8.5 or 10.5 in classic Ultima? Or too much???

[Boons]

Hi all,

I'm going to be running my Ultima with a shorty length ways inside the chassis with a modern brushless set up. As there is no slipper I'm concerned my motor choice will be too much for the light front end. I'm hoping the transmission holds out too! I seem to recall the ball diffs fitted to later Ultima's weren't very good? Could this 'act' as a slipper, or would that just wear the diff out?

Sorry for all the questions!

Cheers
Ryan

[DrPaul]

I run a number of vintage Ultimas. From your question im guessing you want to run your Ultima against modern cars, the Mk1 Ultima is not a competitive car anymore, it doesn't have a slipper and the gear box will not survive fast brushless motors. A 21.5 or 17.5 would suit the Mk1 and make it drivable. in a vintage class with the right motor it can hold its own. I've taken my brushless out now and run 27T stock brushed, geared correctly its fast enough down the straight and smooth through the infield. If you run brushless u want to run 32dp gears as they are much stronger than the 48dp hop ups of the time.

you can check out one of my Mk1's in the vintage section.

Good luck.

[terry.sc]

The gearbox is pretty bulletproof, I regularly bash with my Ultima using a 13 turn brushed motor in it, and the same gears in my basher Optima as well and both get plenty of abuse.

Your main problem with a high power motor is keeping the front end down and getting any steering on throttle. The ball diff can't be used as a slipper, there are no replaceable diff washers in it so if it slipped you would need new hard to find diff parts very quickly. You could try the OT-74 Limiter Gear Set from the Turbo Optima, but that is designed to absorb shock loads on the transmission, for example on landing from jumps, than something that is designed to limit the torque through the transmission.

[Boons]

Cheers guys.

Maybe I should just stick a modern buggy rear end on it with an out back motor

[DrPaul]

"Your main problem with a high power motor is keeping the front end down and getting any steering on throttle. The ball diff can't be used as a slipper, there are no replaceable diff washers in it so if it slipped you would need new hard to find diff parts very quickly."

Terry is 100% right, with that power brushless, the car will spend more time wheelying and have zero on throttle steering. If you check out my pictures running a shorty lengthways and with a bunch of lead towards the fron of the car plus a geared correctly not to powerful motor, the car will have plenty of balance and on throttle steering without popping a wheelie every time I hit the throttle.

[DrPaul]

Originally Posted by Boons

Cheers guys.

Maybe I should just stick a modern buggy rear end on it with an out back motor

Its not an Ultima then though

If you dont want it as an Ultima why dont you just save a bunch of money and buy a modern buggy which performs 100% better??

[Boons]

Originally Posted by DrPaul

Its not an Ultima then though

If you dont want it as an Ultima why dont you just save a bunch of money and buy a modern buggy which performs 100% better??

Only kidding mate.

I have modern stuff, just liked the idea of a fast ultima really. I started racing with one 25 years ago.