I need opinions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

greasemonkey · 01-26-2003, 12:51 PM

My truck has the stock 4-speed manual and 3.07 rear gears, which is fine for in-town driving, but on freeways from 60-70mph the engine sounds like it is about to explode (I haven't driven it above that). Eventually I will rebuild the engine to a very mild performance, but the truck will still be a daily driver. I have the stock 15" rims on it with 235/75 tires. I would like to put new rims and tires on it as the front tires are getting very worn. Would you guys suggest putting bigger rims on it, like 16/17", to get better mileage with my trans and gears? I intend to drop it maybe 1"/3" or just a small drop nothing radical. I like the Eagle rims, but the ones I like come in 14-16". And the tires I like are Radial T/As. Anyway, what tire/wheel combo would you recommend to someone wanting better mileage and a good-looking tire package? Thanks
John

crazy longhorn · 01-26-2003, 01:00 PM

Your 3.07 gears should keep the rpms down on the hyway, & shouldnt be bad at all with a 235/75/15 tire. A set of 3.73s tend to buzz the eng a little on the hyway. My 4.10s , on a 28" tall tire spin the eng 3000 rpms @ 60mph. Do you have a tach to check rpms @ hyway speed? Here is a calculator you can play with on speed/rpm..... http://www.smokemup.com/auto_math/mph_range.php

dion · 01-26-2003, 01:24 PM

Your RPM's should be low with 3.07 at 60

greasemonkey · 01-26-2003, 02:04 PM

I don't have a tach in the truck, I am going by engine sound... Come to think of it, I haven't actually ever checked the gear ratio, but I was under the impression that 4-spd came with 3.07? I guess it's time to pop the cover, the fluid probably needs changing anyway. If they are 3.07, I could go with my original plan. Thanks guys.

Longhorn Man · 01-26-2003, 05:31 PM

Here is what a 3.07 geared truck with an automatic tranny and 275/60R15's spins on the freeway.

Since yours is a stick and should have no slipping, you can drop that RPM down a couple hundred.
If you went with bigger rims, you'd have a hard time finding tall tires since all the 16, 17 and 18 inch tires are for the pro touring look. You caould get tall 16's, but they are truck rims and not intended for the 16's you are refering too...only the 6 and 8 lug truck wheels.
If 2200 RPM is too much for you, you'll need either some real tall 15 inch tires, an overdrive tranny, or a gear chainge in the rear to something like a 2.73, which I am unsuree if they make them for this rear...a 3.07 was as tall as you could get stock.
looking in my book, you are correct in thinkng that 3.07 gears are stock with a 4 speed in 69.

crazy longhorn · 01-26-2003, 05:43 PM

Thats runnin nice & easy there Longhorn!

Fred T · 01-26-2003, 06:58 PM

If it's the granny box 4 speed (SM465) I would bet it has 4.10 gears. If that's the case I would find a 3.07 rear.

greasemonkey · 01-26-2003, 07:58 PM

It is the granny 4 speed.... 2200 RPM wouldn't be bad at all, but my engine sounds much higher than that to the ear, but it is an old tired 350 and could be ready to go. Thanks everybody

Longhorn Man · 01-27-2003, 12:42 AM

in the 1/2 ton, only way to get a 4.11 was with an OD tranny.

Snowbound · 01-27-2003, 01:59 AM

I'm willing to bet you have a 3.73 rear in there. It should say on your option sheet if you still have it. If you jack the back end up and mark the drive shaft with a grease pencil and spin the wheel by hand you can figure out the ratio. It should take 3.73 revs of the wheel to make one turn of the driveshaft.

Or pop the cover like you said. There will be a number stamped on the ring gear like 41:11. Divide the large number by the small number to get your ratio. 41/11=3.73

Have fun,

Brian

01-26-2003, 12:51 PM	#1
greasemonkey Registered User Join Date: Dec 2001 Location: Pace, FL Posts: 2,155	I need opinions My truck has the stock 4-speed manual and 3.07 rear gears, which is fine for in-town driving, but on freeways from 60-70mph the engine sounds like it is about to explode (I haven't driven it above that). Eventually I will rebuild the engine to a very mild performance, but the truck will still be a daily driver. I have the stock 15" rims on it with 235/75 tires. I would like to put new rims and tires on it as the front tires are getting very worn. Would you guys suggest putting bigger rims on it, like 16/17", to get better mileage with my trans and gears? I intend to drop it maybe 1"/3" or just a small drop nothing radical. I like the Eagle rims, but the ones I like come in 14-16". And the tires I like are Radial T/As. Anyway, what tire/wheel combo would you recommend to someone wanting better mileage and a good-looking tire package? Thanks John __________________ 1942 Master Deluxe 1969 C/10 1985 Blazer CUCV 1987 Jimmy 2004 Tahoe 2005 Silverado 1500 2005 Silverado 3500

01-26-2003, 01:00 PM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Your 3.07 gears should keep the rpms down on the hyway, & shouldnt be bad at all with a 235/75/15 tire. A set of 3.73s tend to buzz the eng a little on the hyway. My 4.10s , on a 28" tall tire spin the eng 3000 rpms @ 60mph. Do you have a tach to check rpms @ hyway speed? Here is a calculator you can play with on speed/rpm..... http://www.smokemup.com/auto_math/mph_range.php __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... Last edited by crazy longhorn; 01-26-2003 at 01:09 PM.

01-26-2003, 01:24 PM	#3
dion 72 Cheyenne Join Date: Oct 2001 Location: San Diego Posts: 2,086	What he said Your RPM's should be low with 3.07 at 60 __________________ Burnout Idle 1972Cheyenne 1966/67Stouts

01-26-2003, 02:04 PM	#4
greasemonkey Registered User Join Date: Dec 2001 Location: Pace, FL Posts: 2,155	I don't have a tach in the truck, I am going by engine sound... Come to think of it, I haven't actually ever checked the gear ratio, but I was under the impression that 4-spd came with 3.07? I guess it's time to pop the cover, the fluid probably needs changing anyway. If they are 3.07, I could go with my original plan. Thanks guys. __________________ 1942 Master Deluxe 1969 C/10 1985 Blazer CUCV 1987 Jimmy 2004 Tahoe 2005 Silverado 1500 2005 Silverado 3500

01-26-2003, 05:43 PM	#6
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Thats runnin nice & easy there Longhorn! __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

01-26-2003, 05:31 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Here is what a 3.07 geared truck with an automatic tranny and 275/60R15's spins on the freeway. Since yours is a stick and should have no slipping, you can drop that RPM down a couple hundred. If you went with bigger rims, you'd have a hard time finding tall tires since all the 16, 17 and 18 inch tires are for the pro touring look. You caould get tall 16's, but they are truck rims and not intended for the 16's you are refering too...only the 6 and 8 lug truck wheels. If 2200 RPM is too much for you, you'll need either some real tall 15 inch tires, an overdrive tranny, or a gear chainge in the rear to something like a 2.73, which I am unsuree if they make them for this rear...a 3.07 was as tall as you could get stock. looking in my book, you are correct in thinkng that 3.07 gears are stock with a 4 speed in 69.

01-26-2003, 06:58 PM	#7
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	If it's the granny box 4 speed (SM465) I would bet it has 4.10 gears. If that's the case I would find a 3.07 rear. __________________ Fred There is no such thing as too much cam...just not enough engine.

01-26-2003, 07:58 PM	#8
greasemonkey Registered User Join Date: Dec 2001 Location: Pace, FL Posts: 2,155	It is the granny 4 speed.... 2200 RPM wouldn't be bad at all, but my engine sounds much higher than that to the ear, but it is an old tired 350 and could be ready to go. Thanks everybody __________________ 1942 Master Deluxe 1969 C/10 1985 Blazer CUCV 1987 Jimmy 2004 Tahoe 2005 Silverado 1500 2005 Silverado 3500

01-27-2003, 12:42 AM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	in the 1/2 ton, only way to get a 4.11 was with an OD tranny.

01-27-2003, 01:59 AM	#10
Snowbound Registered User Join Date: Aug 2002 Location: Westbank, BC Posts: 403	I'm willing to bet you have a 3.73 rear in there. It should say on your option sheet if you still have it. If you jack the back end up and mark the drive shaft with a grease pencil and spin the wheel by hand you can figure out the ratio. It should take 3.73 revs of the wheel to make one turn of the driveshaft. Or pop the cover like you said. There will be a number stamped on the ring gear like 41:11. Divide the large number by the small number to get your ratio. 41/11=3.73 Have fun, Brian __________________ 1965 Chevy Short Box Stepside, 230 - 3 speed, 4:11 gears, original paint rust free survivor. Now sporting a 383 SBC and TKO-600



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