Automatic Trans Speed Upgrades

I’ve got an older Murray with an Automatic transmission and a 24 Intel V-twin I’ve swapped in to build a racing mower. It’s got a 6 IN pulley off the crank and what looks like a 3 IN pulley on the trans and It still has all the tensioner pulleys. I read on Google it’s more difficult to get one of those transmissions to get going faster than a Manual (which makes sense to me) and I was curious to see what people have done here to make them get going faster.
Before I put a different pulley on it it went maybe 3 MPH and now with a complete guess I’d say it’s closer to 10 MPH.
If you have any suggestions/info for me it’s all greatly appreciated!!

Hydrostatic (automatic) transmissions produce more fluid bypass internally and fluid aeration when pully input shaft Rpm goes higher.

The design of the hydrostatic transmission does not have any internal tricks to really make it go much faster.

If you want more actual speed, find an early manual shift transmission and experiment with input pulley sizing that way. You can pull wheelies with the right pulley combination.

The basic manual forward and reverse only transmissions are a lot of fun. The multiple forward speed versions tend to break the gears because they are narrower/ compact by design.

It's been many years since I played around with "racing mowers". Back then most riders had manual gear selector transmission except for the friction disc drive models

And beside that Murray probably has Tecumseh hydro transaxle which is iffy at it best and there is no repair parts for it. So if you break it, it be all she wrote.

As I recall Peerless made quite a number of rider mower manual gear drive transmissions. Many of them were used in MTD and AYP chassis riders. "Murray" is just a chassis product label.

The only weak point was the input shaft and pulley shearing the splines or keyway, but a tack weld can resolve that after you find the pulley size you want for your top speed goal.

Yes Tecumseh Peerless and Dana made a lot multi speed manual transaxles. But people got so lazy they couldn't shift the lever so Hydros came out.

Now the Peerless and Dana does also another weak spot that is the input shaft needles bearings.

Now people are getting so lazy that type can't even turn a key to start a mower.

Auto Doc's said:

As I recall Peerless made quite a number of rider mower manual gear drive transmissions. Many of them were used in MTD and AYP chassis riders. "Murray" is just a chassis product label.

The only weak point was the input shaft and pulley shearing the splines or keyway, but a tack weld can resolve that after you find the pulley size you want for your top speed goal.

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Peerless is the best bet.