Help troubleshooting big bang!!

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Silveredition

Silveredition

10 Year
Joined
Jun 24, 2014
Threads
79
Messages
747
Location
Western Australia
Gday all, I am hoping someone can help troubleshooting an issue I had today… so, I got home from work and got a call from my wife (who was walking along the beach), to ask me to drive down as a family was bogged and needed help to get out… I let the tyres down and drove down and along the beach to where they were….. I had to turn around a little bit away from them as there was a slope that I didn’t want to get caught on… I turned down the beach, put it in reverse, and gave it a fair bit of throttle to reverse back up into the track… there was a very loud ‘bang’, then no reverse drive!! I said to my daughter - I think I have just done a rear diff!! I then engaged first, and it drove perfectly! Another reverse, and the same bang! As well as clutch smell - wasn’t riding the clutch at all!! I now drove forward and back into the track (lots of throttle!!), then reversed in the track to where I eventually snatched the bogged car out…
When I got home, I checked the drive shaft for play - all good, clutch works perfectly, nothing abnormal!… I have only a few days ago replaced the clutch master and booster, but can’t work out what would make a sound so loud and disabling to stop drive (in reverse - momentarily!!)
I know there are a lot of very knowledgeable people on here, who I would love to have a think and give me their thoughts…
A bit of info…
12ht - 5 speed manual
GTurbo / PDI etc (rebuilt engine and mods)
Torsen rear diff with solid spacer
New uni in rear of driveshaft
Newish Fri t prop shaft
Newish (125000km) gearbox built for the extra engine power
Had Exedy clutch ( 150000km old - but never an issue)
Please help!!
 
Hard gas while cranked, in reverse=birf :nuke:
 
Birf/Hub or reverse gear in the transmission - done the last one more times than I'd care to admit with a powered up 1HD-T and R151
 
Was thinking (at about 2:30 this morning!!) could it have been the clutch letting go, then slipping momentarily? Seems to be the only thing I can think of that would have clutch smell, and drive perfectly straight afterwards… too much torque for it in reverse when revving hard in really soft sand??
Will see how it drives to work today…
 
I think both times you did not have the transmission fully in reverse, then when tension was applied the gears slipped apart under force resulting the bang. I've had this happen a couple of times when in first gear.
 
Thanks for all of the suggestions as to what it might have been!
Since the 2 big bangs, I drove a couple of km along a soft beach, did 100m or so in reverse on the soft beach, snatched a bogged car out (snapped the snatch strap on the first attempt), driven It daily to work and back on the highway at 100-110km/hr… without a single odd sound!!
Still very confused!! I have a fair bit of beach driving over the next few days, so will see what happens!
 
From my gut feeling something went out of engagement - most likely a dog clutch engaged gear like the reverse or transfer high/low gears. This will create a nice bang.... Has the gear or transfer lever not moved into neutral ?
The detent mechanism will try to hold it in place but especially with high rev's and torque it could slip out if the dogs are not perfect. Next time it could just hold fine because there is just that tiny amount less torque / torsional oscillation due to different soil/sand conditions.
That is not a clutch issue.
I had something like that years ago with a foulty free wheel hub - in deep sand and high torque scenarios the dog clutch would -!BANG!- slip one teeth -
re-engage then do it again in something like 50 metres or yards if the conditions stayed the same. But that of course affected only one front wheel. The BANG was still impressive.
 
Thanks again everyone! About 100km of soft beach driving and 100km towing the boat on the highway over the weekend and no silly noises… I didn’t give it heaps in reverse on the beach to test it though… Will leave that one for when I don’t have a big trip coming up…
 
My bet is on Jim’s post # 7. @Godwin
 
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