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SM465 grinds in cruise mode - audio attached

RootBreaker

RootBreaker

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so I have been noticing a problem with a weird sound.. so I drained the trans and added new gear oil. and it is not better... so full rebuild.. I know... I know.. or ZF56 would make me a happy man.. but they have a thin shaft at 6th gear.. I'm thinking of rebuilding this one to accommodate a 8.1L...

but humor me with what you think this is.. I'm driving it but don't want to be left on the side of the road...


 
Hard to tell, does the grind change based on engine speed or ground speed?
 
Was that just in neutral? Or were you pressing the clutch at all during that video? I've had a throw out bearing make noise similar to that when idling in neutral. Press the clutch in it went away.
 
Sure its coming from the transmission ?...not the T-case or rear end ?..

Rear diffs can grind on coast or when de-accelerating if the pinion bearings are loose--I had a '69 Cougar that made horrible grinding noises when you let off the gas ,and I found out the pinion yoke nut had loosened up..tightening it eliminated the noise and grinding..sounded a lot like a u-joint with too much shaft angle that was worn out on a lifted 4x4..
 
well all good points.. ill check into them.

now..
ujoint - not sure
neutral - no but also doesnt do it on acceleration only on coasting with foot off gas and in gear
neutral - with clutch in it doesnt do it.. would it matter if i put in neutral and let clutch out? would pilot bearing still be used at that point? (sorry dumb q there)
rear diff - well I did put the detroit in LOL... never did gears before but used the old gears...

weird thing is it makes totally different noises at different times.. chatters, clatters, grinding, etc... i know tough to tell from that..

so I am thinking rebuild on both trans and xfer.. especially if im thinking an 8.1L in front of them!!!
 
An 8.1 will certainly make quick work of determining which part is faulty...:thinking:...

The pilot bushing only comes into play when your in gear at a stop with the clutch depressed..the main shaft on the trans isnt turning,the engine is..that is when you'd hear the most noises if it were faulty--the newer needle bearings ones dont seem to last,and when they start failing it can make it hard to shift,because it tries to keep the main shaft spinning instead of letting it free wheel..

I'd get someone to sit in the truck and run it through the gears where it makes the most noises,and get under it (carefully!) and listen to the rear diff,the transfer case and tranny,and see if you can determine which one its coming from--a sounding bar or stethascope might be useful here...unfortunately the driveshaft can act as a amplifier and make it sound like its coming from somewhere else..
 
Did I miss something? All this talk about axles, u-joints and Detroits but the video I watched shows the truck sitting still in the driveway with the tires on the ground and nothing moving? Can we not infer from the video posted that this noise (in the video) has to come FROM THE TRANS IN NEUTRAL or THE TRANS IN GEAR WITH THE T-CASE IN NEUTRAL (taking the axle and u-joints out of the equation)? If so, -- again -- clutch in or out in the video?

:dunno:
 
nvrenuf said:
Did I miss something? All this talk about axles, u-joints and Detroits but the video I watched shows the truck sitting still in the driveway with the tires on the ground and nothing moving? Can we not infer from the video posted that this noise (in the video) has to come FROM THE TRANS IN NEUTRAL or THE TRANS IN GEAR WITH THE T-CASE IN NEUTRAL (taking the axle and u-joints out of the equation)? If so, -- again -- clutch in or out in the video?

:dunno:
Click to expand...


hahahahaha... that pic was just a placement... youtube doesnt let you upload audio only.. so i took a pic and placed audio to it.. so it would go to youtube
 
Ok, I guess that's easier to see on a PC than a phone.
 
It does sound like a throwout bearing to Me as well. Or possible front main bearing if the trans isn't aligned and clutch if off or worn. I had my bellhousing crack and didn't know it and it ended up wearing out my front main bearing from tortional stress.
 
RootBreaker said:
well not sure if you saw my other thread.. but im hoping it is actually this and dont need to rebuild trans... well shifter wobbles a lot thus most likely rear trans bearing but doesnt leak...

guess lets get this fixed first to decide...

1978 r&p vs detroit locker by
Jeffrey Riggs, on Flickr
Click to expand...
That's no good either. I guess if fix that first then go from there.
 
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