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Gear noise in drivetrain

Blue71

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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 I’m 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? I’m 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
 

Broncobowsher

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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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Blue71

Blue71

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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

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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DirtDonk

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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
 

DirtDonk

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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.;):cool:;D

Paul
 
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Blue71

Blue71

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Paul,

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

Andy
Blue71
 

tasker

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Usually put a pint of simple green in the case too ;D
 

Rustytruck

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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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Blue71

Blue71

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Got the tranny out...hopefully going to inspect t things today. Keep ya posted.

Thanks,

Blue71
 
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Blue71

Blue71

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Got the tranny opened up today and to me.... the gears look great. I shifted through them 1,2,3,R and they shift well even with the detention spring pressed. There is a little end play on the input shaft but I’d say no more than an 1/8” or so.. is that normal? (The 3 speeds I have on the shelf seem the same). Maybe u guys can evaluate from my pics.
 

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Blue71

Blue71

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Here’s a few more
 

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DirtDonk

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...There is a little end play on the input shaft but I’d say no more than an 1/8” or so.. is that normal?

That's with the bearing retainer still in place, and just moving the end of the shaft side to side? If so, then yes that's pretty normal.
But it could still be at the ragged edge of normal, if the input bearing is the one making the noise.
Likely it's other bearings, but it can still be the input.

If you mean in and out movement, then I'd have to say no, that's nor normal.

I think the rear main output bearing is the one that takes more of the beating from what I've seen. But that seems strange and you'd think the front would share the abuse.
Lots of dynamics going on inside that little box though, so hard to say what's going to do what over decades of use.

But my own output bearing was toast at about 100k miles. Everything else looked great, but the rear grenaded when I did a hard reverse acceleration.

Paul
 

B RON CO

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Hi, take a close look at the rear bearing. To me it looks like it is not flush in the case, and maybe the inner race is crooked. Good luck
 

broncodriver99

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Do you have a pic of the tip of the input shaft? Did you check the pilot bearing/bushing? If the bushing gets a little worn it can allow the input shaft to droop a little and cause some harmonics. Usually if it is a needle bearing they are good until they fail completely.
 

Broncobowsher

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Yea, that looks pretty good inside.

I can see a little of the output shaft bearing. It looks from what I can see. Well at least the bearing cage is intact. Can you see any pitting in that bearing?

Next would be to pull the bearing retainer off the front and look at that bearing.

Was there any bits in the bottom of the case? Glitter?
 
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