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Mysterious grinding [ouch] noise on BN2

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bighealeysource

bighealeysource

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Hey y'all.
Drove up to the Carolina British Classic car show in Columbia, SC yesterday, about a 3 hour drive from my home in Beaufort, SC. About an hour into the trip on I-95 after averaging about 75 mph the entire way in a 3 LBC caravan, decided to get off and take a back road due to the interstate backing up with Spring Break traffic going home. Anyway, went down the exit ramp and as shifted into 3rd gear, got a very momentary grinding noise from the rear end, almost locking up, and then it was gone. Pulled away from the bottom of the ramp to get out of the way and got another very quick grinding noise and then everything was perfect. Stopped, got under as much as possible, no gear oil leaking from anything, nothing on wheels to indicate a bad oil seal, and decided to continue on. Did have the infamous 90 wt gear oil smell for a bit, but it too went away quickly. Got to the show about 2 hours later after taking back roads and no further noises, smells, etc. Everything ran fine, tranny shifted fine, nothing from rear end. Attended the show, checked the car again, still everything was fine. Drove home on the Interstate entire way, averaging at least 70 mph and 100M ran great. Got it up in the air this morning, checked dizzy gear oil, and it dribbled out as expected when took out the plug, smelled normal, but did notice some gear oil on the back frame rail, just behind dizzy. Have NO IDEA what happened and no indication of where it might have leaked or anything. Any ideas ????
Thanks,
Mike
 
What do you mean almost locking up? Sounds like maybe you have a broken piece of something floating around in the case. Maybe a piece of gear tooth?
 
Hey Richard,
Double ouch ! Yeah, it happened so quick when I was slowing down and then down shifted from 4th to 3rd but did feel like the rear wheels locked up just momentarily. This was after the awful grinding noise so might make sense a gear tooth broke off somehow. Was not a violent downshift or hard downshift, just nice gradual with no strain on trans or engine. Then as I mentioned, got another quick grinding noise after I pulled away from the stop sign and now everything "seems" fine. The fact it was on a downshift, maybe it actually came from the transmission but manifested itself with the rear wheels locking up if a tooth literally stopped everything from moving? I would think a gear tooth would fall into the bottom of the case and that would be the reason it no longer interfered with other moving parts. Have not noticed any other louder gear noise from the trans and drove perfect on way back. If it is the trans why would I get the gear oil smell which is only in the diff and a small amount as leakage? If you're out there Randy F, chime in as you're the transmission guru !!! Regardless, none of this sounds good.
Thanks
Mike
 
Mike-

How often do you put your nose near the differential and NOT get the (in)famous 90wt gear oil smell?! This might just have been a coincidence. My bet's on a broken tooth in the gearbox. Unfortunately, unless you can get the tooth out of the case more damage can result.
 
Well, drain the trans oil next and investigate that. Get a flexible wand magnet and probe around inside to see if you can find a chunk of gear tooth. It could help eliminate that as a problem if nothing else.
Jim
 
One advantage of the BN2 trans is you can remove the entire side cover without - I THINK - removing the entire trans. If I'm wrong someone please tell me ! Thinking if I do that would be able to inspect the innards and see if there is a broken tooth or teeth and hopefully find them in the bottom of the case. Took it out again today and no noises or gear noises and shifts great, no problem with gear selection or anything. Hoping someone will tell me the broken tooth has most likely fallen into the bottom of the case and will remain there for eternity and I do not have to get it out !!! Let's hope !
Thanks,
Mike
 
Well another update - drained the trans/OD oil and did find minute metal pieces in it, size of a bent of staple and very small bits, by passing a magnet through the oil. So, could have been there forever or an addition from my gear crunch this past weekend. Trans is shifting perfectly, no gear noise or grinding, so guess have to assume it was a broken tooth and the second crunch turned it into pieces small enough to flush through the oil. Going to follow the ancient advice of many car guys "if it aint broke don't fix it" and since it aint broke, going to leave it alone for now. Have spoken to Randy Forbes about working on the tranny for me some day so will just keep that thought in mind and be vigilant.
Regards,
Mike
 
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