Eaton FSO4405 & FSO4505 Transmission Gear Solutions
Eaton FSO4405 & FSO4505 Transmission Gear Solutions
Eaton FSO4405 & FSO4505 Transmission Gear Solutions
When rebuilding or servicing 5-speed synchronized manual transmissions like the FSO4505, shift quality and durability depend on synchronizer condition, cone geometry matching, and stable gear tooth accuracy. We supply aftermarket replacement gears, shafts, and synchronizer components cross-referenced by OEM numbers—supported by quality evidence for repeatable assembly outcomes.
Key Facts:
Transmission family: 5-speed synchronized light-duty manual transmission; model includes FSO-4505.
Shift system note: FSO-4505 has five forward speeds and synchronized gearing; misuse can accelerate synchronizer wear.
What we supply: gears, mainshaft/countershaft parts, synchronizer rings & assemblies (OEM-number cross reference).
Send us your OEM part number / photo / drawing for a fast cross-reference and quote.
1. Customer & Application
Customer type:
A regional transmission rebuilder and parts distributor needed a stable source of replacement components for Eaton FSO4405 and FSO4505 units used in light/medium-duty truck fleets.
Application:
5-speed synchronized manual transmission rebuilds focused on restoring smooth engagement, reduced gear clash, and reliable torque transfer. Synchronizers are designed to match shaft and gear speeds to enable smooth shifts.
2. Customer Pain Points (What they asked us to solve)
2.1 Hard shifting / gear grinding after service.
2.2 Uncertain interchange: wrong cone angle / incorrect mating fit leads to rework.
2.3 Inconsistent life: unstable heat treatment or surface integrity can accelerate wear.
2.4 Need OEM-number ordering to reduce mistakes in procurement.
3. Product Scope (OEM-number cross reference)
We cover common service parts for both transmissions, including:
• Gears (countershaft/mainshaft, 1st–5th speed related items)
• Shaft parts (mainshaft, countershaft related)
• Synchronizer components (rings, assemblies, hubs, sleeves)
▶FSO4405 Transmission Exploded View
▶FSO4405 Parts Summary Table
| No. | PairGears No. | OEM No. | Part Name | Mating Gear | Online Product Page |
1 | PGEA123 | 3361224 | Synchronizer 5A | ||
2 | PGEA547 | 3344765 | Synchronizer 3/4 | ||
3 | PGEA548 | 3344755 | Synchronizer 1/2 | ||
4 | PGEA132 | 3344768 | Synchro Ring 3/4/5 | ||
5 | PGEA129 | 3344778 | Synchro Ring 3/4 | ||
6 | PGEA130 | 3344534 | Synchro Ring 1/2 | ||
7 | PGEA103 | 3344701 | 3rd Speed Gear -
Mainshaft | 3341184 | |
8 | PGEA102 | 3344769 | 5th Speed Gear -
Mainshaft | 3341107 | |
9 | PGEA108 | 3344777 | Reverse Gear -
Mainshaft | 3341182 | |
10 | PGEA120 | 3344260 | Input Shaft | 3341109
| |
11 | PGEA114 | 3344641 | 2nd Speed Gear -
Mainshaft | 3341390 | |
12 | PGEA107 | 3344522 | 1st Speed Gear -
Mainshaft | 3341390 | |
| 13 | PGEA117 | 3341164 | Mainshaft | ||
14 | PGEA112 | 3341107 | 5th Speed Gear - Countershaft | 3344769 | |
15 | PGEA116 | 3341109 | Drive Gear -
Countershaft | 3344260 | |
| 16 | PGEA101 | 3341184 | 3rd Gear -
Countershaft | 3344701 | |
| 17 | PGEA118 | 3341390 | Countershaft | 3344522/3344641 |
▶FSO4505 Transmission Exploded View
▶FSO4505 Parts Summary Table
No. | PairGears No. | OEM No. | Part Name | Mating Gear | Online Product Page |
1 | PGEA109 | 3361064 | 5th Gear - Countershaft | 3361400 | |
2 | PGEA105 | 3361067 | Drive Gear -
Countershaft | 3361436 | |
3 | PGEA113 | 3361063 | 3rd Gear - Countershaft | 3361402 | |
4 | PGEA119 | 3361300 | Countershaft | 3361295/33610 | |
5 | PGEA131 | 3361096 | Synchro Ring 3/4/5 | ||
6 | PGEA133 | 3361091 | Synchro Ring 1/2 | ||
7 | PGEA125 | 3361397 | Synchronizer 5 | ||
8 | PGEA122 | 3361396 | Synchronizer 3/4 | ||
9 | PGEA127 | 3361242 | Synchronizer 1/2 | ||
10 | PGEA121 | 3361436 | Input Shaft | 3361067 | |
11 | PGEA104 | 3361400 | 5th Speed Gear -
Mainshaft | 3361064 | |
12 | PGEA106 | 3361398 | Reverse Gear -
Mainshaft | 3361058 | |
13 | PGEA111 | 3361402 | 3rd Speed Gear -
Mainshaft | 3361063 | |
14 | PGEA115 | 3361295 | 2nd Speed Gear -
Mainshaft | 3361300 | |
15 | PGEA110 | 3361075 | 1st Speed Gear -
Mainshaft | 3361300 | |
16 | PGEA128 | 3361073 | Mainshaft |
4. How We Delivered
Pre-production
• Confirm OEM number mapping and mating gear pairs to avoid incorrect interchange.
• Identify critical geometry (tooth accuracy, cone angle, fit interfaces) that affects shift feel and assembly success.
In production
• Control tooth geometry consistency to reduce abnormal noise and premature wear.
• For wear-critical transmission components, case hardening such as carburizing is commonly used to achieve a hard surface with a tougher core.
• Where specified, shot peening can introduce beneficial compressive residual stress at the surface.
Post-production
• Provide inspection reports and drawings upon request.
• Pack and label by OEM No. to reduce receiving mistakes for rebuilders.
5. Project Challenges & How We Solved Them
| Project Challenge | What Could Go Wrong | How We Solved It |
| Synchronizer cone / friction-surface matching | Hard shifting, gear clash, or grinding even after parts replacement | We treated cone angle + friction-surface fit as a key acceptance point, verified incoming samples against the mating parts, and locked the control points into our process to keep results consistent. |
| Tooth profile & lead consistency | Abnormal noise (whine) and rough meshing after assembly | We defined profile/lead inspection items (e.g., lead, profile, runout as applicable) and standardized them into a redacted outgoing inspection report for repeatable assembly results. |
| Heat-treatment stability | Early wear, pitting, or surface distress in service | We controlled surface hardness and case depth as the core CTQs and, when needed, added redacted metallographic verification to confirm the hardened layer and microstructure. |
FAQ
1. Do you supply parts for both FSO4405 and FSO4505?
Yes. Share your OEM number list (or photos), and we'll confirm interchange and matching pairs.
2. Are these parts drop-in replacements?
They are manufactured to OEM-number cross reference and intended for direct replacement; final results depend on gearbox condition and correct rebuild practices.
3. What information do you need for a quote?
OEM No., quantity, target lead time, and any special requirements (material/heat treat/inspection).
4. Can you provide inspection reports and drawings?
Yes—redacted inspection reports and drawings can be provided for review (project-dependent).
5. Do you support small trial orders?
Yes. We can support sample or pilot quantities before ongoing supply.
If you're rebuilding Eaton FSO4405/FSO4505 units and want stable shift quality and repeatable fit, send your OEM part numbers for cross-reference and quotation.
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