How many owners, who drive on the roads and have minimal wheel spin, have had to replace their clutch pack? Mine is growling in turns (after its warmed up) and I think it is because friction modifier was left out after a bearing job about 20K miles ago. When asked at the time why there wasn't any friction modifier on the materials list the answer was 'it is synthetic oil and it doesn't need it.' If I drain and refill, this time making sure the friction modifier is added, will it stop the wear or is the deterioration just going to continue?

 

It will help. I'm not a fan on synthetic gear lube so all of my rigs run dino.

 

Ford uses synthetic gear lube in the rear diff. and if equipped with the LSD still requires the friction modifier. Now that being said some aftermarket gear lubes have the friction modifier already in there formula, I guess the question would be, is what synthetic gear lube was used after the bearing job?

 

I use either Amsoil, Royal Purple or Redline in my diffs - they say their formulas include friction modifiers but chatter can still occur. If it happens, add the minimal amount to make the noise stop. Don't forget to drive in a figure 8 ( and a reverse figure 8) pattern to ensure the new fluid and modifier gets circulated well.

Digger - curious as to why you aren't a fan of synthetics? Especially when it is a factory fill....

 

The factory has different motives- cost and MPG. EVERYTHING revolves around cost and MPG. Synthetics do get slightly better mpg. If your testing is done with synth, your recommendation must be synth.

I've been involved with the diff world for many years. A very large share of my customers were diff installers. Most, probably 80%+, won't use synthetics (gear lube) in their own rigs. Currie Enterprises, as an example (a huge builder of HP rear ends) will void your warranty if you use synthetics. Another customer, whom needs to remain nameless, provided the 3rd member for a race team sponsored by a synthetic lube mfgr. They couldn't make the R&P live until switched to dino lube. Another customer in Detroit partnered up with GM and did some testing on heat build up. They had 3 separate diff setups they were testing. Standard (dino) lube, standard cover- synth lube, stardard cover- synth lube, finned cover. Their results were both expected AND very surprising. As expected the synth fluid with finned cover was coolest, the synth with std cover was next and the dino lube with standard cover was the warmest. What they didn't expect was the temp of the diff itself. It seems that the molecular design of the synthetic fluid must shed heat. Unfortunately there isn't enough surface area on the cover and housing to shed heat fast enough. The diff itself actually got warmer and was acting as a heat sink. The diff fluid was warmer in the dino filled unit, but the diff itself was cooler.

This subject has been the focus of huge debate and I side with the installers. I don't care what the engineers say. To me, history and real world experience with thousands of diffs provide me with the comfort I need to use dino gear oil.

 

Thanks Digger. I wasn't aware that Currie spec'd out dyno oil vs. synthetics. I wonder if the newer diff covers (finned aluminum) help with the heat extraction any. Might be a good way to justify the upgrade to my significant other... :-)

Edit - went to the Currie site and looked at their install instructions - interesting note which confirms Digger's post: "Never use any type of synthetic oil, synthetic-blend oil, store brand oil, or Sta-Lube brand oil."

Learn something everyday on this forum!

 

The finned covers do help dissipate heat. When the first Nissan Titans came out the were frying their diff lube. The factory recall added finned covers. I used a factory 2008 cover on my X.