front and rear differentials

[DAN V]

Hey guys, I am getting ready to order some parts for the truck and was just curious about the front and rears? Is the front a 9. 25 axle. Is the rear a 11. 50? Do I just need one gasket for each? What kind of lube do you guys use? Any info would be greatly appreciated.

 

[SRadke]

9. 25 front and 11. 5 rear. Cover gaskets are reusable, just clean up and reinstall. Factory spec is synthetic 90wt.

-Scott

 

[DAN V]

thanks

thanks for the info, much appreciated!

 

[dan.poitras]

I've been drilling the bottom of the "pumpkins" and tapping to accept a 1/8 NPT magnetic plug

 

[seafish]

drill and tap your pumpkins

I've been drilling the bottom of the "pumpkins" and tapping to accept a 1/8 NPT magnetic plug

Yup... I did the same thing!!!

I used the 1/8" npt magnetic drain plug from a Harley motorcycle (OEM part#734), like this one here--

24 x 1/8 NPT Hex Oil Tank Magnetic Drain Plug for 1987-1989 Harley Big Twin: 41-163 Aftermarket Harley Davidson ® Motorcycle and Custom Parts and Accessories - Debrix Cycles - www.debrix.com

BUT mine has an allen head and an o-ring seal. Got 2 of them from the local hog shop for $7. 95 each. The first time I did the diff fluid change by taking off the pumpkin covers, I found a sweet spot to drill and tap, down low, where it would not interfere with anything, I slightly counter sunk the hole to make a place for the screw and o-ring to set.

Last week, I used them for the first time to change the diff fluids again, after driving the truck all day to get the fluids nice and warm.
First I cleaned up and loosened the fill plugs to make sure that I could get them out to refill the pumpkins later , as well as let air in to drain the old oil out.
Then I pulled the Harley drain plug. All the old fluid came running out, nice and easy, no need to pull the covers. Little bit of powder on the magnet, but nothing abnormal.
I let both pumpkins drain overnight in the garage, went down again in the morning, tightened the drain plug, refilled with full synthetic 85-90w that I bought in a 5 gallon bucket, using a bucket pump with a lenght of hose made the refill go nice and easy and clean. The 5 gallon bucket was only $120, including tax, at Fleetpride, and has enough for 2 full changes and a couple of top-offs if needed. That's only $20 a gallon!!! It's made by Smitty Lube in the US.

Overall, this is a nice and trick little mod that's super easy to do as long as you are drill and tap proficient. It sure does make changing the diff fluid super easy at 15k intervals, and if you want or need to inspect the inside of the pumpkin at longer intervals, you can still do it the old way and pull the cover--nothing about this mod stops you from doing it the regular way if you want to.

AND AS A BONUS, you get a genuine Harley part on your genuine Dodge truck with your genuine Cummins engine. Oo.
Of course who knows anymore where all these parts are made. :-laf

PS--please note that the link above is for an aftermarket drain plug, not a Harley original, but the oem part# is the same.

 

[Jim W]

I use a Mag-Hytech cover on the rear diff with an extra two quarts of Amsoil 75-90W oil. The Mag-Hytech has a dipstick that has a magnetic probe attached that allows you to remove debris and to check level. This also has a pipe plug tapped for a temp probe if you want to install one. There is also a fill plug in the center if you want to use it.

I am on vacation now and towing my 5 er have been checking the rear diff and my temps are a constant 135F with an ambient air temp of 65F.

Will worth the money for this and the added piece of mind I also have one on the transmission. Will be adding one to the front soon.

Just my $0. 02

 

[RVTRKN]

Yup... I did the same thing!!!



I used the 1/8" npt magnetic drain plug from a Harley motorcycle (OEM part#734), like this one here--



24 x 1/8 NPT Hex Oil Tank Magnetic Drain Plug for 1987-1989 Harley Big Twin: 41-163 Aftermarket Harley Davidson ® Motorcycle and Custom Parts and Accessories - Debrix Cycles - www.debrix.com



BUT mine has an allen head and an o-ring seal. Got 2 of them from the local hog shop for $7. 95 each. The first time I did the diff fluid change by taking off the pumpkin covers, I found a sweet spot to drill and tap, down low, where it would not interfere with anything, I slightly counter sunk the hole to make a place for the screw and o-ring to set.



Last week, I used them for the first time to change the diff fluids again, after driving the truck all day to get the fluids nice and warm.

First I cleaned up and loosened the fill plugs to make sure that I could get them out to refill the pumpkins later , as well as let air in to drain the old oil out.

Then I pulled the Harley drain plug. All the old fluid came running out, nice and easy, no need to pull the covers. Little bit of powder on the magnet, but nothing abnormal.

I let both pumpkins drain overnight in the garage, went down again in the morning, tightened the drain plug, refilled with full synthetic 85-90w that I bought in a 5 gallon bucket, using a bucket pump with a lenght of hose made the refill go nice and easy and clean. The 5 gallon bucket was only $120, including tax, at Fleetpride, and has enough for 2 full changes and a couple of top-offs if needed. That's only $20 a gallon!!! It's made by Smitty Lube in the US.



Overall, this is a nice and trick little mod that's super easy to do as long as you are drill and tap proficient. It sure does make changing the diff fluid super easy at 15k intervals, and if you want or need to inspect the inside of the pumpkin at longer intervals, you can still do it the old way and pull the cover--nothing about this mod stops you from doing it the regular way if you want to.



AND AS A BONUS, you get a genuine Harley part on your genuine Dodge truck with your genuine Cummins engine. Oo.

Of course who knows anymore where all these parts are made. :-laf



PS--please note that the link above is for an aftermarket drain plug, not a Harley original, but the oem part# is the same.

It also helps in cleaning them out with solvents. I've had to do it the hard way once, never again with that mod. I will do that when all of my other projects are done, in 2020 the way things are going at this point in my life. Thanks for the idea!

 

[seafish]

It also helps in cleaning them out with solvents. I've had to do it the hard way once, never again with that mod. I will do that when all of my other projects are done, in 2020 the way things are going at this point in my life. Thanks for the idea!

What kind of solvent would you use?? Maybe diesel??



ps--NOT my original idea, but a great one nonetheless. I wish that I could find the obscure original post that I read where someone here at TDR suggested it. Maybe it was dan. poitras ??

 

[dan.poitras]

Check this out

https://www.turbodieselregister.com...-2003-2007/181830-rear-end-2.html#post1835509

 

[seafish]

Check this out

https://www.turbodieselregister.com...-2003-2007/181830-rear-end-2.html#post1835509

Yup. . that must be it, though I also recall some "old timer" mentioning it inside a much longer, more obscure post... . no matter... Great minds think alike and this is definitely a simple and great mod!!

 

[Wingate]

I went to 75W-140 Valvoline Synthetic in the rear diff. on my truck due to high ambient air temps here in the summer. I also tow alot and while we don't have mountains around here, we have millions of short steep hills that really drive up differential temps. when towing. I also installed Mag Hytec covers to increase capacity.

 

[Briman]

I use a Mag-Hytech cover on the rear diff with an extra two quarts of Amsoil 75-90W oil. The Mag-Hytech has a dipstick that has a magnetic probe attached that allows you to remove debris and to check level. This also has a pipe plug tapped for a temp probe if you want to install one. There is also a fill plug in the center if you want to use it.
I am on vacation now and towing my 5 er have been checking the rear diff and my temps are a constant 135F with an ambient air temp of 65F.
Will worth the money for this and the added piece of mind I also have one on the transmission. Will be adding one to the front soon.
Just my $0. 02

How are you checking the temperature? Are you using an infrared thermometer? I use another brand of cover and have a thermocouple installed. When it reads 180 on the inside I get exterior readings similar to yours (135-140) with a Fluke gun. I lean on the bumper of my truck and point the laser dot at the center of the diff. From this distance the thermometer is averaging the temp from the entire pumpkin, perhaps more.
When using an infrared thermometer; the further away you are the greater the measurement circle becomes.

Back to the OP's topic. I went back to 75-90 after using both 75-140 and 80-140. You don't need to buy gaskets. All I do on my front differential (and on the rear too until I changed the cover) is loosen the bolts and let the oil drain out into a pan. I catch some of the oil in a clear glass jar so I can look for metal flakes and out of the ordinary impurities with a bright light. After the first rush of oil I pull the cover away from the housing and let it drain for awhile. After it's empty simply tighten the bolts and fill back up. A good shot with a power washer cleans things right up. Like Seafish, I always make sure I can get the fill plug loose before I start the draining. I also like the idea of drilling and tapping for a drain plug and may do this to my front.