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Old 05/17/18, 08:33 PM   #1
Blue71
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Gear noise in drivetrain

i got a 69 Bronco 3 on tree, 302 running and driving that had sat for 26 years(1992). It drives really well other than clutch chatter. I have drivetrain/ gear whine in 1st and 2nd gears- but 3rd gear is normal with little to no noise at all. It sounds like Im driving in 4wd in 1st and 2nd, but I checked and shifter is in 2H, front driveshaft rotates freely by hand , hubs are unlocked and front axles rotate freely by hand as well. I changed all of the fluids before running and driving. All fluids were surprisingly new looking and all gear oil levels were full. Any idea what would cause this gear drivetrain noise? Im getting ready to put a new clutch in it so the tranny will be out...is there anything I should check ? Input bearing, etc?

Thanks,

Blue71

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Old 05/17/18, 08:40 PM   #2
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Input shaft bearing in the transmission. My guess anyway. Usually but not always.

In 3rd gear (for the 3-speed) it is 1:1 direct pass through. The gears and bearings are not loaded in 3rd gear. So it is quiet in 3rd.

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Old 05/17/18, 10:02 PM   #3
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Thanks Broncobowsher....I’m putting that on my list to replace as we do the clutch next week. Is there just a bearing there? Does it have a race, seal, etc?

Thanks for the info.

Andy
Blue71

Quote:
Originally Posted by Broncobowsher View Post
Input shaft bearing in the transmission. My guess anyway. Usually but not always.

In 3rd gear (for the 3-speed) it is 1:1 direct pass through. The gears and bearings are not loaded in 3rd gear. So it is quiet in 3rd.

Last edited by Blue71; 05/18/18 at 05:31 AM..

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Old 05/17/18, 11:43 PM   #4
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The main input and output bearings are caged roller bearings. One piece and not usually pressed on tight. It's a tight fit, but Iv'e pulled and replaced them without resorting to pullers or presses.
I can't remember if the front has a lock ring on it that needs to be pulled to get it off the shaft, but the main retention is the "bearing retainer" which doubles as the shaft on which the throwout bearing slides. You've seen that part no doubt. Has four bolts and usually a gasket. Has a drainback notch in it that faces down.

It's possible that the loose roller bearings that fit at the interface between the input and output shafts, literally in the middle of the transmission, could make the noise as well. But that's a much bigger job obviously.
Once you have the box out and on the ground, if you do go that far, you should be able to feel if other things are not kosher.

That said, if you decide to pull the whole trans rather than do it in the vehicle, be aware that if you separate the intermediate housing from the back of the transmission, you need to lock the shift levers in place (first gear maybe? I don't remember) to keep the output shaft from pulling out too far and literally dropping those loose rollers into the bottom of the case.
It's a small task, but one that often gets overlooked and leads to a full tranny tear-down to put the bearings back in.
Have fun!

Paul

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Old 05/17/18, 11:47 PM   #5
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Oh, and while you're in the front of the thing, might as well change the shaft seal as well.
Part number of the front bearing "should be" a 208L.
Rear bearing "should be" a 207L
And the seal "should be" a 47499

I say "should" because I'm only 99% sure I'm right on that.

Paul

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'68 LUBR, 2.5 + 1 WH, 31x10.50, 4.56, Explorer and 4R70w by EFI Guy, WH disc brakes, Hanson front bumper, Warn winch. "Bought, not built"

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Old 05/18/18, 05:34 AM   #6
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Paul,

Thanks a bunch for the great info. Will keep ya posted on my slow progress

Andy
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Old 05/18/18, 05:48 AM   #7
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Usually put a pint of simple green in the case too

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Old 05/18/18, 01:05 PM   #8
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Pull the drive shaft and drive it on the front. That may isolate a rear drive issue. Make sure your transfer case shifter and linkage isnt rubbing on anything carrying sound up the shaft. I had an issue with a jshift once sending noise up the shaft.

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