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Discussion Starter · #1 ·
There seems to be some debate on the LS1 boards as to the difference between the Gen I/II Viper Spec T56 and the LS1 F-Body T56. Ignoring of course overall dimensions which will vary due to the application. The gearing is the same, and from what I gather you guys have a 30 spline output shaft and steel 3/4 shift fork. Can anyone shed any light on the differences or perhaps a link that breaks down the different spec sheets?

Thanks guys,
Mike
 

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I believe there are different Tremec part numbers for the Viper tranny vs. the F-body tranny, and I believe the Viper unit has a higher torque rating than the F-body part.
 

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I seem to recall someone stating that the output shaft was suppose to be beefier on the Viper, but I don't have any first hand knowledge.

I'm curious if they are going to have to beef up the tranny in some respect to handle the extra weight of the SRT/10 RAM
 

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Discussion Starter · #5 ·
KenH said:
I seem to recall someone stating that the output shaft was suppose to be beefier on the Viper, but I don't have any first hand knowledge.

I'm curious if they are going to have to beef up the tranny in some respect to handle the extra weight of the SRT/10 RAM
Well I haven't consulted tremec, but from what I understand, the F-Bods T56 has a 26 spline input and output shaft. the Viper T56 has a 26 spline input and 30 spline out put shaft. I also have heard that the viper has a steel 3/4 shift fork. But beyond that I don't know what the differences are. The Gen I/II Viper T56's are rated at 450(not sure if that's rear wheel or flywheel) and the Gen IIIs are rated at 550.

Mike
 

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My t/56 in my f-body sucks ass! It's gonna need an overhaul before the 422 goes in. And it's not gonna like the big-'ol-shot-o-nitrous either.

The T56 in my viper is rock solid and i plan on it handling some huge power in the future. They seem to hold anything. Yes you are correct, the output shafts are different for both cars. Viper t56's can handle 1000hp, but they seem to cry for mercy at about 600rwhp in an f-body; look the same but world's difference in strength.

Hey buschman! I'm Mike 01WS6 on LS1Tech.com..... PM me sometime.
 

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While we are on the subject, does anyone trust a t-56 in fifth gear at the track ? Last week I had to shift into fifth on all of my passes around 1000-1100 foot with 3.07 gears. This killed my MPH, I have a set of 3.55 gears to install, but I don't know if it will handle the torque... it rear wheeled 640 at 2900 and peaked 678. If it will take the power I would think about a set of 3.73's, it would keep me in the power all the way through fifth. I don't like the idea of pounding the tranny in overdrive. 1 to 1 in forth is one thing, but fifth is another story.
Thanks,
Joe
 

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I think I've read that the non-Viper T-56s have narrower gears on 5 & 6. They have lower torque capacity, but some additional selection of ratios. Blocker rings are different, but I don't know exactly what it is. Even Viper-spec trannies are marginal for extended high torque loadings, but drag racing won't load the gearsets very long.
 

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A little off subject, but...

Fifth gear in the 1/4 mile with 3.07 gears sounds odd. What kind of combination are you running that requires going into fifth? With that much power I would expect you to run a little less than 140 mph, which should be ok for forth gear with 3.07 gears.
 

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Discussion Starter · #11 ·
OK here's the real scoop straight from the horses mouth(ie technical rep at tremec):


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Mike,

The T56 transmission differences between the Viper, Firehawk and Cobra are:

· The Firehawk and Viper have the same gear ratios, which include a .74 5th and .50 6th gear. The 2003 Cobra has a .80 5th and a .63 6th gear. First through fourth for these vehicles are the same.

· The Firehawk and Cobra have the same output shaft size (27 tooth spline); the Viper has a 30 tooth spline.

· The most important difference is the synchronizers. The Cobra and Viper have carbon synchronizers. The Firehawk (and other GM T56 transmissions) used paper synchronizer material through model year 2001. Carbon is more aggressive, but the paper gives a smoother shift. It is extremely important to only use recommended oil with paper synchronizers. Dexron III ATF is the recommended oil. Mobil 1 ATF is the only recommended synthetic oil. Using the wrong oil with paper synchronizers will cause the paper to degrade very quickly. It is a compatibility issue with some oils.

· The Viper has a single piece countershaft where the GM and Ford transmissions have a two piece countershaft construction.

· There are bolt pattern differences, but essentially the rest of the transmissions are the same.

I hope this answers your question.



John Loeffler

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So I guess we were all close, but now we know for sure. Tremec responds fast as hell. I didn't ask about the difference between a Gen I/II Viper T56 and the Gen III but I'll try and find out.

Mike
 

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I know that the sixth gear in the tranny is a weak area.
 

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John Myrick said:
Fifth gear in the 1/4 mile with 3.07 gears sounds odd.
I think he's talking about road racing and having to shift into 5th on 1000 ft straights.

After re-reading it maybe not. Hell, I dunno.
 

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buschman said:
**************************************************************
· The Viper has a single piece countershaft where the GM and Ford transmissions have a two piece countershaft construction.

************************************************************************

So I guess we were all close, but now we know for sure. Tremec responds fast as hell. I didn't ask about the difference between a Gen I/II Viper T56 and the Gen III but I'll try and find out.

Mike
I seem to recall that the Gen I / II Viper trannies had "something" that was two piece vs the Gen III Viper tranny having that "something" as one piece - I would suspect it is the countershaft given the above info, and that he was giving you specs on the Gen III Viper tranny - no guarantees, just something I recall when going through my most recent Viper new tranny installation, which mentioned that the Gen III Viper trannies were stronger due to the one piece vs. two piece "something".
 

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Hey guys,
I don't want to steal this guys thread, but I am serious. At the drag strip, shifting off of a 5600 shift light I need to shift into fifth. I tried running it out in fourth and hit the limiter at 6200 about 100 feet from the finish line. On the pass on the limiter I ran 130.9 mph, when I shift it dropped to 127.5. I am leaving at 2000 rpm with a mid 1.60 60 foot time on a 345/30/18 drag radial, 6.90's @ 100 mph in the eighth and 10.70's in the quarter. I thought is was very bizarre also. I have a different cam and a aluminum flywheel, but I don't think it should make that kind of difference. Everyone else with similar times are going through in forth at around 4800-5200 rpm...what gives. From what you guys posted , you think I am nuts, nuts maybe...confused definitely. Any ideas would be great.
Thanks,
Joe
 

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>>>I would suspect it is the countershaft given the above info, and that he was giving you specs on the Gen III Viper tranny - no guarantees<<<

John, I think this is correct.

We had some tranny failures in Germany/Switzerland due to the 2 piece countershaft. I guess that since we drive the Viper on our Autobahns in 5th and 6th gear we see more tranny problems. The connection between the two parts is the weak point.
 

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Without true knowledge of the tire diameter I can only estimate the tire dimensions. Using the sidewall numbers of 345/30/18 calculates to ~26.1" diameter and 82.2" circumference. Since fourth gear is a 1:1 ratio, multiply the circumference by the engine speed. That will give you inches/min. Divide by 12 to get feet per minute and divide again by 5280 and you have miles per minute. Multiply by 60 and you have miles per hour. For your example of 6200 rpm, I get 482.6. Divide that by the speed that you saw at the track, 130.9 mph, and you will have your rear gear. I get 3.69. That's pretty close to a 3.73, so my guess is that you already have 3.73's in the car. Looks like a change to a higher rear gear (lower numerical number) will eliminate the need for fifth gear.
 

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Discussion Starter · #18 ·
BLACK GTS said:
Hey guys,
I don't want to steal this guys thread, but I am serious. At the drag strip, shifting off of a 5600 shift light I need to shift into fifth. I tried running it out in fourth and hit the limiter at 6200 about 100 feet from the finish line. On the pass on the limiter I ran 130.9 mph, when I shift it dropped to 127.5. I am leaving at 2000 rpm with a mid 1.60 60 foot time on a 345/30/18 drag radial, 6.90's @ 100 mph in the eighth and 10.70's in the quarter. I thought is was very bizarre also. I have a different cam and a aluminum flywheel, but I don't think it should make that kind of difference. Everyone else with similar times are going through in forth at around 4800-5200 rpm...what gives. From what you guys posted , you think I am nuts, nuts maybe...confused definitely. Any ideas would be great.
Thanks,
Joe
There's three reasonable ways to correct your problem.

1) Get a taler tire. By having a larger diameter tire you are increasing the top speed of each gear. To do this you must have a way of reprogramming your computer to account for the larger tire size for such things as speedometer. Unless you have a set of track only tires then if you don't mind your speedo being off and the possibiilty of throwing a code, you wouldn't need reprogramming.

2) Raise your rev limit. Again, a higher top speed in each gear. This should not be done on a car with no valvetrain work. You need to at least upgrade your springs to raise your rev limiter. I'm sure there are guys that can tel you what mods to do to raise your rev limiter to the level you want it at.

3) Lower your rear gear. This will change the way al your gears feel. Over all acceleration will be reduced, but depending on your torque/horsepower/and over all configuration your times could actually get better. Again you'll need computer reprogramming for this mod.

Hope this helps,
Mike
 

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ViperGTS said:
>>>I would suspect it is the countershaft given the above info, and that he was giving you specs on the Gen III Viper tranny - no guarantees<<<

John, I think this is correct.

We had some tranny failures in Germany/Switzerland due to the 2 piece countershaft. I guess that since we drive the Viper on our Autobahns in 5th and 6th gear we see more tranny problems. The connection between the two parts is the weak point.
Tom Sessions, the Viper tech, was mentioning something of this sort to me when I had to get my last tranny put in, in relation to the fact that it was my 6th gear that went out on it - probably something to do with peaking it out at 300 MPH! :burn: /images/graemlins/gr_driving3.gif /images/graemlins/laughing.gif
 

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John,
That sounds great about the 3.73 gears, except I just put a drain plug in the diff housing and checked the gear ratio... it is 3.07 gears. The tires are 26 inches tall which leaves me the same dilema.
Buschman,
I put new comp springs in with the new cam, I set height and set seat pressure at that time. The heads have been milled .040, and it has new push rods with a set of T&D's. There is no need to push the motor any harder because it quits making power at 5600-5700 rpm.
Thanks,
Joe
 
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