Jump to content
  • 0

1988 r690 speed ?’s


66rmack

Question

I’m looking at a 88 R-690 tri axle dump it has a em6-300L with a 2070 trans and 5:73 gears. Everything about the truck is perfect for wat I want except the top speed of 59mph. I have another 89 Mack that has 4:42 gears if I put those carriers in would it sacrifice too much power? I don’t mind being under powered but I don’t want it to struggle to go. Or is there another route I could go? I really need it to go 65mph. Could I get away with 24 talls and turning it up to 2400rpm? Thank you all for your help in advance! I know this ? Has been brought up mor than once in here.  Pick for reference. 

F44EBC99-38E0-4A07-8299-06A29C87C0FD.jpeg

Link to post
Share on other sites

4 answers to this question

Recommended Posts

  • 0

So I did some figures and it looks like the 2070 has a final drive of .60 and 41'' tire with 2100rpms off the engine and 5:73 final drive ratio gives it a top speed of 74.53 mph so I guess I need to go drive it. The salesman told me it would go 58 on the flat according to his gps. I am going to go look at it friday afternoon I will report back, Anybody have a rough idea what its worth? Its very solid the bed is beat up no major oil leaks unknown mileage decent tires but getting ready for brakes. 

Link to post
Share on other sites
  • 0

The em6-300L is governed at like 1750 rpms. It won't do 2100 rpms unless you're going down hill. We bought an 88 2 years ago, still assembling a truck body for it so we haven't had it on the road yet to know how it drives.

Link to post
Share on other sites
  • 0

a 300L is a low RPM motor that has a max loaded rpm of 1750. you can pull the pump and have it re-calibrated to 2100 RPM. for a few $100 bills....it will then be a 70+mph truck. and it will drive better than that junk 1750 spec..   you will burn more fuel but it will drive like it should

 

 

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...