SIL 07-TR-20
July 22, 2020
Page 1 of 2
SUBJECT:

Thrust Washers for X1100 and X200 Series

MODELS AFFECTED:

X1100 SeriesTM, X200 SeriesTM

Introduction:
To remain compliant with industry standards, the material of the thrust washers in the X1100 and X200 Series is
changing from bronze to a graphite-infused polyimide. The new polyimide washers are available now. The bronze
washers will remain available as long as supplies last.
Function is unaffected for all 12 washers listed in Table 1. However, the form of all 12 washers is changing because
the old and new washers will be visually distinct due to the material change from bronze to Vespel® polyimide.
The only part with a change to fit is P/N 12552308. In addition to the material change, this washer has been made
twice as thick as the old washers being replaced. This washer is used within the P1, P2, and steer carriers of the
X1100 Series, and we were able to replace both the bronze (P/N 12267815) and steel (P/N 12267600) washers
with a single Vespel washer that is twice as thick. The overall fit between the carrier, washers, and pinions is
ultimately unaffected because the new washer takes up the same space as both old washers combined.
The other 11 washers are dimensionally identical to the old bronze versions being replaced, so there is no
change to fit elsewhere.

Why Is the Material Changing from Bronze?
The current bronze alloy is being replaced because it contains a significant amount of lead, which is being phased
out industry-wide due to RoHS. Furthermore, our thrust washer supplier informed us that sourcing the particular
leaded bronze alloy was becoming increasingly difficult, and recently it became impossible for them to source.
To ensure production could continue, we had to implement a material change. We worked with the supplier to
investigate lead-free bronzes, but ultimately they could not provide a material that would serve as an effective
substitute. Therefore, in addition to changing materials, we also had to change suppliers.

What Is the New Material?
The new material we chose is called DuPontTM Vespel SP-21. It is a graphite-infused polyimide material with
excellent anti-wear properties and is frequently used as a lead-free replacement material for thrust washers at
Allison and elsewhere in industry. For example, this same material has been used to make the thrust washers on
the output carriers of the X200-4A Series for many years, and we have had no notable issues historically. It is also
used in several positions of the X1100 Series transmission for the Abrams Main Battle Tank.

JR / SL8699EN

5150033

Copyright © 2020 Allison Transmission, Inc. All Rights Reserved.

SIL 07-TR-20
July 22, 2020
Page 2 of 2
Table 1. X1100 and X200 Series New Thrust Washers
Old P/N

New P/N

Product Line

12267815

12552308

X1100

12267328

12552310

X1100

12267332

12552342

X1100

12267573

12552373

X1100

12268053

12552374

X1100

29533333

29562856

X1100

6839375

29562850

X200

6839376

29562851

X200

6839514

29562852

X200

23013453

29562853

X200

23018154

29562854

X200

23018282

29562855

X200

Copyright © 2020 Allison Transmission, Inc. All Rights Reserved.