BugEye Dave's Transmission Rebuild

Started by MiniDave, March 17, 2021, 10:35:45 AM

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MiniDave

As the name implies, this transmission is going in Dave's Bugeye Racecar - I got the name and the referral from Clancy!

The tag on the gearbox said "broken third gear" and this is a backup transmission for the car. When I got the cover off - boy howdy is third gear broken - all the teeth are gone!

I only started tearing it down, the red rag is only there to sop up oil.

I got the tailshaft and shifter off OK, next step is to drop the laygear into the box to make room to move the front gear forward enough to remove the snapring that locates it in the case. It then gets pushed back thru and into the inside of the case to remove it, but first you have to remove the main set, then the lay gear, then it can come out. Lots of little bits and bobs to remove before you do that, like all the shift rods, detents, springs and forks.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MPlayle

Looks like plenty more damage in there than just third gear.  The synchro to the left looks damaged as well as the gear above/behind third.


MiniDave

#2
I think that's the laygear, and yes since it and third run together, they both are trashed. I'm putting all new straight cut gears in it, including the new laygear obviously,  new bearings and new synchros so all the rotating parts should be good to go.

Next up - the real "fun" part - removing the 2nd and 3rd gears from the mainshaft. Both are held in place with some tiny little spring loaded pins, that engage a notched plate - the fun is being able to push the pins in so you can rotate the plate to match the splines and slide it and the gear off - without sending the little pins into orbit never to be seen again!

All the gears and shafts are out of the case which was really clean inside - I'm guessing this one's been rebuilt before. In the first pic you can see the carnage....,too much HP for these gears, these engines only made about 60 hp, and they're running more than double that now.

Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

BruceK

Is this for a street car?  If so, do people still fit Datsun 210 5-speed transmissions to Spridgets instead?  Or are they too scarce these days?
1988 Austin Mini
2002 MINI Cooper S
1992 Toyota LiteAce (JDM)
1997 Jeep Wrangler Sahara

MPlayle

With going to straight cut gears and the HP mention, I am guessing it is for a race car and they may not allow the 5-speed swap.


MiniDave

#5
Yes, sorry.....it's a racecar. I amended the first post to reflect that....

I can rebuild one of these with the straightcut gears for less than $2K where the 5 speed conversions are closer to $5K, and of course not allowed in this race series.

I would want a 5 speed gearbox for a street car, if just for the lower revs on the highway.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

pbraun

that's a lot of crap to be floating....... around in a gearbox. Good luck with the rebuild!
Peter
65 Moke
60 Bugeye modified
66 Jaguar XJ13 ( I can wish )

MiniDave

Yes, I'm surprised actually that there isn't more damage with all those teeth loose in the case like that.

Today I'll strip the gears off the mainshaft then get every thing cleaned up and ready to re-assemble.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

jedduh01

Glad you know what you're doing!    For me. Mini transmissions are Amazingly simple - RWD sprite Ribcase = not to me!

I once disassembled a Ribcase.. then all the balls + Detents + springs + of course went everywhere + didn't know where they went back... That 'core' Remained forever a core. I was looking for why a reverse + first was SO LOUD from this car... Gears LOOKED fine.
 
That core ended up going to CT for a rebuild by Quantum =  inside someone PREVIOUSLY had been in there and mismatched Laygear to the gearset = creating the NOISY first + Reverse.   Wouldn't have fixed it anyways.

I dont want to re open a ribcase again!


MiniDave

I know exactly what you mean, first one I did took me two weeks to figure out where all the detents went.....I must have had the forks and shift rods out of it ten times. I wound up contacting a guy in England who walked me thru it. I guess the ribcase trans is getting scarce in England, we have a lot of them because most of the Sprites and Midgets built came here

I bought extra pins for the gear retaining plates when Vicky Brits was still in bidness, and of course extra detent balls and springs for inside the shift sleeves, It's not unusual for me to loose a couple of those when I'm putting the shift sleeves back together.

If you ever come across a case - rib or plain - where it's not rebuildable, I'd like to get one so I can cut off the bell and use it in my engine stand. As it is right now the flywheel is exposed when it runs.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#10
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.....
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

Clancy got me another gearbox, so I stripped it down and now have the right mainshaft to build Bugeye Dave's gearbox. More as it happens.....
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#12
Ok, so here's the difference between a smoothcase or Morris Minor gearbox and the later ribcase - BugeyeDave bought this transmission from Vicky Brits already rebuilt over 25 years ago. At that time it was just a street driven car and didn't become a full on racecar till much later in it's life - that's when it blew third gear to bits! So either they put smoothcase stuff in this ribcase case - which was not uncommon way back when as the case is a lot stronger too -  or like I said, it's a MM transmission.

So Clancy had dropped of another transmission earlier for me to rebuild  but frankly I though the case was suspect - it had clearly broken and been rewelded and while it looks fine, I don't know that I would trust it to be straight and true. We decided to rob the mainshaft from it to use in BugeyeDaves trans, so I stripped down the new mainshaft so I could change the gears from helical to straight cut.

In the first pic you can see it uses the same pin and plate arrangement as the earlier gearboxes, but when you get that plate off you can see a row of needle bearings - that's the big difference. That and there is a boss machined in the later mainshaft for the 2nd and 3rd gears to ride against that the earlier trans doesn't have, instead it relies on a brass plate between the gears.

Once 3rd gear is off, I flip the shaft over and take out the harder plate - it has two pins, and some small half moon plates that ride under the pins and fit inside the plate on the top. It's a lot of bits to juggle around when it goes back together - but I've developed a secret way to get them off and on now. I use some assembly lube to hold the needle bearings in place on the shaft while I carefully slide the gear down over them.

Then there's a pic of the two mainshafts to show the difference, and the assembly all done. Last pic shows the input shaft and laygear installed, however, to put the mainshaft in the case you have to pull the layshaft out of the laygear and let it drop down into the case so the mainshaft gears will clear those on the laygear. Once the mainshaft is in place then you raise the laygear back up and slide the layshaft into it, making sure not to drop the end washers out of place, cause they can bee a bugger to get back in with all the gears in place.

After all that the next phase is to get all the detents and springs in place - I counted 5 pins and 2 balls that have to be put in the exact right place for them all to work correctly. Once those are all done, I'll put the tailhousing on and shim the rear bearing, then install the shift linkage and lastly I have to shim the front cover bearing too. Before I put the sidecover on I have some plates I made to hold the detents in the case while I shift it thru the gears to make sure they all work. If they do the side cover goes on and it's done and ready to race. Still a ways to go on this one.

Edit: somehow the pics got all out of sequence to the story - sorry.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

Much better, this one won't break unless he does something wrong.

Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring


MiniDave

Yeah, I had to stop for a while, maybe for the day.....this looks correct at least, all the gears line up neatly and the bearings are in place. Next up, all the detents and shift rods and forks.  62.gif
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

PoolGuy

Sorry only just seen this, this might help http://www.dorsetmmoc.co.uk/wordpress/tech_articles/Gearbox%20rebuild.pdf as you say it looks like you had a Minor box. In the pdf, look out for the tip about restricting the 1st gear selector.

MiniDave

Thanks for that Poolguy, that's a nice PDF. Interesting trick about using the garden twine to hold the pin in while you slip the lock plate down over it.

This is my 5th Sprite gearbox rebuild (but the first that turned out to have this style gearset in it), but there was a pretty good gap back to the last one so I needed to remember all the tricks again. The last one I built is successfully running around the midwest's racetracks, and the owner is super pleased. The one before that is in a Lotus 7 owned by the guy I'm building the race engine for, I'll probably build him another for this racecar once he recovers financially from the engine rebuild. Before that was a standard ribcase being used in a Bugeye, this one and then the first one I did is back before it was ever used for me to put a set of straight cut gears in it, so I'll get to see how I did with it.

Chances are this latest box won't be used, it's a backup gearbox just in case as he runs a dogbox in his racecar, but this would at least allow him to finish a weekend if he lunches it somehow. I'd like to go thru one of those someday....

But it's great to have such a good reference as this PDF. There are only a few differences, the 2nd gear retainer is done differently and 2nd and 3rd use needle bearings instead of bronze bushings. Other than that and the size of the gears themselves, it's all pretty much the same.

Thanks again!
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad


pbraun

nice job! I had trouble with mine, and eventually gave up and got a Moss rebuild for a grand on sale.
Peter
65 Moke
60 Bugeye modified
66 Jaguar XJ13 ( I can wish )

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