Massive bang on quick gear change

[Error404]

Taken my car for a shakedown run before MOT next week and really pissed off TBH!

Every single bush and mount on the car is new and i'm getting a massive bang in the rear from the transmission / rear diff on quick gear changes, seems worse than before I replaced all the worn items

New parts on the car:

new 034 street density engine mounts
new OEM gearbox mounts
new OEM diff mounts
new powerflex rear diff mount
new SQ snub mount (oem rubber - going to try one of the stiffer replacements)

WTF is going on?

[Kieron20V]

Same as my CQ was after I tightened everything down. Seems to be play in the driveshaft CV joints or support bearing. Taking all the slack out of everything else just seems to make it more pronounced. Bit annoying eh?

[lind4hl]

you have a coupé right??

[Error404]

yeah proper pissed off mate
Can't get my head around the CVs causing this though - I cleaned them all out and regreased them before i built up the S2 rear driveshafts and measured the balls and housing against a brand new inner joint I have and there was no wear on them at all.
I thought it was maybe the diff itself, or where I have a cracked gearbox mount or something else unnoticed

yeah its a coupe Alex

[lind4hl]

hmm, dont know then.. avants could be front diffmount,

but change gearboxmounts to same stiffness as engine if gearbox can move more than engine it could crack the bellhousing...

[Rusty]

I get a bang on gear change, it's a backfire reverberating through the stripped cabin

Also think the prop bearing needs sorting, get some shunt on gear selection at standstill.

[Rusty]

I get a bang on gear change, it's a backfire reverberating through the stripped cabin

Also think the prop bearing needs sorting, get some shunt on gear selection at standstill.

[Error404]

would be a good excuse to fit my CGR box then but I have 034 street density so only about 10% stiffer than standard


EDIT: Andy I did wonder if its amplified as i have zero interior or sound proofing etc in the car at the moment...

[lind4hl]

would be a good excuse to fit my CGR box then but I have 034 street density so only about 10% stiffer than standard

then probably OK!

[quattrostyle]

maybe too much play on the rear diff.?

[Error404]

hmm hope not

[Rusty]

Want to try a solid snub mount?

[Error404]

well i've got a SQ on at the moment, but on the stock rubber mount, so was planning on trying one of the stuffer rubbers that Paul found.
You got one i can try then?

[Error404]

does anyone have any info on the factory spec for rotational play in the rear diff? i.e. how much free rotation there should be on the output flanges?
I never checked the diff backlash when i fitted the V8 diff but there was no need for shims so I assumed it was ok
Wondering if theres too much backlash... really hope I don't have to take it off again

[LVrainman]

a bang in rear diff which comes up after a quick/sporty gear shift can be caused either by dead rear diff bushing or worn rear diff "cogwheels" or "gearwheels". dont know the exact name ...