frenchyd
frenchyd HalfDork
11/4/17 2:06 p.m.

I laid out my MGuar and looked on my shelves for all the bits and pieces I've saved over the decades I've been into this sport. The problem came from the transmission choice.  

A two races from new Saenz 5 speed complete with various gear sets, with the V12 conversion plate, and a Tilton triple disk aluminum flywheel.  This is a serious racing transmission, no syncros. The clutch is only used to get the car moving. Never while shifting 

Its a quick change unit so just like a quick change rear end you change gear ratios by pulling out the gears and replacing them by sliding in different sets.  I love ❤️ this gearbox but it only works for racing. The street would quickly destroy it.  

If I put it in the MGuar it becomes a race only piece. The alternative is a turbo 400 tranny .  Fine for street not so good for racing. Sure a shift kit will improve it but never to the degree the 5 speed will.  

My real love is racing.  Nothing gets my blood pumping like setting someone up for an inside pass and then taking it away. 

On the other hand my favorite race track is Elkhart Lake with it's 3 long straights  but the MGuar would be terrible there.  Short wheelbase and  bad aerodynamics are great for an autocross but not where top speeds exceed 200 mph 

On the other hand sitting in my driveway is a nice rust free XJS  that has less drag than an XKE  with a nice long stable 102 inch wheelbase.   

We know that they are stable on the high speed tracks like Daytona and Elkhart Lake.  

Ahh but time!! It would take me more than a year to build any race car and more cash than my retirement would allow.   Sure I could build one and then the other but will time and resources grant me that?  Even if I take the gamble which comes first?  

 

So so I need to pick one,  race car in the form of an XJS or street car in the form of the MGuar  

 

jdunn
jdunn New Reader
11/4/17 5:46 p.m.

In reply to frenchyd:

Why would street use destroy the non synchro race gearbox? I've run several cars with Hewland dog boxes on the street with no problem (I've got a Hewland DGB behind a Chev V8 right now). To me, it is no different than changing gears on a motorcycle, which does not have synchros, either. Maybe since I first learned to drive in my dad's non-synchro manual trans truck, this is second nature to me. And,  I always use the clutch whenever I shift.

I will admit the AL flywheel & 3 plate clutch, especially if really small diameter, makes it tricky to accelerate from a stop. But that is what i have in my car, too. I wouldn't want to be stuck in bumper to bumper traffic, but ours are not everyday go to work vehicles. At least mine is both a track and some street use type vehicle.

 

 

Is it a Saenz constant mesh straight cut sequential gearbox (GT/TT)?  It would be fine on the street except for the whole awesomeness of screaming gears upsetting the quiet. No reason you can't clutch the shifts as long as you give it a real clutch and flywheel to smooth it out. Then when you want the boogie - just pre-load, lift, bang up the rack like a boss. 

Look into an aftermarket motorcycle racing quick shifter system and rig up some micro-switches so it handles clutch blips on the downshift for you if you want a cool project and to just bang the E36 M3 out of it all the time :).

 

frenchyd
frenchyd HalfDork
11/4/17 8:56 p.m.

In reply to jdunn :I acquired it because in 6 practice laps the original owner destroyed a complete gear set.  I was able to change them out in a half an hour but he destroyed a second set.  At that point I pulled it and replaced it with the original 4 speed. ( that remains in the car to this day)!!

When I had it behind my V12 it was so sweet.  Like it knew what gear I'd put it in and magic made it happen.  Not only that but it was a real 5 speed, not a 4 speed with overdrive like most gearboxes are.  That means I could cam it to make more power in a narrow band.  

 But that was on a track at full throttle. Stuff that would get me arrested and my car hauled off no longer to be mine.  As far as the tiny triple disk, surprisingly that's pretty easy.  But the car was light and the 1st gear was pretty low 

frenchyd
frenchyd HalfDork
11/4/17 9:02 p.m.

In reply to The Artist Formerly Known as Giant Purple Snorklewacker :nope not constant mesh like a motor cycle.   I think they may have that now but that's not what I have.  What I have I can change gear sets in a half hour. Faster on the bench.  

Dog rings work different. If you clutch you crunch, crunch it bad enough and nope it won't shift.  

 

jdunn
jdunn New Reader
11/4/17 11:32 p.m.

In reply to frenchyd:

That is interesting how you came by that Saenz gearbox! You have to rev match your shifts and have some mechanical sympathy in order to operate a dog ring gearbox. Ham fisted drivers can tear one up easily, as you noted. You can tell if a driver is or isn't easy on the gearbox by examining the condition of the dog rings during service. 

I respectfully disagree with you about using the clutch to shift a dog ring gearbox. You "can" use the clutch to change gears (which I do on the street) as long as you carefully rev match your gear changes, although on the track quick shifting is possible without using the clutch by loading the shifter toward the next gear and breathing the throttle.

That disagreement aside, I think we both agree that a dog ring gearbox is a delight on the racetrack.

frenchyd
frenchyd HalfDork
11/5/17 8:39 a.m.

In reply to jdunn : I drove a tractor on the farm. Straight cut gears no synchro and had to shift on the fly to get the crops in. So yes I know how to.  In the race car I found joy in sticking the lever at just the right moment to execute a snick free shift. In pulling the gears and seeing them in perfect shape.  

I think under the right circumstances it would be possible to drive on the street.  Possible but not realistic.   

Going to car shows for example, you know how gingerly some people trailer their prized car.  Traffic jams and no consideration for others. 

Now with an automatic I can drive   like the rest of them and since it's an automatic who cares if I lose a little horsepower to a fan.  

So I build the MGuar  with an automatic and deny myself the joys in racing?  

Or do I build one last race car(XJS) and delay the MGuar something I've wanted to do for over 2 decades.  

 

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