Howdy, I'm rebuilding a '90 boss, and had some lingering questions. Now the previous owner had broke the chain while riding. Which caused a nice big hole in the tranny/gear box(I've seen and heard it called both) casing. I have a replacement tranny, so swapping isn't an issue.

My questions are this:
1, she needs a new rear sprocket, and I see that JT sprockets makes both a 42T and 30T. Is there a performance change with one over the other?

2, The replacement tranny/gear box has now oil in it and has been sitting for about 4 years dry. It spins good by hand, but I feel I should change the oil a few times in the summer to make sure that its clean and not chewing it self up, Is this a valid concern, and if so, what oil can I use besides the AGL from Polaris?

Thanks for any help in advance.

 

Going from a stock 38 tooth rear to a 42 will give you more low end grunt,will loose some top end speed. Wouldn't recommend a 30 unless you plan on using it like a golf cart.
Polaris AGL only is what I'd use,unless you can find oil designated for chain driven gear cases.

 

1. The difference in sprockets is that one is going to give you a higher top speed (30T) and one will give you better acceleration (42T). Which one you choose depends on your riding style and where you ride.
2. The transmission should be fine, I would strongly recommend using Polaris lubricants since they are recommended (though not cost effective) and believe that Polaris AGL is around 75/90w but I am not sure and I would hate for you to grenade your transmission because of something I posted.

 

AGL is way thinner than 75/90 wt. Too thick of an oil and the splash plate in the gear case can't throw a good enough spray of oil to keep the chain and bearings lubed up.

 

Ah, thanks for the advice.
And AGL sounds closer to auto transmission fluid than gear oil

 

It's a little thicker than atf.

 

Ah, good to know