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67 chevy pickup, can't put on interstate

2K views 11 replies 9 participants last post by  Deuce 
#1 ·
I know nothing about rearends and trans. Old pickup runs very high rpm's on interstate. Has 4 spd trans, 1st gear granny. would like to change transmission without messing with rearend. suggestions?

[ February 23, 2003: Message edited by: chrisf67 ]

[ February 23, 2003: Message edited by: chrisf67 ]</p>
 
#4 ·
Originally posted by chrisf67:
<strong>I know nothing about rearends and trans. Old pickup runs very high rpm's on interstate. Has 4 spd trans, 1st gear granny. would like to change transmission without messing with rearend. suggestions?

[ February 23, 2003: Message edited by: chrisf67 ]

[ February 23, 2003: Message edited by: chrisf67 ]</strong><hr></blockquote>

Unless you go to an overdrive trans, changing the trans will not change your RPM's when driving on the freeway. The high RPM's you are seeing at the present time are because of the rearend ratio. Change your rear gears to a higher ratio (lower numerically) to decrease your cruising RPM's.
 
#5 ·
I would think the title of the post points to a chevy truck of the year 1967. :D

In the days these trucks were new a person could drive them on the freeways. So I wonder what is the real problem here if there is one?

It was common to have 3.73 or 4.10 gears in the trucks of these years.

As pointed out a 700R4 tranny would lower the RPM at freeway speeds.
 
#8 ·
I swapped out my 3:73 rear gears for a set of 3:08`s. I run a 350/350 and it works fine for me. I got the intire rear end from a you pull it for $120.00.
Slider in Wa.
 
#9 ·
Changing your ring gear would help, but those trucks have total granny gear trans ratios. Those 4 speeds are to pull, so they utilize the engines torque. Changing your tranny is what I would do. A 4 speed out of a chevelle or camaro, some sports car is the way to do it. I don’t know what motor you have, but if it’s a Chevy, which it is, then there are tons of transmissions that will fit in you truck. Or you could go to an automatic. Then the 700r4 is the only 4-speed transmission that isn’t computer controlled that I would use. You will have to change your transmission mounts if you change to an automatic. I don’t know for sure about the manual swap. Keep posting to tell us what you have decided.
Silver
 
#11 ·
MUNCIE (SM) 465
Type: 4-spd. manual
Length (in.): 12
Ratios: 6.54:1 (1st)
3.57:1 (2nd)
1.57:1 (3rd)
1.00:1 (4th).
Used by: 1968-1990 Heavy Duty. Chevrolet, in Blazers and pickups

MUNCIE (SM) 420
Type: 4-spd. manual
Length (in.): 10.43
Ratios: 7.05:1 (1st)
3.57:1 (2nd)
1.70:1 (3rd)
1.00:1 (4th).
Used by: 1947-1967 G.M. trucks. HEAVY Duty.
 
#12 ·
Originally posted by chrisf67:
<strong>do you have any idea what my 4th gear ratio is?</strong><hr></blockquote>

High gear is 1 to 1 in all transmissions unless equipped with overdrive. People drove these trucks on the Interstates years ago before everyone got used to overdrive equipped vechicles. I drive a 40 Ford with a 3.78 rear end anywhere I want. To Daytona (375 miles) or Louisville KY (575 miles). My 283 turns 3000 RPMS at 70 MPH. I get 16 MPG at 70 MPH.

You can purchase a lot of fuel for the price of a rear end or transmission. Then your speedometer will be incorrect and have to fix/change that.



:D
 
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