Do I need friction modifier with Royal Purple gear lube

[jwsnake56]

I am prepping the rear axle that was rebuilt for my project. It is from a '94 Mustang GT - converted to Fox width with new Moser 5 lug axles, rebuilt trac-lok, new FRP 3.55 gears, bearings, and seals. I bought some Royal Purple MaxGear 75W-90 gear oil for the axle. It says "with friction modifier additive" on the label. So, I do not need to add any Ford Racing friction modifier to the axle - just the Royal Purple? I don't want to damage the fresh differential mechanicals. Thanks.
John S.
Mk4 Roadster 8866

[frankeeski]

Here is my advise on this John. Years ago my gear guy insisted that the first fluid used in a Ford Trac-Loc after rebuild needed to be standard dino oil with friction modifier added. He told me that the friction clutches in those units didn't react well to full synthetics. He told me that after the first change of fluid synthetics were fine, I've always followed his advise and never had a problem. My advise would be to use what ever gear oil and additive the re-builder or rebuild manual/instructions tell you to use.

[CraigS]

OTOH Wade Chamberlain recommended Mobil1 many years ago when I rebuilt my TracLoc. I used it w/o modifier for about 4 yrs after that including about 18 autocrosses per year. Worked fine.

[NukeMMC]

I soaked my clutch pack in Friction Modifier for about a week before installation. After assembly I filled with MaxGear and added no modifier. Has been running fine for 4000 miles so far.

[Purple Venom]

None was used with mine when it was re-assembled. Same setup as yours.

[AC Bill]

Did you soak your friction discs before assembly?

I used Royal Purple c/w friction modifier from the get go, and have had no issue. When the rear end was being rebuilt, like Bruce, I soaked the new friction discs in Ford OEM modifier before assembling, (as per the Ford factory service manual). 5000+ miles, no issues.

[avgjoe]

I believe the friction modifier was used by Ford to limit chatter in the clutch packs under low speed, tight cornering; purely for NVH concerns. IMO, it serves no other real purpose other than stinking up you garage. Use or don't use it, I don't think you will hurt your diff.

[jwsnake56]

Thanks for all the feedback. The rebuilder listed "one bottle friction modifier" on the build sheet. My understanding is that the discs were soaked in the stuff and the rest was added to the diff with no fluid prior to shipping. Now I just have to install the "banana bracket" onto the housing. The darn thing seems like it is too small to fit onto the housing tube. We'll see.
John S.

[ehansen007]

It will fit. You may need to spread it just a bit to get it started but it will fit. Also, be sure to tack a few beads on there with the old welder to keep it in place. Ask me how I know.... :)

[Avalanche325]

I did Royal Purple and friction modifier. I think that completes the thread now that you have gotten every combination possible.

6500 miles. Lots of autocross. No issues. Well, except for the stinky garage for a couple of days.

[dmoran]

... Now I just have to install the "banana bracket" onto the housing. The darn thing seems like it is too small to fit onto the housing tube. We'll see.
John S.

I had a hell of a time getting the 2 halves of my banana bracket to line up in order to insert the bolts. (Never thought I'd say that) Anyway,I grabbed a couple bolts that were longer and thinner than the ones in the kit and tightened them alternately until the holes in the 2 halves lined up. Then one by one, I put the original bolts in. For each one, I had to play with tightening and loosening the others to get the next set of holes to line up. Eventually they all went is and torqued into place with no problem. Also, I had to run a drill through the holes to clear out the powder coating. Like jwsnake56 said, after all that, it's standard practice to add a couple tack welds between the bracket and axle tube.

BTW - I just went with straight Royal Purple but haven't driven it yet.

Doug

[AC Bill]

I had a heck of a time fitting the two halves of that bracket together as well. Ended up stripping one bolt, as the threads were running up against the bracket, as it screwed into the nut. You'd think that they would make them the right size for the axle tube? Perhaps it done on a press and the die is worn out, or if made from a section of pipe cut in half, they couldn't find pipe the correct size...

By all means tack weld them, and/or use a VPM brace, or one similar that you make up. I added a brace as well just to keep things from possibly twisting.

[cnutting]

I just installed mine. Wire brushed all of the powder coat off the inside of the brackets and where the bracket contacts the axle (plus a little extra for the weld prep), loosely lined up the cap with two bolts and a tapered pry rod in the hole for the pumpkin flange. I then ran a 1/2" drill through the two remaining holes, switched the bolts and ran through the other two. Since I had 2/3 of the diameter on the pumpkin flange, I ran a drill through that hole then put the SHCS in and tightened. Last was going back and torquing the four bolts for the cap which went fairly easy. Good contact with the axle. Then the welder came by and ran a bead on both sides of the cap.

Chris

[Mesa Mike]

Standard Ford rear-end gear oil with friction modifier and working well for 16 years.