truck. Just need a little advice please. Thanks. __________________ "Arrive, Raise Hell, Create Confusion, Leave".

03-06-2011, 01:09 PM	#3
dmack91 Registered User Join Date: Jan 2011 Location: Redmond, OR Posts: 755	Re: Need a little help. 2 questions 5 speed? Wonder what it came out of. As far as the seat goes, in the past I have lifted them with square steel tubing between the floor and the mounting rails. Just take the stock bolts out and shim up with wood scraps until you get the height you want. Measure what you have and get some square steel tube of that size. Just drill corresponding holes and get longer bolts and you are ready to go. __________________ 68 Chev C20- son has it now 83 K20 - bought from son 70 C20 - in progress

03-06-2011, 01:17 PM	#4
basemodel67 Factory Strippers Rule! Join Date: Mar 2009 Location: Shingle Springs, CA Posts: 707	Re: Need a little help. 2 questions First step: make sure tach is for a 6 cylinder!!! Getting taller tires could help too. As far as seat problem, get a piece of square tubing and drill two holes in it and put it under the seat stands - cheap and easy! Or what he said ^^^^ __________________ "Feast your eyes on a feast of smoke." 67 Chevy Short Fleet PLAN: LQ9, 4L60, D60 Looking for School Bus Gauges - Help me out! Last edited by basemodel67; 03-06-2011 at 01:18 PM.

03-06-2011, 02:09 PM	#5
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Need a little help. 2 questions Or you can jack up the rear wheels and turn one one full turn.Put a chalk mark on the driveshaft and see how many times it rotates while turning the wheel.Though not 100% acurate you will get a good idea of what ration you have.The tranny will need to be in nuetral. Typical rear ratios are 3.73:1 4.11:1 4.53:1 for standards 3.07-08:1 for auto. __________________ 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"

03-06-2011, 03:49 PM	#6
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Need a little help. 2 questions You could also clean the top of the axle passenger side real good and see if you have some numbers stamped on top then post them here or look on GMC Pauls site. Years of grime accumulation make them almost invisible. I had to wire brush mine. If you want to keep from getting a ticket and to see how fast you are going go buy a gps unit like a Garmin. I used mine to when my speedometer went belly up on another vehicle. Worked great and pretty accurate. fyi: these old trucks don't get very good mileage. There are some that can squeeze upwards of 18 mpg but from my experience 15 or less on the highway is the norm.

03-06-2011, 12:24 PM	#2
oldblue1968chevy Grandpa in the rustmobile... Join Date: Nov 2008 Location: Spokane WA/Viola TN Posts: 11,422	Re: Need a little help. 2 questions Wow! Thats low rpms! Try another tach? Have you changed diff. oil lately? Go to the store and get a gasket for your rearend (most likely 12 bolt) and some gear oil, note the #'s stamped on ring gear (big gear) divide little into big number, that'll give you your ratio. __________________ John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4

03-06-2011, 04:00 PM	#7
Jacfourteen Big Red - Now its a SWB! Join Date: Jun 2009 Location: Oroville, Ca Posts: 1,624	Re: Need a little help. 2 questions All of these are good suggestions, if the speedo isn't working you might want to check the cable. I checked mine by reaching up under the dash to unscrew it then took a drive and watched to see if it spun when moving, mine didn't so I changed it out (not spinning could also mean stripped speedo gear in the tailshaft). When mine went out I replaced it I think it cost about $13 and took about a half an hour to replace. __________________ 68 3/4 ton (Project)-350 Small Block, .030 over, 10:1 comp, 3998993 heads, C3BX edelbrock intake, comp cams XE268, Holley 670 SA, long tube headers, dual flow 40's, E-fan, Alum rad, currently under the knife getting shortened and bagged build thread 41 3/4 ton (wife's)-flatbed, fully restored to original 01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's

03-06-2011, 04:02 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Need a little help. 2 questions how bad is your MPG? How do you know with no speedo? Whats the RPMs in 4th gear? I'm willing to bet a kick in the balls that someone put a 3.07 rear in there and with the 5 speed it puts the RPMs too low and the engine is working hard (lugging) at that stupid low RPM.

03-07-2011, 03:27 PM	#12
Zeke's Garage Senior Member Join Date: Feb 2010 Location: Kennesaw, GA Posts: 288	Re: Need a little help. 2 questions A little better way to check the rear ratio is to put the rear up on jack-stands and put a piece of tape on the bottom of both tires and the drive shaft. Then rotate the drive shaft and count the turns until both tires rotate once. The tape ensures that both rear tires move the same amount and isn't working the spider gears in the diff, throwing off your measurement. Like Longhorn Man says, you'll probably get just over 3 turns of the drive shaft for one rotation of the tires, roughly 3.07:1 ratio. If all the above rings true, just keep it in 4th gear, and you'll probably see a little better mileage and drive-ability out of it.

03-08-2011, 02:59 AM	#14
Jacfourteen Big Red - Now its a SWB! Join Date: Jun 2009 Location: Oroville, Ca Posts: 1,624	Re: Need a little help. 2 questions post up some pics and I'm sure someone can ID the tranny for you. __________________ 68 3/4 ton (Project)-350 Small Block, .030 over, 10:1 comp, 3998993 heads, C3BX edelbrock intake, comp cams XE268, Holley 670 SA, long tube headers, dual flow 40's, E-fan, Alum rad, currently under the knife getting shortened and bagged build thread 41 3/4 ton (wife's)-flatbed, fully restored to original 01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's



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