When did you have you're drives done by MMW?
It is strange they didn't use XR gears unless there is a reason for not putting them in a Bravo 1 case.
The early IMCO's had alot of failures if you read the posts on here.

I'm working on designing a new upper gear set for an XR drive.

Should know more in a few weeks.

Straight or spiral?

Well hurry up & I'll test them to destruction.

They will be the straight gears as used in the XR drives, but hopefully will hold up to at least 800 hp.

And I will be testing them personally with a big heavy boat and 800 hp and 900 ft lbs

Smitty,the current XR gears are forged? and made from what sort of metal?
Is/will a billet gear be stronger?
Who do you think in your opinion makes or modifies the best currently available gears?
Does getting "more tooth contact"like the bravo 1 spiral gears as oppose to the XR style help?
I just wonder if the Bravo 1 failures related to HP are attributed to the gears or is it the towers,shafts etc letting them down whereas if a reg Bravo1 was given all the upgrades the XR gets with a huge set of spiral gears.

My biggest challenge is to get a stronger gear in the same space as the current gear occupies.

Helical gears would be stronger, but the teeth are to narrow now and there is no room to get bigger.

The current rash of failures are due to the quality of the metal used in the gears along with the fact that they are 2 piece gears. That hub that holds the brass ring is welded on.

Billet gears might be stronger but they cannot be CNC'd right now because of the hub.

That's all I can say for now. I am on a mission to get something made that will hold 800 hp and last more than a season !!!

Go Smitty... GO!!

If you can get this project accomplished...
you will sell a ton of them.

Chris

Not Smitty but I'll have a shot at answering.
Replies above in red.

Also in the report I commissioned, FWIW,

Comments on

"Material Identification of Damaged Bevel Gears'

'Two damaged gears, one a straight bevel gear and the other a helical bevel gear..were submitted for metallurgical examination primarily for material identification purposes.'

'Metallurgial examination has revealed that the bevel gears had both been manufactured from a low alloy case-carburising steel....
Cross-sections of teeth taken from each gear showed that they had been case hardened to an approximate effective case depth of 1.1mm,ie minimum case depth at which the hardness remains above 500HV. Both the material and heat treatment, including the case, is considered satisfactory for this application and not likely to have been contributory in failure.'

Steve

To answer the OP question,
Year 2000, serial # OM100000 and above was when the X, XZ and XR were introduced.
So a 1998 model would have the old style gears, ie, helical bevel, thinner floor, different bearings and small U-Joint yoke, unless, of course, it has been upgraded.

Steve