No Problem Eric,

About the speed reluctor,

The Fbody reluctor and the Viper reluctor have the same OD so the VSS sensor should read the Viper sensor with no problems. The only problem that I had with the Viper sensor was that there was a very large difference in the number of teeth. I was concerned that I wouldn't be able to rescale the VSS enough in LT1Edit to account for the difference. So I reused the Fbody reluctor by boring it out for a tight fit over the mainshaft splines then tapping it on during final assembly. It works fine. Will suck the next time I have to disassemble though. Let me know if the Viper ring w/ rescaled VSS works because I think that's the preferred way.

Steve

 

Thanks for the pics.

IMO, from what I can see, the failure is not due to any void or defect in the material. It looks like a classic torsional failure. My guess is that it failed with a bang either at launch or during a hard (speed?) shift.

Does the broken off piece fit into the depressed piece shown fairly closely? From what I can see, the shiny area in the very center is where the pieces rubbed after the failure until you shut it down. There should be a mating shiny spot in the other piece.

The snap ring groove with sharp internal corners is the weakest point and is a "stress riser" and where it will fail when repeatedly overloaded. If the overload is enough, a part will fail on the first cycle. Otherwise it's a matter of time (or cycles). Design criteria are for no failures after millions of cycles.

My $.02

 

it failed on a launch, the shiny part is most likely from us trying to figure out what the heck was going on and trying to put it into gear and it not going anywhere

justin

 

Just got my trans back from Donato Engineering with the Viper mainshaft upgrade. With the new Spicer yoke it was about $675. He has the standard 3150/3110 combo joints but if you have a carbon shaft like me you will need to find a different joint. I am still looking but I know its out there. Much bigger shaft though and if I break it, oh well. E-mail Donatoeng@aol.com and let him know Doug from MD sent you about the viper conversion. He should have his website up soon with pics of my trannny being modified. Good luck all!

 

Is there any new info on this subject as i just broke my out put shaft in 3 runs with the street twin in the car not to mention a broken drive shaft to go with it : (

Steve

 

Thanks to Steve's help, my car is now back on the road with an upgraded trans.

I ordered up a used Viper T56 mainshaft, and the Viper-specific bushing, seal, speedo reluctor (also a used part), and reluctor snaprings. This was around $225 from D&D. I cut 3/4" off the mainshaft using a chopsaw (this is not an easy task), and assembled my transmission around it. Fortunately, the bearing clearances were spot-on and I didn't have to mess around with the shims.

I opened up the tailshaft housing using a Bridgeport mill with an Easytrac setup, but a boring bar would have worked just as well if you don't have access to a CNC-equipped mill. I don't have the dimensions here at work, but I seem to remember shooting for a 0.005" press-fit for the bushing and the seal. This is pretty tight, and I'd consider opening that up by a couple thou the next time around (no problems with driveshaft yoke fit, though). If you pay a machine shop to do the work, I think that you'd pay for about 2-3 hours of labor.

I used the 10-tooth Viper speedo reluctor, and it works just fine with PCM programming. In LT1_edit, it's a simple matter of multipling your current "speedo" and "trans" gear values by 0.588 (10 divided by 17). No problems there.

I ordered up a new driveshaft from Denny's. The new output shaft using a regular 30-spline Chrysler yoke, which is supposedly a bit tougher to obtain than your standard 27- and 32-spline yokes. Denny's set me up with the driveshaft and both yokes (I swapped the pinion yoke over to a 1350-sized part) for $410 or so.

So, it's back on the road and all is well, but I don't know that I'll be putting it to the test at the strip any time soon, as I missed too much autocrossing last year due to broken drivetrain parts.

 

Glad to hear your back in business Eric. My press fit was about .003" and that seemed about right. This upgrade so far has been all benefit and no down side. Not too many mods that we can make that claim on!

Now go beat on that T56!

Steve

 

did you ever get one?

brook

 

Glad to see this thread ressurected.

Since then, D&D has pretty much refused to sell individual parts for this swap and sells a complete conversion kit for $750. This includes the extension housing ($250 core charge) already machined and a F-body-specific reluctor gear to fit the viper shaft.

Last time I emailed John Donato he was working on a similar exhange program for pre-machined kits for around the same price.

In addition to the shaft upgrade, the known 3-4 steel shift fork (from the Viper), and the carbon-fiber rings (ala Viper and Corvette), there's also a new option of purchasing billet-steel syncro struts/ slider keys. These come in sets of 3 for each synro assembly.

The 1-2 assembly uses one size avilable from D&D, while the 3-4 and 5-6 assemblies use a different size. Each 3-key set is about $75 to $99 depending who you buy from. While you could buy all 3 sets (9 keys total) for about $300... the most common breakage occurs in the 3-4 syncro and would be a good upgrade on it's own. These keys seem to break when the shifter is slammed in to 4th gear and it over extends the keys. This apparently happens after the case has been used extensively and the built-in aluminum stop gets "clearanced". Using a aftermarket shifter with a properly set shift stop will help I'm told. I use a Pro 5 and set the stop precisely for the 3rd and 4th gears.

Lastly, you may want to inspect/replace the sliders or the gear lock-out selector plate. There was an article in Pontiac High Performance where Rockland Standard Gear talked about stress fractures in the plate after hard use, some speculate the CAGS system causes this problem. Disabling cages is a nice fix IMO.

The Pontiac High Perf article also mentioned that Rockland uses a larger silicon-broze bushing one part in the tranny, but it's been a while and I don't recall the specifics.

Beyond known fixes, there's also the possibility of having certain bearing surfaces coated with Casidium to reduce friction, but I honestly havn't heard of anyone going that far other than one Viper owner who looked like a poster child for internal coatings... and that was only in a signature block.

My tranny's making some unhappy noises at 70mph now... I'm sure I messed up the output shaft on one of the past rear end explosions (or maybe it's the 212,000 miles on her ).

I'll send John an email and see what he has available.


BTW, the 2005 Viper had a few updates to the gear assemblies, apparently there was some attention paid to a new mounting method for 5th and 6th gears. Any more strength beyond this stuff and you'll be looking at a G-Force tranny with a $3000+ kit you install yourself. (Although they do have a $2000 upgrade for Vipers/F-bodies that want the corvette's 3-ring syncros on 3-4-5-6).

 

Quick correction... I found the mail John sent me a long time back regarding the 5th and 6th gear cluster (we were discussing the Car & Driver, and the Road & Track articles in the new 2003 Viper):

John also offers a tranny cooler set up for those that use the T56 at sustained high speeds:

I imagine you could fit a differential cooler/pump set up for this use, but drilling/tapping a strong enough housing section, and finding the right place to direct the cooled fluid would be the real trick.

At the time (9/9/02) John was offering the Viper conversion for $495 + S&H + core... wish I'd jumped it then.

 

figure i may mention in here that my t56 with the custom output shaft mentioned in this thred and many other upgrades is up for sale.

please email me if your interested

brook

 

A few more additions to the T56 build-up:

G-Foprce Transmissions has some pricey aftermarket T56's that reduce the helical angle and tooth count of the gears giving them some additional beef. The gears are also made wider than stock. A high nickle alloy and a 300M output shaft upgrade are possible if you have a C5 or go to a C5 output shaft with the $2000 conversion kit they have. The conversion kit replaces all the gears and syncros and allows you to run the C5's tripple-cone syncro on all gears, not just in the 1-2 as stock tranny's allow.

The expensive Vespel pads of the past seem to have been replaced now with brass pads available from several outlets for about $10 a pad.

Gear finishing (REM isothermic and Micronite) seems to be the next trend in performcen improvements. While high-speed motorsports have been doign this for several years, it's now possible to have your rebuild include it for anywhere from $250 to $400 a tranny (only gears and sliders need it). There are a few out there but any good tranny shop can help you find one. Benfits include reduced wear, longer life, and lower temps (most claim 20 to 30*F drop, though Rockland Standard Gear said 40 to 60... depends on the applicatiuon I imagine). With gear fluid being cooked aroudn 275*F this may be a good option for those in Open Road Racing (sustained high speeds). reduced friction may get you 3 to 5 hp as well.

There is also some updated Viper gears that have larger synro teeth to prevent sheering issues. I'm told by the rebuilders I've talked to that VERY few T56 ever have this problem, but with the right conditions (I.e. slapping 2nd) and enough torque they have seen a few 2nd gear issues. I'm talking to Rockland Standard Gear in obtaining a updated 2nd gear while the tranny's open. Should be good insurance... just in case.

 

cryo made my output shaft survive!

very cool to see someone getting a better shaft made!

 

The problem with the 27 spline shaft (even a 300M or cryo treated one) is that it's just as hard to get the splines in the slip yoke to survive. I was ginking the female splines all the time before I stepped up to the larger Viper output shaft. The higher spline count on the Viper shaft solves 2 problems with 1 modification.

Steve

 

this is an old thread, what became of the 300M shafts? any good? any testing with other materials?

i need to pull my trans here rather quick and reseal it, it needs some new syncro's and maybe a fork upgrade, i don't need a shaft yet but who knows, it may not be far off.