1G replacing oil pump straight gears with helical

[dwb]

I have an early 6bolt with original straight cut oil pump gears. Since those gears are discontinued, can I swap directly to the helical gears or do I have to replace the front case along with the gears?

 

[DSSA]

Here's the TSB for anyone interested in reviewing it:

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[Mech Addict]

Must have been some rather timid drivers to hear the whine from those little gears. When I drive my car it makes a nice snarl starting around 2,500 rpm, and by 4k it’s yelling. I can hear a turbo whoosh at times, too, but not sure I’ve ever noticed gear whine, let alone been bothered by it. Must have been drivers that bought them for style over performance.

 

[pauleyman]

Must have been some rather timid drivers to hear the whine from those little gears. When I drive my car it makes a nice snarl starting around 2,500 rpm, and by 4k it’s yelling. I can hear a turbo whoosh at times, too, but not sure I’ve ever noticed gear whine, let alone been bothered by it. Must have been drivers that bought them for style over performance.

You would be surprised. I'm a lifelong car guy and this was when the car was only 2 years old in 1992 with 35k on it. I know what gear whine sounds like. It was weird and unexpected. Now I wouldn't care but at the time it wasn't "normal".

 

[steve]

I didn't notice the noise or maybe mine was quiet. It just magicly got replaced during one of the normal visits to the service department. I was on really good terms with the Service Manager from day 1 so he would call and say to bring the car in when there was a new TSB.

The car originally was pretty quiet even at WOT not like the tin can it became.