Royal Purple

[Mark Rinker]

Last May, at 20K miles I had a major fluid service done while in Phoenix at Midway Chevrolet on the C4500. Since the previous owner hadn't addressed the rear diff yet, I had them replace with Royal Purple synthetic. Spendy, but I didn't want to cut any corners as I have heard of a few C4500s with low mile rear gear problems, and suspected it was due to lack of maintenance after break-in.

Truck turned over 60K this month, had the rear diff checked during oil change. Was expecting to see a typical grey/black fluiid begging to be changed. Instead, what came out looked as purple and clean as what came out of the jug!

Question: If it looks this good after 40K all towing miles, when should I change it?:confused:

[More Power]

The first diff lube service is the most important one. As it was explained to me, there'll be some amount of manufacturing debris left in the rear axle and the new gears & bearings will produce some amount of wear-in metal. It's important to change the fluid soon after the truck is put to work (about 10K), to get the wear metal out. After that, very little wear metals accumulate in the differential. However, there are a couple caveats.... 1- Heat kills the lube qualities. 2- Limited-slip differentials deposit clutch disc wear material in the lube over time.

Always follow your owner's manual recommendation for lube service intervals. Otherwise, if the lube looks OK and smells OK, it probably is.

In 2004, the techs at Randy's Ring & Pinion were adamant that I change the rear diff lube soon after getting Lil Red on the road. Randy's built the GM 14-bolt 9.5 AAM rear differential for that truck, using an Eaton Posi, new gears, bearings and seals. I mentioned to them, at the time, that I only had between 1000 & 2000 miles on the rear diff, but they said change it anyway. So I did.... ;)

Jim

[Mark Rinker]

I'll be back in Phoenix late February, and plan to stop by Midway Chevrolet for the 'annual' big fluid service, including:

Rear differential
Full transmission service
Coolant
Power steering?
Brake fluid?Any way you look at it, its cheap insurance.

[linchhummmer]

another thing that is important is to check all the fluids on a new car alot of times car companys will just fill the rear end enough to get it off the line as well as other fluids. today we did a break in fluid change on an 08 chevy taho and there were chunks of metal in the rear end and the car is only a month old so we are going to send it back and make the dealer put a new rearend put in it. ive been running royal purple in my trucks changing the oil at 15000 with a filter change in the middle, i run it in the power steering, trans and diffs and its a little more costly but i think its worth it if i changed my oil with rotial every 5000 royal purple is still less expensive

[More Power]

another thing that is important is to check all the fluids on a new car alot of times car companys will just fill the rear end enough to get it off the line as well as other fluids. today we did a break in fluid change on an 08 chevy taho and there were chunks of metal in the rear end and the car is only a month old so we are going to send it back and make the dealer put a new rearend put in it. ive been running royal purple in my trucks changing the oil at 15000 with a filter change in the middle, i run it in the power steering, trans and diffs and its a little more costly but i think its worth it if i changed my oil with rotial every 5000 royal purple is still less expensive

It's somewhat "normal" for a some amount of metal flakes and bits to be present inside the bottom the diff - usually stuck to the magnet. I saw the same thing with my 2500HD. It is alarming, but others have reported this as well. That's why people should change it fairly soon....

JIm