I am newly registered to this site, however i have been reading it for quite some time now. I have gained some great insight to the this new Dmax of mine(previously had 2000 Ford F-250). I went with the flowmaster muffler based on info from this site and have loved it.


I read hoot's excellent article on the rear diff. under the "do it yourself" section. I have one simple question-- does the rear diff have a drain located on the bottom of the housing? Have read some articles stating that i must remove the cover to drain the fluid but looks to me like a drain plug is on the bottom of mine. Thanks for the info and keep up the good work on an excellent site.

Drain plug is right there. A simple job. There is a magnet on it to collect the magnetic "crud".


Just remove, clean, replace and add 4 qts. (till you see/feel it) at the top. I use Mobile 1 synthetic but the 'official' fluid is the GM 'grapejuice'.

Yep! It's really easy as mentioned. You don't even have to jack up the truck.


Buy one of those screw on tops with the 1 foot plastic hose on it. It sure makes adding the fluid easier. Also lowering the spare tire makes adding the fluid easier. Remove the fill plug first... Just a saftey thing. You don't want to drain all the oil, only to find out that you can't get the fill plug off http://dieselplace.com/forum/smileys/Embarrased.gif.


I changed the rear diff at 1500 miles. A lot of very fine silvery material in the fluid and it was dark. It looked like mostly wear in and maybe some factory millings. The big surprise is only 2 quarts drained out! No leaks visible. I used the "grape juice" (The nick name for the GM product.) I purchased online for $17 a quart. The dealer wanted $28. It took 4 quarts. The bottle lists a bunch of long-named ingredients. Not sure if that makes it any better?
May I suggest changing the front differential also? When I changed the front differential at 4000 miles it looked worse then the rear. It also was low. To refill it took 2 quarts of standard 80W-90-gear oil.

I also changed the transfer case @ 4000 miles the oil was reddish and smelled ok but it also had some fine silvery particles. That also was low! That took just under 2 quarts of Dextron 3 ATF. (For the electric button 4X4 case.)Edited by: JohnnyO

What's tricky is finding the drain plug. Mine was actually flush with the bottom of the differential. It's the square hole. The bare end of a 3/8" (or 1/2"??) wratchet fits right into that square hole. You don't even need a socket. (It took me a while to actually figure that out. Duh!!)

For you guys that haven't seen the quality of a Mag-Hytek rear dif cover check this out. Has it's own magnetic dipstick.

http://www.uscom.com/~hoot/cars/duramax/gmc/mag-hytec/images/DSCN1150.jpg

Here's the rest of my pics...


Mag Hytek (http://www.uscom.com/~hoot/cars/duramax/gmc/mag-hytec/index.htm)

I agree with hoot. i have the same mag-hytec cover and i haven't seen many products that equal its quality. my favorite parts are the dipstick, magnet, and large opening for filling.





i would recommend to anyone!

I couldn't get over the machin quality of this thing...

http://www.uscom.com/~hoot/cars/duramax/gmc/mag-hytec/images/DSCN1146.jpg

http://www.uscom.com/~hoot/cars/duramax/gmc/mag-hytec/images/DSCN1141.jpg

http://www.uscom.com/~hoot/cars/duramax/gmc/mag-hytec/images/DSCN1133.jpgEdited by: hoot

Thanks guys, i figured that i had found a drain on the bottom of the diff. but it did not agree with some of the info that i had read/ heard about having to remove the cover to drain. I had planned on changing front diff and transfer case as well based on what i had read on this site previously. Thanks for the info it is always good to get info from someone who has done the job.http://www.dieselplace.com/forum/smileys/Clap.gif


Where is the best price on the mag-hytec cover? Thanks again and keep up the good work.

I also agree with Hoot and DP on this diff cover, a high quality part. Had the chance to tour the shop where they are made when I picked mine up. Very nice operation. Here is the web site:


http://www.mag-hytec.com


Also, nice BB you guys have herehttp://www.dieselplace.com/forum/smileys/Clap.gifEdited by: Kent Tuttle

Too bad they don't have the Allison pan yet http://www.dieselplace.com/forum/smileys/Disapprove.gif (sometime in March)

Hey HOOT, HOW MUCH FOR ONE FOR MY 03-3500?http://www.dieselplace.com/forum/smileys/Thumbs Up.gif Edited by: mpl897

<font size="4">H</font>ey HOOT, HOW MUCH FOR ONE FOR MY 03-3500?http://www.dieselplace.com/forum/smileys/Thumbs Up.gif

I'll let the local vendors here take a shot at it if they offer them. The price is around $265 but it can be had cheaper by calling and asking for better pricing.

It comes with all stainless steel socket head cap screws and washers. No gasket.... Uses an o-ring.

Maybe one of the guys on here will chime in.