Completing our URAL differential trilogy (after the case 375-2403022 and the side gear 375-2403050-20): the planet gear 375-2403057 (Russian: сателлит дифференциала) — the small 0.5 kg gear that makes a differential a differential. Without it, your driven wheels could never turn at different speeds.
What the planet gear does
The planet (spider) gear rides on the cross pin inside the differential case and meshes with both side gears. In a straight line it simply rotates with the case, carrying torque to both axle shafts equally. The moment the truck turns, the planet gear rolls on the side gears, letting the outer wheel spin faster than the inner one — that rolling action is the entire reason a differential exists.
It is a small gear doing brutal work: high tooth loads, constant sliding contact, and marginal lubrication the moment axle oil ages. Pitting and scoring on planet gears are among the most common findings in a URAL axle teardown.
Specifications
| Property | Value |
|---|---|
| Part number | 375-2403057 (also written 3752403057) |
| Name | Planet gear / сателлит дифференциала |
| Brand | URAL |
| Group | Rear axle — differential assembly |
| Weight | 0.5 kg |
| Bushingless analog | 4320-2403057-01 |
Which trucks does it fit?
The middle- and rear-axle reducers of the core URAL 6x6 family:
- Ural-375
- Ural-4320
- Ural-5557
Two numbers to know: 375-2403057 and 4320-2403057-01
The catalogue lists a bushingless analog, 4320-2403057-01 — same role, same ~0.5 kg weight, but built without the bushing. When sourcing:
- Quote 375-2403057 as the primary number.
- If your supplier's stock is the bushingless version, ask for 4320-2403057-01 by name.
- Never mix bushed and bushingless gears in one differential — keep the set uniform.
The golden rule, again
As with the side gears in the previous article, the catalogue is explicit: planet gears are fitted as a set together with the side gears. A complete URAL differential gear overhaul is:
- Planet gears 375-2403057 (all positions in the diff)
- Side gears 375-2403050-20 (one per axle shaft)
- Plus the washers and the cross pin they ride on
Mixing old and new gears in one differential means worn-in contact patterns fighting fresh surfaces — noise, rapid wear, and a second teardown.
Where to look it up
Full specifications and the complete fitment list are on the part page:
375-2403057 Planet gear — kamaz-parts.com
The catalogue covers 87,000+ KAMAZ, URAL, MAZ, MTZ and TATRA part numbers organized by the original OEM drawing structure (brand → model → assembly group → position table), so you can verify any number against the actual assembly drawing before ordering. Wholesale inquiries go straight from the part page — mixed pallets welcome, export paperwork included.
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