New guy question on a 77 F 150 - Ford F150 Forum - Community of Ford Truck Fans

Topic Sponsor
Pre- 1987 / Classic Corner Have a classic Ford F150 truck? Want a classic? Discuss your pre-1987 Ford F150 truck.

New guy question on a 77 F 150

 
Old 10-22-2018, 05:30 PM
  #1  
Junior Member
Thread Starter
 
Join Date: Oct 2018
Location: Bemidji Mn.
Posts: 6
Thanked 0 Times in 0 Posts
Default New guy question on a 77 F 150

Ive got a 77 F 150 4x4 with a 400 and 4 speed, the problem I;m having is the rpm;s going down the road at 60 mph are screaming(I don't have a tach.). There is no tag on the rear end to check gear ratio so I spun the driveshaft and counted tire rotations, the gearing seems to be 411. My question is what can I do to get the rpms down, is there a 5 speed or overdrive that would bolt up or am I going to need to change the diff. gears. I;m going with 35 inch tires and the truck is just a toy not an every day driver..Thanks...
don62 is offline  
Old 10-22-2018, 05:47 PM
  #2  
Senior Member
 
Join Date: Sep 2017
Location: Near Macomb, Illinois
Posts: 628
Thanked 118 Times in 80 Posts
Default

If you have that kind of gearing not much you can do about it other than swap out the gears. There are various over drive setups but I doubt you can find one for that truck. There might be a transmission that's a direct swap that has an over drive but I'm not sure. The problem is also you can't just swap the rear gears but you have to do the front also.
dodgeman1 is offline  
Old 10-22-2018, 09:38 PM
  #3  
Junior Member
Thread Starter
 
Join Date: Oct 2018
Location: Bemidji Mn.
Posts: 6
Thanked 0 Times in 0 Posts
Default

Yea, I know I have to do front and rear, I was hoping someone here might have an easier fix. Is it hard to do the front diff. or about the same as rear??
don62 is offline  
Old 10-22-2018, 09:55 PM
  #4  
Senior Member
 
Join Date: Jan 2016
Posts: 457
Thanks: 0
Thanked 59 Times in 40 Posts
Default

Do you have the 35s in yet or what size currently? Bigger tires will lower the rpm a little. My jep is running 4.88 on 33s, rpms at 65 mph AR about 2800. It's a toy also so I haven't bothered to change gears or tires. Gearing will take some time and special tools. That's why install prices are so high, you don't just swap out the ring and pinion in one shot.
Brokemillwright is offline  
Old 10-22-2018, 10:13 PM
  #5  
Junior Member
Thread Starter
 
Join Date: Oct 2018
Location: Bemidji Mn.
Posts: 6
Thanked 0 Times in 0 Posts
Default

No, don't have the 35s on, tires on it now measure 28 inchs tall, I know the taller tires will make a difference, I just don't think it will make the difference I'm looking for.
don62 is offline  
Old 10-23-2018, 04:11 PM
  #6  
Senior Member
 
Join Date: Sep 2017
Location: Near Macomb, Illinois
Posts: 628
Thanked 118 Times in 80 Posts
Default

I know for classic cars they make 4 speeds where 4th gear is an overdrive and better yet 5 speeds where 5th gear is an over drive. Most of these are meant for cars but maybe they have one that would bolt up to your truck?
dodgeman1 is offline  
Old 10-23-2018, 04:51 PM
  #7  
Senior Member
 
KingDeleted's Avatar
 
Join Date: Apr 2018
Posts: 370
Thanked 57 Times in 39 Posts
Default

Originally Posted by don62 View Post
No, don't have the 35s on, tires on it now measure 28 inchs tall, I know the taller tires will make a difference, I just don't think it will make the difference I'm looking for.
going from 28s to 35s will make quite a bit of difference. Assuming you have 4.11 now the 35s will make it feel like you have 3.31. Id do the tires and then see if it needs anything after that.
KingDeleted is offline  
Old 10-23-2018, 10:08 PM
  #8  
Senior Member
 
Join Date: Jan 2016
Posts: 457
Thanks: 0
Thanked 59 Times in 40 Posts
Default

28" to 35" will make a noticeable difference. I don't feal like doing the work for you, so figure out what tranny you have, plug the info in currently then compare to 35s. Math never lies http://www.grimmjeeper.com/gears.html

edit:I lied and got curiouse. Np435 close ratio, no tcase since I read they don't have low range, 4.11 gears.

28\"

35\"

Last edited by Brokemillwright; 10-23-2018 at 10:27 PM.
Brokemillwright is offline  
The Following User Says Thank You to Brokemillwright For This Useful Post:
don62 (10-24-2018)
Old 10-24-2018, 01:29 AM
  #9  
Junior Member
Thread Starter
 
Join Date: Oct 2018
Location: Bemidji Mn.
Posts: 6
Thanked 0 Times in 0 Posts
Default

Thanks for doing the work, I guess I will try the tires first, I;m gonna get them anyway so why not...
don62 is offline  
Old 10-25-2018, 01:44 AM
  #10  
Junior Member
Thread Starter
 
Join Date: Oct 2018
Location: Bemidji Mn.
Posts: 6
Thanked 0 Times in 0 Posts
Default

I'm getting mixed opinions, will 35s on 15x10 inch rims fit without a lift? some say yes some say no, has anyone used them?
don62 is offline  

Thread Tools
Search this Thread
Quick Reply: New guy question on a 77 F 150


Contact Us Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: