Most liked posts in thread: Sprite Race Gearbox Rebuild

Ran into a snag on this gearbox.....turns out it may be either a Morris Minor box or has the guts out of a smooth case Sprite box in it. The mainshafts are completely different, and the gears are smaller too - probably why it broke.

So, we're stopped for a while.

Clancy says he has three "cores" in his garage and we can get what we need from one of them or simply rebuild one of them for Bugeye Dave's car, but he's out of town till Monday or Tuesday.....

In the first pic you can see the pin I have to push in, so I can rotate the plate with the tiny hole it it till the splines line up, then I have to carefully lift that plate while not shooting the pin out from under it off into outer space. Once that's all out I can slide the gear off the roller bearings.......except this one has brass bushings! RuhRoh!





Then when I compare the gears the inner diameter on the bad gear it's quite a bit smaller than the new ones - that are made to run on roller bearings. So - we need a completely different mainshaft - I'm hoping the case is the same for either one - and I think it is. Anyway you cut it I get to strip down another gearbox......

Wait till you see the fun shenigans I get to have to get 2nd gear off the mainshaft - there are two pins, a top plate and two small plates under that! See the last pic.....

 

Delivering this box to the owner Wed AM, we're all going up to Jesse Prather Racing to put the white race car that I built the engine for on his dyno and see if we can get the last bit of power out of it - even tho it runs really well right now there might be a bit more left. We're also going to put a Bugeye on that I built a 1275 engine for last year and a Morris Minor pickup that belongs to a friend of mine.

The Bugeye has a Weber on it - he just hasn't been able to find someone who knows what they're doing to tune it properly. Jesse and Kent Prather are both really sharp on Webers, they should be able to get it shaped up.

The Mo has a 1275 too, but he's running an SU HIF44. I have a few needles for it but not many, we should be able to get it close tho.

Going to be a fun morning. The race car is leaving for the race at Grattan in Michigan as soon as we're done on the dyno.

Going to be a hot day tomorrow so we're getting an early start, first runs are at 8 am.

 

The next step in this build is to clean and tap all the threaded holes - I remove all the studs to make it easier to clean the gasket surfaces, and in this case the studs were also coated with gasket sealer and rust. I think this gearbox either sat outside or in a humid garage for quite a while as there was rust in some very strange places.

So with the case all cleaned up I found there was a broken bolt - never fun to get out of an aluminum case. It's very easy to drill off center and tear up the aluminum and not get all the steel out.....this was one severely corroded in place.



To start with I used a small file to try and flatten the broken end as much as possible, but it was below the surface of the case, so all I accomplished was to take a nib off the end. Next I carefully center punched the end of the bolt, then got out one of the best tools I've ever owned, a set of left handed drill bits. I didn't think this one would wind itself out, but you never can tell. I used a small bit to carefully drill a pilot hole and it was centered nicely. Next I went after it with a finish bit and as you can see by the pic, I got out a lot of rust along with the steel. Once the hole was done I picked out what threads I could, then used the correct tap to clean up the rest of the threads. It came out nicely!







I also cleaned up all the rest of the bits and pieces, and put the mainshaft together.....as always, installing the pin keepers on 2nd and third gears is always the hardest part of putting the mainshaft back together, but the more I do the better I get at it. Doesn't mean I'm any faster tho......it's still a PITA.

I installed and shimmed the two main bearings so everything is now ready to go back in the case. Assembly is the reverse, as they say.....

 

So.....this next one is done - sort of. Everything inside is finished and it shifts beautifully. Clancy brought me a front cover - he has a guy who machines them and puts a lip seal inside so they don't leak oil thru the mainshaft. Originally, they have a sort of reverse thread that's supposed to scroll the oil back into the box, but the front covers wear and the gap gets big enough that they leak thru and it gets on the clutch, this helps eliminate that.



However....

He brought me the wrong one - he brought one for a smooth case gearbox, and the bolt hole pattern is different.

So I have it all done save for that. He was supposed to get it on Tuesday so they could put it in a car for the races at Hallet, if they can work out the pick up schedule OK they still have plenty of time to get it in the car.

All I have to do is measure the cover so I know what size shim to put in it and bolt it on, won't take 15 minutes once I have the right cover. In the meantime I have a small bracket bolted on to hold the input shaft bearing in place.



With this one done I can now get back to work on the Mini gearbox as all the parts are here for it. I'm hoping that the various machine shops will be done with their work on the engine block, head and crank by tomorrow afternoon, but I have plenty to do in the meantime.....

 

10lbs of crap in a 5 lb box?

 

Annnndddd.........this one's done! Shifts nicely and feels solid.

Time to start the next one (of two)