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150-170 MPH Top Speed + Fuel Efficiency 5th Gear


Oscar_the_Grouch
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Oscar- have you looked into using the supra 5 speed? id hate to beat a dead horse, but i heard that you could use it with an adapter plate on the bell housing. maybe those gears will be better top end-wise. cheaper too.

 

just throwin some ideas around.

 

-chris

 

Hello Chris

Well to be honest I have NEVER seen the inside of a transmission, I can tell you wether its a manual or a 5 speed but assides from that I donr have a clue. So I am letting PRO's do this mod for me. Hey I am originally from Florida and you know what reputation Florida has with numbers !  ;D So as soon things get to the point that you have to totally design a new part thats were I DRAW the line. As for the Supra tranny, well I have no clkue as well but I will point it out to Stedebani to see if they kow anything about this. But somehow I dought it will "JUST DROP IN"

 

But all of you guys that have replied will be keeped updated and new guys have been added to the list.

Thansk

Oscar

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  • 2 weeks later...
Just a thought.....you might check with some of the Ford broncoII 4x4 guys.  I believe they have a mitsu trans in a 5 speed with the same ratios. Maybe someone has done some of the 'leg work' for you already.

 

 

Well thanks for the heads up and I'll try to look into it.

BUT I dont think a Bronco II will be doing 150MPH any time soon !

Also I believe the ONLY other car that shares the same or almost the same Trany iunternals is the Montero and the Mighty Max.

 

I'll look into it though !

Thanks

oscar

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I'm interested like everyone else.

 

I have both an auto and a 5spd

 

the auto runs right at 2500rpms @ 70mph  2000 @ 55mph

with the .686 (or so) ratio

 

So something close to that perhaps something like the stang guys a .65 or something but .5 damn our cars would be in so much of a lug it wouldn't hardly go hell you'd have to have it floored all the time in 5th then.

 

Put it this way when car & driver had a modded vette that ran like 212 in 5th (.70 ratio) they shifted to 6th gear (.50 ratio) and the damn thing slowed down to like 176.  and were talking about a very good areo dynamic car with lots of great power to go 212MPH!!!!

 

.5  is out of the question for me.

 

However I've heard that straight cut gears are stronger and someone else posted they the heli cut are able to handle more torque?? so please inform me more about this because I would like to know if we could make our trannys better by replacing the other 1-4 gears with straight cut??

 

Zero

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Jay

 

That may be a good idea BUT since it's Stedebani who's doing the gear its just a matter of time before they get down to it.

 

They have come though for us with the Poly Bushings, Short Shifters, Camber Plates and Strut bars and besides they have already done this for the Eclipse so my money is on them.

 

So patience is a virtue.

I'll add you to the list Jay

thanks for the interest

Oscar

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I'm in on this but at the same time would be curious to see the price on both cut's. When I'm passing some ricer on the freeway the only thing I want him to hear is the BOV as I shift into 5th to hit that 150 8) All the same, please include me on that there list if ya could.
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Well as far as Stronger THEY ARE as far as I've heard as well.

They can take A LOT more torque and abuse than Helical Cut gears. Thats why most ALL racing tranis use straight cut gears, they are a bit tricky to shift into them in a lower gear like 1st and 2nd as the synchros dont do much for straight cuts.

 

All this if "Heard of" info and NONE from personal experience.

But the price is expected to be DOUBLE for a Helical Cut vs the Straight Cut. But nothing has been determined yet.

 

This may be a "Tax Refund" GP as it may take that long or longer to get developed and tested.

 

Oscar

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Guest silverngray

Straight cut gears are used in semis and racing trans. They are much stronger. But you must match engine speed with transmission speed to get them to engage. That is why it is harder to downshift. You have to rev the engine to get them spinnin at the same speed. Wouldnt be much of a problem though for only top gear.

Rico

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  • 2 weeks later...

OK, lets get a few things straight...

 

First:

Straight cut gears shouldn't shift any harder than helicals.  The gears in your tranny are ALWAYS in mesh, when you shift you aren't moving the gears sideways to engage/disengage with each other, you're moving dogs or couplers which connect or disconnect the gear from its shaft.  Semi and race transmissions require speed matching because they don't use synchros like a street car tranny.

 

And furthermore:

All the ENGINEERING sources I've read state that helical gears have Higher load carrying capacity than comparable sized spur[straight-cut] gears.  Speedvision may say differently, I'll trust the engineers that write my books.  That being said, you should NEVER have a tooth-strength-related failure in 5th gear irreguardless of the gear cut.

 

Which begs the question:

Why do race trannies use straight-cut gears?  Efficiency.  Straight-cut gears are slightly more efficient than helical ones, and saving a few percent horsepower is worth making the gears a few ounces heavier for the same strength.

 

About gear noise:

Your reverse gears are helical cut gears.  The whining in reverse is produced because they produce a thrust load on the countershaft in the direction opposite that of  the forward gears.  The tranny is designed to take big thrust loads in the forward direction, but not in reverse because it's not used at high speeds or long periods of time.  That whine is a bearing noise, not a gear noise.  In fact, a straight-cut gear noise might now be too bad.  Those who've ridden motorcycles, does the tranny noise bother you?  Never even noticed it.  Those are straight-cut gears.

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I always thought straight cut gears were stronger too. I did a little looking and from the little information I read, helical seem to be stronger, but that doesnt do you much good they put a lot of side load on the bearings and so on. So that would be why mostracers use straight cut, but I think someone has already mentioned this. It's not to say straight cut are weak either though... There is a lot of garbage to sort through to get any solid information on gears heheh.

 

I'd rather see the 6 speed gearbox, but this is cool, a cheaper way tog et more top end, but I hope most of you don't plan on going 180 on the highway.  :o

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