Jump to content

Recommended Posts

How can I determine the rear axle ratio for my B75?

 

ron

Share this post


Link to post
Share on other sites
15 hours ago, Hobert62 said:

Jack it up, put it in neutral, turn the tire, and count the revolutions of the driveshaft for 1 revolution of the tire.  It will get you an idea if you accurately make the yoke and wheel before you start turning.  

Make sure the other side stays on the ground or it will spin and throw off your count.

  • Like 1

Share this post


Link to post
Share on other sites

For the correct count you need wheels at the both sides to turn together. If you have one on the ground (locked from turning) you count must be divided by 2 since the only wheel is forsed to make 2 times more revs by differential.

  • Like 1

Share this post


Link to post
Share on other sites

Worth to add. The most accurate count of the reatio is count of actual number of the teeth. But complete carrier remove could be required. Talking about Mack tandem carriers you can count the teeth of the upper (bewel) set of gears through the side cover opened but not the lower (bull) ones.

Share this post


Link to post
Share on other sites
5 hours ago, Vladislav said:

For the correct count you need wheels at the both sides to turn together. If you have one on the ground (locked from turning) you count must be divided by 2 since the only wheel is forsed to make 2 times more revs by differential.

You're right, divide by 2. When I have both wheels off the ground, the opposite wheel usually spins backwards, throwing off the ratio count.

  • Like 1

Share this post


Link to post
Share on other sites

Kind of hard to do with two rear axles.  I'll chk for the stamp.

Share this post


Link to post
Share on other sites
4 minutes ago, 1wonton said:

Kind of hard to do with two rear axles.  I'll chk for the stamp.

See the bottom picture for the location of the stamp.

Unit Identification.jpg

Share this post


Link to post
Share on other sites

Thank you j, this was helpful.  I found the numbers are depicted in the tech sheet but it doesn't tell me much.  The carrier says CRDP 92.161.66, what does this mean?

 

 

ron

Share this post


Link to post
Share on other sites
1 hour ago, 1wonton said:

Thank you j, this was helpful.  I found the numbers are depicted in the tech sheet but it doesn't tell me much.  The carrier says CRDP 92.161.66, what does this mean?

 

 

ron

It should be right next to the stuff you found, sometimes stamped, or numbers made by a center punch, sometimes real light.     terry:MackLogo:

Share this post


Link to post
Share on other sites

Look more over that square spot on the carrier front. Usually at the right side at the the bottom are numbers indicating the ratio. They're standing apart from the rest. Something like 5.02 or 4.46 or 5.73 etc.

  • Like 1

Share this post


Link to post
Share on other sites

Found r 6.34 on real bogie;  does this mean the ratio is 6.34?

Share this post


Link to post
Share on other sites
1 hour ago, 1wonton said:

Found r 6.34 on real bogie;  does this mean the ratio is 6.34?

I would say yes, for that year of truck.  terry:MackLogo:

  • Like 1

Share this post


Link to post
Share on other sites

OK, thanks gentlemen.  I'm about maxed out at 55 and 2000 rpms.  Can't keep up with the big boys but I catch them in the mountains.

Share this post


Link to post
Share on other sites

Ya, back when power was low, gearing was slow.

What transmission?  If it is single OD, then 55 is likely about it.  My B had 4.62's and would go 65 mph flat out.  A double over would get you closer to 65 mph.

Share this post


Link to post
Share on other sites

OK, thanks gentlemen.  I'm about maxed out at 55 and 2000 rpms.  Can't keep up with the big boys but I catch them in the mountains.

 

 

Single od, quadraplex.  Emd 673 turbo.

Share this post


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
Reply to this topic...

×   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.


×
×
  • Create New...