gsd2000

iTrader: (1)

I just wanted some general input as to why people think my gearbox went bang.

I took it drag racing, it was a standing mile event and as i was slowing down i pulled the car out of gear and went to downshift from 5th to 4th, i had just braked from around 150 mph to around 40mph.

The gearbox then wouldn't go into gear, i thought i got it into 5th but as soon as i lifted the clutch the gearbox would grind.

Here are some photos of the damage, but i can't quite understand the cause of it, i just want to try and prevent this from happening again.













The damaged components include:[/LIST]
Reverse Gear
2nd Gear
3rd Gear
6th Gear
5/6 Synchro
1/2 Synchro
Countershaft
Countershaft Extension
Also the damaged bearing
[/LIST]
The gearbox oil was Royal Purple Synchromesh, it wasnt leaking but i stupidly never checked it before the event.

The car is a Vauxhall Monaro with an MM6 T56.

Thankyou

thesource

iTrader: (60)

Thats a good one...... this is the main reason Tremec installed a 1 piece counter shaft in the later model Viper and C6 units.

bearcatt

iTrader: (41)

That's some major carnage right there.

5th and 6th are mainly overdrive gears but I also have reservations about Royal Purple.



.

fleetmgr

Looks like a lack of lubrication to me.

jmd

iTrader: (4)

Possibly improper preload of the extension shaft.

gsd2000

iTrader: (1)

Is the best oil to use?

I get the impression that some people do not like royle purple, why is this? Is royal purple really bad for t56's?

SuperSport01

The best oil to use is the OEM fluid.

thesource

iTrader: (60)

Royal Purple didn't do that. 5th gear and 6th gear are not really designed to be a performance gear. They are economy gears only. When you put the unit into 5th gear you are applying a hell of a lot of load on it. The area where the extension shaft meets the cluster gear is taking alot of pressure. I've seen several units come in with stripped out lugs on the cluster gear or extension shaft.

gsd2000

iTrader: (1)

so a one piece countershaft is a must then for a car that does standing mile events?

thesource

iTrader: (60)

Yeah I would suggest it if you plan on doing this kind of racing. Is this unit a 2.97 ratio or 2.66 ratio unit?

gsd2000

iTrader: (1)

2.66

my plan is to use a used 2.97 ratio t56 out of another monaro and then over the next 12 months rebuild this and make it good and strong