shep trans strength

[dsmtalontsi95]

I'm looking into a shep trans stg 3 with the chromoly shift forks, rem isf, and the double synchro 3-4. The car it's going into is a 2nd gen with a 2.3 stroker with a frank 3 (I know old technology) pushing around 30psi. I plan to upgrade to a gt35r like turbo, I haven't decided yet. Do you think this will be enough for what I want to do? I'm coucious about the center diff. This is my weekend car and so I want the 4 spider diff, but I'm worried about the strength of it. I don't want to be replacing this all the time. Is this going to be enough for the track?
click

 

[marvinmadman]

I would have to say that "shromoly" is some very strong stuff. It is made of the usual chromoly but infuzed with stainless. /ubbthreads/images/graemlins/grin.gif

 

[dsmtalontsi95]

fixed.....lol

 

[Bimmubishi]

It will hold about 450 ft lbs max. That's the consensus.

 

[Boostin21]

I went EVO III gears, shot peened, double syncro everything. Tons of goodies. I plan on making 600ish...

 

[Bimmubishi]

You'll be on the edge of reliability but it's the best non dogbox option you could do.

 

[3rdstrikedsm]

It will break it is just a matter of when, Strokers are way harder on the trans due to the amnt of torque the make.

 

[atc250r]

At the end of the day it still has OEM gears in it. Maybe if they were cryo treated it'd help some but I don't know how much. Lots of guys run single digits on OEM gears, its all in how you launch it and how you treat it.

John

 

[Barnes]

IMHO, and I really am not a serious source, elecropolishing, or shot peening would make the most sense in increasing reliability. From a mechanical failure perspective, it would help the most.

 

[Bimmubishi]

I could have my wires crossed but I think John from TRE told me that the Evo gears are factory shot peened and that's where they get the 'little' extra strength from.

4th gear is undercut to fit the bearing which is why 4th (this also according to Magnus) is the weakest link.

AS you can see in the blurry photo below, the actual support area for the gear is half the thickness of the gear itself.

 

[atc250r]

It sometimes amazes me the amount of stress that can be handled by a small amount of steel like that. On older Dodge trucks like mine, the 5th gear "nut" has a nasty habit of coming loose and allowing the gear to slide off without warning and then you lose 5th. Luckily there is no damage done and people have gone 10,000 miles without fixing it. When mine came off and I went to fix it I couldn't believe that the splines that 5th fit into are less than 1/2" and about 1/2 the thickness of the gear yet it will live at 800lbs/ft of torque without a problem.

John

 

I would say a lot depends on the clutch.

 

I'm currently runnin a stg.2 build by Jacks Transmission down in CO Springs with the 4 Spider and for daily usage and track usage I can personally tell you that its amazing.. I've snapped two axles on my build so far an neither have faised the trans.. I have the double Bronze syncro 1-2, beefer input shaft, 4 Spider Center diff, bead blasted case, etc. etc. and love it.. I've got around 15,000 miles on mine and have no problems whatsoever.. In case you didn't know Jacks Transmission and Shepard work together sometimes and their trans. are very comparable.. I would go to the extent of calling them competetors at this point.. I also have a friend running the reman stg. 3 Shep Trans an at around 22k miles he started having trouble due to the fact that shep used the Brass Synchro's instead of Bronze for his Double 1-2

 

[Bimmubishi]

In the case of high power, assuming that the transmission is built correctly, no amount of STG 1, 2 3 whatever will make the gears stronger. The Evo 3 shafts are the strongest available outside of a dogbox option. The clutch could have played a factor in my transmission breaking but there's not a whole lot of impact force from 3-4th (unlike launch to 1st or even 1-2.)

 

^ Bim has it right. The weakness of 4th is simply due to the fact that it has the least cross sectional area off all the gears.

With that being said the easiest solutions to this are : 1) make the car lighter
2) make less torque

 

[slugsgomoo]

seems like most of the people breaking 4th are doing it when the gearbox is pretty hot, since even with retarded power and 150+mph traps guys are keeping 4th in the car /ubbthreads/images/graemlins/dunno.gif

I know that a cooler is a potential help to the situation at least, but there really isn't a way around 4th gear unless you go to a dogbox. /ubbthreads/images/graemlins/mad.gif

 

[Bimmubishi]

It's undercut to fit the bearing. That's the problem. All the other gears are as wide cross-sectionally as the gear face except 4th.