Differential Gear Changeout
Posting Guru
Joined: Mar 2005
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From: KY
Since you live near a big town call the truck dealerships. Kenworth, IH, Peterbuilt, Mack , Volvo. Gear work in in heavy trucks is an everyday thing. They will be able to get you in the right direction.
Don't call them if you can get time to go and see them. If you call you may get a service writer that may tell that "we don't work on light duty trucks".
Go in and ask for the service manager or the shop forman and talk to them.
I will check tom. and see if any of my old dealership contacts know anybody out there. They may. I used to see people from dealerships all over the country when I went to certification classes for new products also the MId-America Truck Show is in the city close to my hometown. I have alot of connections but I need to see if they are still around or they left the dealership world like I did so I could have a family life.
I willsee what I can come with.
Don't call them if you can get time to go and see them. If you call you may get a service writer that may tell that "we don't work on light duty trucks".
Go in and ask for the service manager or the shop forman and talk to them.
I will check tom. and see if any of my old dealership contacts know anybody out there. They may. I used to see people from dealerships all over the country when I went to certification classes for new products also the MId-America Truck Show is in the city close to my hometown. I have alot of connections but I need to see if they are still around or they left the dealership world like I did so I could have a family life.
I willsee what I can come with.
Senior User
Joined: Dec 2003
Posts: 221
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From: Grosse Ile Mi.
Jack up one wheel have someone crawl under the truck and count how many driveshaft turns you get... turn the wheel 20 rev...and you will get a number like 46.3 or 41.0 move the decimile point one to the left...and you will have it
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Junior User
Joined: Sep 2006
Posts: 61
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From: Las Vegas, Nevada
Originally Posted by roamer37
Jack up one wheel have someone crawl under the truck and count how many driveshaft turns you get... turn the wheel 20 rev...and you will get a number like 46.3 or 41.0 move the decimile point one to the left...and you will have it
I really appreciate everyone's input.
Now tell the truth, isn't this FUN!!
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Joined: Aug 2006
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From: Kent WA
Originally Posted by roamer37
Jack up one wheel have someone crawl under the truck and count how many driveshaft turns you get... turn the wheel 20 rev...and you will get a number like 46.3 or 41.0 move the decimile point one to the left...and you will have it
I wouldn't want to try to count 40 or 50 revs of the driveshaft - too easy to loose track.
With an "assistant" to turn the jacked-up wheel it should be pretty easy. Use chalk to mark the wheel (so you know when you've turned it exactly two revs) and the driveshaft (to help keep a good count on the revs).
Last edited by CheaperJeeper; Jan 8, 2007 at 04:53 PM.
Posting Guru
Joined: Aug 2006
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From: Kent WA
Originally Posted by roamer37
Two turns works just as well as long as the ratio is not close to each other sometimes things get hard to tell 4.10 turns or 4.11 turns
In fact, I'm not even sure both ratios really exist. Every 4.10 gearset I've seen has a 10 tooth pinon and a 41 tooth ring gear. No other combination will work - at least not in gears the size that will fit in a differential. So how do you get a 4.11 ratio?
You also hear reference to both 3.55s and 3.56s, but with an 11 tooth pinon and a 39 tooth ring gear the actual ratio is 39 / 11 = 3.54545454...... which rounds up to 3.55. So how would you actually get a 3.56 ratio?
Even if you DOUBLE the numbers of teeth and add or subtract one you don't get 4.11 or 3.56
82 / 19 = 4.315 and 83 / 20 = 4.15, both are more than .01 higher than 4.10
Same for the 3.55s
78 / 21 = 3.714 and 79 / 22 = 3.591
So can anyone explain to me how they come up with these odd numbers? Just one of those things I've always wondered about.....
