A propeller shaft longer than about a metre and a half is usually made in two pieces, joined in the middle and supported there by a centre bearing — a sealed ball bearing held in a rubber cushion bolted to the chassis. The bearing carries the shaft; the rubber absorbs vibration and lets the shaft move as the axle rises and falls. When either fails the vehicle vibrates, and the fault is regularly blamed on tyres, wheel balance or universal joints. This article covers the parts, how to tell a centre bearing from a U-joint, and what to record before ordering.
ရှည်လျားသော propeller shaft ကို အလယ်တွင် ဆက်ထားပြီး center bearing ဖြင့် ထောက်ထားသည်။ ပျက်စီးပါက ကား တုန်ခါပြီး ဘီးပြဿနာဟု မှားယွင်း ထင်တတ်သည်။
In This Article (ဆောင်းပါးအကြောင်းအရာများ)
1. What the assembly contains
2. How it fails
3. Telling it from a universal joint
4. Why it is replaced with the U-joints
5. What to record before ordering
6. Fitting — phasing and preload
7. How to order from Win Auto Parts
1. What the Assembly Contains
အစိတ်အပိုင်းများ
| Part | What it does | Sold as |
|---|---|---|
| Centre bearing | A sealed ball bearing carrying the shaft at the joint between the two sections | Bearing alone, or within a complete support |
| Centre bearing cushion | The rubber ring that holds the bearing and isolates vibration | Cushion alone — several lengths and bore sizes exist |
| Centre bearing support | Bearing and cushion together in their bracket, ready to bolt on | The usual purchase |
| Centre bearing kit | Support plus the hardware, and sometimes a dust shield | Where the bolts and shields are also corroded |
| မြန်မာ | Bearing, ရာဘာအခုံ နှင့် ကွင်းဆက် | Support အပြည့် ဝယ်ခြင်းက အများဆုံး |
2. How It Fails
ပျက်စီးပုံ
- The rubber cushion perishes. Heat, oil and age crack it; the bearing then moves with the shaft instead of holding it still.
- The bearing seal fails. Water and grit enter, the grease is lost, and the bearing becomes rough and then seizes.
- The cushion separates from its bracket, letting the shaft drop slightly and run at the wrong angle through both joints.
- Corrosion of the bracket and bolts, common on vehicles working in wet conditions.
- Damage from driveline vibration that started somewhere else — a failing U-joint or an out-of-balance shaft will destroy a centre bearing, so find the cause.
ရာဘာအခုံ ဟောင်းနွမ်းခြင်း၊ bearing seal ပျက်၍ ရေဝင်ခြင်းတို့ကြောင့် ပျက်စီးသည်။
3. Telling It from a Universal Joint
Universal Joint နှင့် ခွဲခြားနည်း
| Symptom | Centre bearing | Universal joint |
|---|---|---|
| Vibration that increases with road speed | Yes — the strongest indicator | Sometimes, when badly worn |
| Clunk on take-up or when changing direction | Occasionally, duller | Yes — the classic symptom |
| Rumble or growl from under the middle of the vehicle | Yes | No |
| Movement when you lift the shaft at the bearing | Yes — up-and-down play at the support | No |
| Rust dust around the joint caps | No | Yes |
| Squeak at low speed | Possible if the bearing is dry | Possible if the joint is dry |
| မြန်မာ | အရှိန်နှင့်အတူ တုန်ခါမှု တိုးလာပါက center bearing | ဂီယာထည့်စဉ် အသံကျယ်ပါက U-joint |
Check with the vehicle safely supported and the transmission in neutral: grip the shaft next to the support and lift. Any vertical movement at the bearing is a replacement.
4. Why It Is Replaced with the U-Joints
U-Joint နှင့် အတူ လဲရခြင်း
- The shaft has to come out either way. Most of the cost is removing and refitting it.
- They have the same age and the same duty. A new centre bearing between two worn joints will be destroyed by their vibration.
- Vibration damages whichever part is left. The three components form one system.
- Check the shaft for balance weights and runout while it is out; a bent shaft will ruin new parts within weeks.
- Inspect the slip yoke splines at the same time — worn splines cause a vibration that no new bearing will cure.
Shaft ကို ဖြုတ်ရသည့် အလုပ်ဖြစ်၍ U-joint များနှင့် တစ်ပါတည်း လဲပါ — တစ်ခုခု ကျန်ခဲ့ပါက အသစ်ကိုပါ ပျက်စေမည်။
5. What to Record Before Ordering
မှာယူမီ မှတ်သားရမည့် အချက်များ
- Make, model, production year, and the chassis or load rating for commercial vehicles.
- Bearing inside diameter — it must match the shaft journal.
- Cushion outside diameter and overall width, measured on the old part.
- Bracket bolt spacing and whether the bracket is included.
- Whether the vehicle has one centre bearing or two — long-wheelbase trucks and buses often have two, and they are not always the same part.
- Any number stamped on the old bearing or cast into the bracket.
Bearing အတွင်းအချင်း၊ ရာဘာအခုံ အပြင်အချင်းနှင့် အကျယ်၊ bolt အကွာအဝေးကို တိုင်းတာပါ။ Center bearing နှစ်ခု ရှိ မရှိလည်း စစ်ပါ။
6. Fitting — Phasing and Preload
တပ်ဆင်ခြင်း — Phasing နှင့် ကြိုတင်ဖိအား
Mark the shaft before you separate it
A two-piece propeller shaft is balanced as an assembly and its two halves are phased — the joints at each end must stay in the same angular relationship. Reassembled one spline out, the shaft vibrates at every speed and no amount of balancing will fix it. Mark both halves across the joint before separating them.
Shaft နှစ်ပိုင်းကို ခွဲမီ အမှတ်အသား ပြုလုပ်ပါ — spline တစ်ချောင်း လွဲသွားပါက တုန်ခါမှု ဖြစ်ပြီး ပြင်၍ မရပါ။
- Do not tighten the support bolts with the shaft hanging. Set the vehicle at normal ride height so the rubber is not pre-loaded in the wrong direction.
- Check the shaft angle after fitting; the support position sets the working angle of both joints.
- Use new bolts or nuts where specified and torque them properly — a loose support hammers itself apart.
- Grease the slip yoke splines before reassembly.
- Road test at the speed where the vibration was worst, not just around the yard.
7. How to Order from Win Auto Parts
Win Auto Parts မှ မှာယူနည်း
Win Auto Parts stocks centre bearing supports, cushions and kits for the light commercial, truck and bus platforms common in Myanmar.
- Call 09 5105768 with the details from section 5.
- Or email support@winautoparts.com with a photograph of the old support in place, taken square-on.
- Or browse at winautoparts.com.
- Ask about the universal joints at the same time — they come out with the shaft.
- Bring the old support to South Dagon or Thakaytha for counter matching if the numbers are unreadable.
09 5105768 သို့ ဆက်သွယ်ပါ။ U-joint များကိုပါ တစ်ပါတည်း မေးမြန်းပါ။
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