As with ALL differentials ours needs a proper break in period.
This allows the gears to work harden and smooth themselves
before hard use for cooler operation. If this isn't done you are
risking expensive damage to the gear set that can only be fixed
by replacing the gear set.

There is no hard and fast rule to cover all situations as to the
proper way to break them in. The key is to get some miles/time
on them in short increments while not allowing them to
overheat and break down the fluid.

In certain situations, especially racing, there is very little time if
any to properly break in the gears.

We are now offering a REM finishing process to the gears to
help with this problem. Most every NASCAR team REMs their
gears to help avoid the heat buildup associated with racing.
This is NOT a guarantee that you will not wear out your gears
from improper break in but it will dramatically increase your
odds and for sure they will run cooler.

The cost of this is $250.00, we are sending them to a company
that does NASCAR gears for this service. The cost comes from
the cost of shipping them there, the process, and shipping
them back to us.

Please allow an extra 14 business days to your order if you
want this done. We may stock some in the future depending
on the demand.

Below are some pics of a Megahi9 set that has been REMed.
Break-in  /  REM
& brg., race, & seal part numbers
Bearing, Race, and Seal part numbers.
35/40 spline AXLE, Hi9 master kit (all bearings, shims, seals,
and solid spacer kit) from Randy's/Yukon

28/31 spline AXLE, Hi9 master kit (all bearings, shims, seals,
and solid spacer kit) from Randy's/Yukon

28 and 31 spline carrier bearings and races:  LM 102949  LM
102910 or Timken Set 47

35 and 40 spline carrier bearings and races:  LM 104949  LM
104911 or Timken Set 38

Standard Hi9 pinion support bearings and races:

Large brg.  HM89443                                                                              
Large race HM89410

Small brg. M88048
Small race M88010

Pinion seal 7044NA

Third brg. R1535TAV

MegaHi9 pinion support bearings and races:

Black Pinion Support:

Large brg. M804049
Large race M804010

Small brg. 3490
Small race 3420

Pinion seal 472409

Blue Pinion Support:

Large brg. HM804846
Large race HM804810

Small brg. 2788
Small race 2729

Pinion seal 472015

WIDE Third brg. M5204TV
Fill with a GL-5 rated 85w-140 standard
(non-synthetic) gear lube to non drilled fill

For rear applications in desert racing use
2 ½ to 3 gallons of Swepco 203 moly- 250
weight available from