The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 05-03-2015, 09:19 PM   #1
1979-square-body
Registered User
 
1979-square-body's Avatar
 
Join Date: Apr 2015
Location: N/a
Posts: 71
No good on the freeway

Drove home the 79 today. 350 motor and trans, flow master exhaust. Speedo works but it is off. She wasn't screaming, but she also wasn't hauling ass.

No overdrive and have no idea what rear end gears she has.

Any ideas to make the top end a bit better? Or where to start?
1979-square-body is offline   Reply With Quote
Old 05-03-2015, 11:01 PM   #2
farmall
Registered User
 
farmall's Avatar
 
Join Date: Jun 2011
Location: Central OR
Posts: 728
Re: No good on the freeway

Gearing, taller tires, overdrive.
__________________
1955 GMC 250 8 Flatbed
1971 C30 157" 350 4spd 10' Flatbed
81 GMC K30 CnC 9' Flatbed 454 T400
89 GMC Jimmy Stock https://67-72chevytrucks.com/vboard/...d.php?t=810958
71 LT1 Convertible, 72 Coupe
69 CJ5, 75 CJ6, 67 M715, 72 M35A2 Bobbed, 95 XLC2
farmall is offline   Reply With Quote
Old 05-03-2015, 11:44 PM   #3
1979-square-body
Registered User
 
1979-square-body's Avatar
 
Join Date: Apr 2015
Location: N/a
Posts: 71
Re: No good on the freeway

Can I add a shift kit in the trans to get an OD?
1979-square-body is offline   Reply With Quote
Old 05-04-2015, 04:25 AM   #4
donut
Registered User
 
donut's Avatar
 
Join Date: Aug 2009
Location: S.C.
Posts: 1,593
Re: No good on the freeway

No, shift kit will firm up what you have provided it's in decent shape.
__________________
'86 C-30 dually, 454/tbh400
'73 K-20 350/350/205 (sold )

I'm kinda like duct tape- no real purpose, but handy to have around.
donut is offline   Reply With Quote
Old 05-04-2015, 11:34 AM   #5
Bigstevex4
Registered User
 
Bigstevex4's Avatar
 
Join Date: Oct 2014
Location: Spearfish South Dakota
Posts: 407
Re: No good on the freeway

The speed Limit was 55 when it was built. Tall tires are the cheapest way limited to how much say 300 rpm rear gears are next gears even 4 wheel drive you could cut rpm by a 1000 depending were its at now . Over drive trans and or overdrive unit cut them 25 % But cost is higher considerably higher. if your not a fair mechanic. Or and this is me it is what it is any time you swap things around it always cost way more than you figured. Just live with it unless your planning on putting a 100 miles a day on it.
__________________
83 c10 long Box Daily Driver
90 Jimmy parked
98 Road King/ 06 Road Glide
In memorium
63 impala SS/ 65 Chevy Panel
65 GMC Short Box/ 68 Camero
Bigstevex4 is offline   Reply With Quote
Old 05-04-2015, 11:42 AM   #6
Keith Seymore
Registered User
 
Keith Seymore's Avatar
 
Join Date: May 2009
Location: Motor City
Posts: 9,226
Re: No good on the freeway

Quote:
Originally Posted by 1979-square-body View Post
Drove home the 79 today. 350 motor and trans, flow master exhaust. Speedo works but it is off. She wasn't screaming, but she also wasn't hauling ass.

No overdrive and have no idea what rear end gears she has.

Any ideas to make the top end a bit better? Or where to start?
Start by figuring out what rear gears you have.

This would be an excellent time to pull the cover, replace the gear lube in the rear axle and count teeth on the ring and pinion.

Report back and we can make further recommendations from there. Bigsteve's questions about usage and number of miles you will be driving are relevant and should be addressed.

K
__________________
Chevrolet Flint Assembly
1979-1986
GM Full Size Truck Engineering
1986 - 2019
Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926
My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524
Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/
Keith Seymore is offline   Reply With Quote
Old 05-04-2015, 01:33 PM   #7
Dead Parrot
Registered User
 
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 2,611
Re: No good on the freeway

If you have a hand held GPS, most have a speedometer function. You can find out how off and which way off your speedometer is.

Does it have the original y-pipe? My 75 came with a double wall y. When the inner wall collapsed, it really screwed up the top end.
Dead Parrot is offline   Reply With Quote
Old 05-04-2015, 04:28 PM   #8
RIDE-RED 350r
Registered User
 
RIDE-RED 350r's Avatar
 
Join Date: Mar 2014
Location: Blossvale NY
Posts: 202
Re: No good on the freeway

Or if you have a smartphone, there are dozens of free GPS speedometer apps. And they seem to be quite accurate.

Can't disagree with any previous recommendations.
__________________
Who needs a Hemi when ya got a Chevy!
RIDE-RED 350r is offline   Reply With Quote
Old 05-04-2015, 11:52 PM   #9
1979-square-body
Registered User
 
1979-square-body's Avatar
 
Join Date: Apr 2015
Location: N/a
Posts: 71
Re: No good on the freeway

It seems there a few other things that need to be done prior to rear axle upgrades. Took her for a spin today, started to misfire during acceleration. I looked around a little more and saw the passenger side muffler is sagging way further down than the driver side. Also it's all hung up there with bailing wire. The Painless wiring loom need to be finished up (none of the interior lights work and all the other gauges besides speedo aren't hooked up), windows and doors need new weather seals and there are a few other things too.

Need to get her road ready before I do anything else...
1979-square-body is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 09:37 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com