Shandong Shengyue Technology Development Co.,Ltd is one of the most professional fast 12-speed heavy-duty truck transmission 1st & 2nd gear synchronizer assembly 12jsdx240t-1701170 manufacturers and suppliers in China. Please feel free to buy high quality genuine auto parts at competitive price from our factory.
FAST 12-Speed Heavy-Duty Truck Transmission 1st & 2nd Gear Synchronizer Assembly 12JSDX240T-1701170
Common Failure Symptoms
Since the first and second gears of heavy-duty trucks are frequently used for starting under heavy loads and climbing steep slopes, the synchronizer is subjected to immense frictional forces and is prone to wear.
1. Gear Grinding/Abnormal Noise: A sharp metallic clashing sound occurs inside the transmission when shifting into 1st or 2nd gear. This is caused by severe wear on the synchronizer's conical friction ring (brass ring), preventing the main shaft gear and the synchronizer sleeve from matching speeds.
2. Stiff/Sticking Gear Shifting: Significant resistance is felt when shifting into 1st or 2nd gear; in some cases, "double-clutching" is required to force the gear into engagement.
3. Gear Slipping (Jumping Out of Gear): The gear shift lever automatically snaps back to neutral when applying power during start-up or hill climbing. This is typically caused by the synchronizer's engagement teeth wearing down into a tapered shape, causing them to slip out of engagement under load.
1st & 2nd Gear Synchronizer Replacement Bill of Materials (BOM)
| No. | Part Number | Part Name (EN) | Qty | Replacement Category | Remarks / Functional Description |
|---|---|---|---|---|---|
| 1 | 12JSDX240T-1701170 | 1st & 2nd Gear Synchronizer Assembly | 1 set | Mandatory | Core assembly for this repair, including sliding sleeve, tapered ring, and keys. |
| 2 | JS180-1701171 (Ref. No.) |
Synchronizer Tapered Rings (Brass) | 2 pcs | Included in Core (Available Separately) |
Frictional brass rings. If not included in the assembly, buy separately; 1st & 2nd gear require 1 pc each. |
| 3 | F96161 / F99692 (FAST Standard) |
Main Shaft Snap Rings / Circlips | 2-3 pcs | Always Replace | Critical rings fixing the axial position. Deforms upon removal; reuse is forbidden to prevent gear drift. |
| 4 | 12JS160T-1707050 (Ref. No.) |
Transmission Housing Gaskets Kit | 1 set | Always Replace | Covers gaskets for main/auxiliary cases and top cover. Must be replaced after splitting the case to prevent leaks. |
| 5 | JS180-1701048-3 (Ref. No.) |
Main Shaft Rear Bearing | 1 pc | Conditional (Highly Recommended) |
Inspect the bearing after lifting the main shaft. Best timing to replace if there is play or noise. |
| 6 | 16763 / 7920 (Fuller/FAST Standard) |
Shift Fork Lock Pins & Safety Wire | 1 set | Always Replace | Lock pins for the 1st/2nd shift fork. Must be re-wired and secured tightly to prevent loosening inside. |
| 7 | F91018 (FAST Standard) |
O-Ring Seals Kit (Auxiliary Cylinder) | 1 set | Conditional | Replaces rubber O-rings of the shift cylinder and double H valve to eliminate slow air leaks. |
| 8 | GL-5 85W-90 (or FAST Special) |
Heavy-Duty Gear Oil (GL-5) | Approx. 12-14L | Always Replace | Old oil must be drained when splitting the case. Fresh oil ensures proper break-in for new brass rings. |
DETAILS
| DESCRIPTION | 1st & 2nd Gear Synchronizer Assembly | PART NUMBER | 12JSDX240T-1701170 |
| WEIGHT | 5kg | VOLUME | 240 mm × 240 mm × 80 mm |
| TRUCK MOLDE | FAST | QUALITY | Copy,High Copy, OEM,Original |
| MOQ | 1 | WARRANTY | 1 year |
| PAYMENT | TT/WESTEN UNION | SHIPMENT | by air/sea/railway |
| BRAND | SINOSACHS | PLACE OF ORIGIN | JINAN CITY,CHINA |
| STOCK | IN STOCK | APPLICABLE SITE | GEARBOX |
| PACKAGE | Carton/Woodenbox | PORT OF LANDING | Qingdao Port,China |
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