WTB 901 transmission "H" gear set, And 904 main shaft Options

[Driver174]

As title states I am wanting a "H" gear set for my race car.

Jim

[mlindner]

Have you checked with Dr. Evil.

[Steve]

https://www.cogscogs.com/Transmission-914-M...Speed_c_92.html
I bought my H gear from these guys, but check with Dr. Evil First. Dr. Evil also set me up with a taller 3rd and 4th to match the H fifth for my SBC conversion. The gears feel like a stock transmission, roughly 1500 rpm's between gears.

[Chris914n6]

'H' gear is used by v8 swappers as a high 5th gear for cruising. It's gotten hard to source now as it was only used on 911 4 speeds.

I don't think you want the tall OD gear for racing so it would be cheaper & easier to pick a different gear set.

[Driver174]

H gear set will be taller 2nd gear for slow rolling starts. The last time I used 2nd during a race start, I spun the engine really high. I was on pole and slowed everyone down. It work out well for me but I’m thinking a taller gear will work better.

[Steve]

H gear set will be taller 2nd gear for slow rolling starts. The last time I used 2nd during a race start, I spun the engine really high. I was on pole and slowed everyone down. It work out well for me but I’m thinking a taller gear will work better.

You do know that a 914 trans has a fixed 2nd gear and can't be changed. You would have to replace the 914 mainshaft with a 904 mainshaft which allows you to change 2nd gear.

[Driver174]

You are correct Steve; I forgot about that. I guess I need a 904 main shaft as well.

[brant]

I think…. But do not know for certain as I have not tried an H gear

That h will not fit inside the case in 2nd possibly

My 2nd is J
I assume slightly larger than H

And the case had to be machined inside to make the room
Plus. The machining opened a window in the case
Causing the window to have to be welded closed
And you have to remove reverse to create the space for the width of the gear. Plus the 904 main shaft

So it all turns into a 10K transmission when your done with rebuild and cooling

Not a bolt in job by any means

I haven’t tried H though

But I run F J O S V

[sixnotfour]

G-box in Erie Co. has a bunch of ratios..

[stownsen914]

There are a couple options to do what you want to do:
- H on a 904 mainshaft as suggested. Great option. 904 mainshafts are pricy, and the gearsets are unique to them, i.e. a regular H from a 4 speed won't fit a 904 shaft.
- You can also have a stock F mainshaft turnd down and an H welded onto it (and the other gear just goes into place on the pinion shaft, no mods). I have a "KA" second (stock 914 5th gear ZD flipped and welded to a stock shaft in the second gear position. I've run this for years, no machining was needed to the case.
- Consider a GA second. This was a stock gear on 70-71 911s, so much more plentiful than a 904 shaft, and almost as tall as an H. Might be worth checking a gear chart to see if it could work for you.

[Driver174]

There are a couple options to do what you want to do:
- H on a 904 mainshaft as suggested. Great option. 904 mainshafts are pricy, and the gearsets are unique to them, i.e. a regular H from a 4 speed won't fit a 904 shaft.
- You can also have a stock F mainshaft turnd down and an H welded onto it (and the other gear just goes into place on the pinion shaft, no mods). I have a "KA" second (stock 914 5th gear ZD flipped and welded to a stock shaft in the second gear position. I've run this for years, no machining was needed to the case.
- Consider a GA second. This was a stock gear on 70-71 911s, so much more plentiful than a 904 shaft, and almost as tall as an H. Might be worth checking a gear chart to see if it could work for you.

Does the GA ratio utilizes the same 18 tooth main shaft gear and just a 32 tooth gear is needed? If that is the case then it looks to be my best option.

[brant]

GA main shaft is a full shaft replacement(two gears)
It is also a fixed gear main shaft but a different ratio than the stock F

They are much cheaper than a 904-main

Probably around 500$ these days

[GregAmy]

I'm running A-H-N-U-ZA on my four-banger historics car. Seems to work well for me.

I did not use a 904 shaft. Instead, a known shop* lathed the F gear off my 901 shaft and hand-cut the splines on the shaft to make the gear fit.

Welding would work, too, but that negates my ability to easily swap gears in the future. And would it need to be heat-treated?

GA

*I'm only offering this to demonstrate that it can be done. I hesitate to offer the name as I don't know if he'd want to get asked by others for that service, it took a lot of his time.

[stownsen914]

Exactly my point about the GA, it's a cheaper option since it was a stock production ratio. Agreed you should be able to find a good one for a few hundred $.

For the welding option ... technically the shaft and gear should probably be annealed before welding and then heat treated afterward. Not sure what specs though, you might be able to get the info though. I'd worry about deforming the shaft during whatever quench phase would need to be done and winding up with runout in the shaft. I've known a number of people who have welded gears to 901 mainshafts, and when I inquired about heat treating, all of them said to not worry about it - just weld it and be done. I've run a welded shaft behind 250 hp for years without issue.