Limited Slip Differential for class C
I have a majestic 23 foot class C on a e350 chasis. I would like to take it out snowmobiling but the last two times I have tried I got stuck in the parking lot. Only 1 side of the back dully tires spi...
Forum Discussion
You probably have the same axle dimensions as the dually Ford pickups of about the same year. Rickson truck website says that the 84 and newer E-series vans use 8 bolt 6.5" diameter bolt patter. And that 84 - 97 pickups had that same bolt pattern. So look for a 84 - 97 dually tuck in a junkyard. It should have a non-limited slip rear axle, except for that rare truck (probably a 4X4) that will actually have the factory optional rear axle with the correct rear axle codes such as 4W or 4L on the drivers side door sticker. Many junkyards will list the rear axles on a web link.
If you get a drum to drum width, you should be able to locate the same width rear axle in a junkyard out of a pickup with limited slip rear axle from the factory, and pick that one up for a few hundred dollars.
http://www.fleet.ford.com/towing-guides/
Click on the towing guide. Click on your model year van. Look for the 'axle codes'. I found this chart on page 31 of the 2011 towing guide. However I did not find this chart in the 2004 or 2005 towing guides.
How to Find Your Truck’s Axle Ratio
If you do not know the axle ratio of your vehicle, check its Truck
Safety Compliance Certification Label (located on the left front door
lock facing or the door latch post pillar). Below the bar code, you will
see the word AXLE and a two-digit code. Use this chart to find the
axle ratio that corresponds to that code:
N on-Limited Slip L imited Slip
Vehicle Rear Axle Ratio Rear Axle Code Rear Axle Code
Ratio Normal Limited Slip
Super Duty
3.31 31 3H
3.55 35 3J
3.73 37 3L
4.10 41 4N/4W*
4.30 43 4L
4.88 48 8L
5.38 53 5L
You will be best off with the 4.10:1 rear axle ratio, so look for a 4N or 4W. 4.3:1 is also acceptable, with about 5% higher RPM's at any given road speed, and your speedometer will be off a little bit. About 4 MPH at 65 MPH. Most E-350's came with a non-limited slip 4.10:1 rear axle ratio. It would be rare, but possible to find a E-350 with a 3.73:1 rear axle ratio.
3.73:1 rear axle ratio (3L) is also fine, you will be able to stay in drive much higher speeds (well 5% higher) and probably need to shift out of overdrive more often on a slight hill. 3.55 is not really acceptable with such a large frontal area on your RV, and you would be out of overdrive a lot of the time you are going uphill. Even running on a level section of freeway, you would need to lock out overdrive if it is shifting from drive to overdrive often, and it might when using a 3.55:1 rear axle. The engine speed at 55-60 MPH will not be high enough to stay in overdrive as much as you do now.
You can check RicksonTruck.com and see what years the E-series had for what bolt patterns. If you want to stay with the same bolt pattern, you then look up the pickups with that exact same rim application and see what model years they use the 8 bolt pattern (in metric or on a 6.5" pattern or whatever is the case for your year RV). So you might be thinking "Why not get a 2005 and newer F-350 rear axle and it's 3,400 pound rated 18" rims and 8 bolt 200 mm (5.3") metric bolt pattern?" Well your front rims are set up for the 6.5" diameter bolt pattern, and would not fit the 18" 200 mm bolt pattern rims up front, so you might need two spares if you have different bolt patterns front and rear axles.
As for going to a axle shop, and having the rear axle ratio swapped, that might cost anywhere from $1,000 to $2,500, you would need to get a quote from them.
Good luck!
Fred.
If you get a drum to drum width, you should be able to locate the same width rear axle in a junkyard out of a pickup with limited slip rear axle from the factory, and pick that one up for a few hundred dollars.
http://www.fleet.ford.com/towing-guides/
Click on the towing guide. Click on your model year van. Look for the 'axle codes'. I found this chart on page 31 of the 2011 towing guide. However I did not find this chart in the 2004 or 2005 towing guides.
How to Find Your Truck’s Axle Ratio
If you do not know the axle ratio of your vehicle, check its Truck
Safety Compliance Certification Label (located on the left front door
lock facing or the door latch post pillar). Below the bar code, you will
see the word AXLE and a two-digit code. Use this chart to find the
axle ratio that corresponds to that code:
N on-Limited Slip L imited Slip
Vehicle Rear Axle Ratio Rear Axle Code Rear Axle Code
Ratio Normal Limited Slip
Super Duty
3.31 31 3H
3.55 35 3J
3.73 37 3L
4.10 41 4N/4W*
4.30 43 4L
4.88 48 8L
5.38 53 5L
You will be best off with the 4.10:1 rear axle ratio, so look for a 4N or 4W. 4.3:1 is also acceptable, with about 5% higher RPM's at any given road speed, and your speedometer will be off a little bit. About 4 MPH at 65 MPH. Most E-350's came with a non-limited slip 4.10:1 rear axle ratio. It would be rare, but possible to find a E-350 with a 3.73:1 rear axle ratio.
3.73:1 rear axle ratio (3L) is also fine, you will be able to stay in drive much higher speeds (well 5% higher) and probably need to shift out of overdrive more often on a slight hill. 3.55 is not really acceptable with such a large frontal area on your RV, and you would be out of overdrive a lot of the time you are going uphill. Even running on a level section of freeway, you would need to lock out overdrive if it is shifting from drive to overdrive often, and it might when using a 3.55:1 rear axle. The engine speed at 55-60 MPH will not be high enough to stay in overdrive as much as you do now.
You can check RicksonTruck.com and see what years the E-series had for what bolt patterns. If you want to stay with the same bolt pattern, you then look up the pickups with that exact same rim application and see what model years they use the 8 bolt pattern (in metric or on a 6.5" pattern or whatever is the case for your year RV). So you might be thinking "Why not get a 2005 and newer F-350 rear axle and it's 3,400 pound rated 18" rims and 8 bolt 200 mm (5.3") metric bolt pattern?" Well your front rims are set up for the 6.5" diameter bolt pattern, and would not fit the 18" 200 mm bolt pattern rims up front, so you might need two spares if you have different bolt patterns front and rear axles.
As for going to a axle shop, and having the rear axle ratio swapped, that might cost anywhere from $1,000 to $2,500, you would need to get a quote from them.
Good luck!
Fred.
