Does 5th gear feel dead with 355 gears?

[V 10 MAFIA]

I'm not going to say that I was in a race but rather a test of performance against another vehicle.

My 99 R/T has a Random Tech Cats/CatBack Exhaust and K&N intake, 355 gears.

From a 50 mph roll with a Nissan 350z with single turbo bolted on a stock motor with 390 gears here were the results:

I started the roll in 3rd gear @ 50mph. At the end of third I pulled a car on the 350Z. Then at my Forth gear both cars stayed at the same mph with the 350z a car length behind. At my 5th gear the Viper dropped off with the 350Z pulling a slow walk past me and there was no catching it.

I let off around 140
Hard to believe, myself and friend in the 350z repeated this test two more times with the same result. I was shifting my car between 5800 to 5900 RPM.

Remember this was only a test. Do not try this at home.

I'm contemplating going with rockers and vec 3 to see if this will give me enough to hold my own next time.

Let me know what you guys and gals think

 

[Camfab]

A stock Viper is way past peak horsepower at 5900 rpm. Your car is heavier, has more drag at speed, and is probably making around 420+ at the wheels. His car is probably similar power with much better aerodynamics, not hard to believe.

 

[Viper Wizard]

Charlie paint your Viper RED and it will go faster!

 

[agentf1]

Wow, I had NO idea that the 350Z's could run that good. I have to say that I think the 3.55 gears only helped your 5th gear. Imagine how bad the turnout would have been if you still had the 3.08 gears.

From what I hear the 3.55's are a must and the perfect gear for a Viper.

 

[Tusc]

So a stock Viper with gears vs. a blown Z. Out of curiosity, what does the Z have for other supporting mods? I never knew they could be that much of a contender.

Sounds like you now have motivation to mod the R/T.

Time for a cam + headers... or a small shot if you prefer nitrous (easier to remove if you plan to sell the car).

 

[GotAViper]

My roomate had a twin turbo 350Z with 400 to the wheels.


I still pulled em up high, but did much more pulling in the lower gears, it was getting very even in the higher gears.

 

[valentine_viper]

Welcome to the world of forced induction. Turbo charged cars can make incredible top end power, even with small displacement engines. My 3.0 liter Supra makes my 8.3 liter Viper look stupid in a straight line run.

The 3:55 gears are probably hurting you in 5th gear. There is a reason Vipers came from the factory with low gearing. They make lots of torque at very low rpms and 3:07 gears are well suited to take advantage of that. The Z probably had at least an 8000 rpm redline, so it is able to utilize higher gears. This is the same reason that the new Z06s come with 3:43s but don't need to shift sooner than we do in a race. They redline at 7000 rpm. If you had stock gears, you probably would have pulled him in 5th.

 

[Steve 00RT/10]

[quote If you had stock gears, you probably would have pulled him in 5th.[/quote]

Only, and maybe, if above 150 MPH. Stock 3.07 gearing below here would be 1 to 1 in 4th. No matter the rear gear ratio---5th is still .74 OD. The 3:55s are not as strong in 5th as the 1 to 1 ratio in 4th with the OEM 3.07 rear end.

Steve

 

[Knight Viper]

I saw were a Viper owner had put a different 5th & 6th gear ratio in his car, I wonder how that would effect this outcome and how difficult or expensive the install is.

 

[RoadiJeff]

There is a reason Vipers came from the factory with low gearing.

Correction. A 3.07:1 factory gear ratio is a HIGHER gear than a 3.55:1 aftermarket. The higher number 3.55:1 lets it spin easier but it will run out of breath more quickly.

 

[V 10 MAFIA]

Charlie paint your Viper RED and it will go faster!

YOU BASTARD!!!!!!!!

 

[grcforce327]

Charlie paint your Viper RED and it will go faster!

Yes,it is that simple!!!

You must be registered for see images

 

[dodgefever]

V 10 Mafia
I also have a SILVER (seems just as fast as Red ) '99. Mines a GTS. I also have 3.55 gears, and mine continues to pull HARD through 5'th. I have the dyno sheet and my HP peaks at 440.6 at 5300. My TQ is pretty flat from peak of 472.8 at 3500 through 4500 where it starts to drop. HP and TQ cross at 5200. I have stock exhaust, NO mods. The engine has roller rockers, aluminum flywheel. My seat time tells me you should either still be in 4'th at 140 with this gear, or maybe just going into 5'th. In my car, 5'th still is pulling. Something seems odd about what's happening with yours.

 

[gthomas]

I started the roll in 3rd gear @ 50mph. At the end of third I pulled a car on the 350Z. Then at my Forth gear both cars stayed at the same mph with the 350z a car length behind. At my 5th gear the Viper dropped off with the 350Z

I think the problem is what gear you were in. It doesn't sound like a fair (to you) race.

 

[Sir Hiss RT10]

Yeah, i got 3.55's but i dont see why you would choose 3rd at 50 mph, mistake!!

 

[Camfab]

Guys, its got nothing to do with gears at that speed. It's called coefficient of drag and a lack of horsepower. Let's face it, low to mid 400's at the wheels are common place these days. Youv'e got torque on the little hairdryers, that's why you pull ahead initially. Pull out your slide rules and your abacus and make all the excuses you want, but your still going to lose on a top end run. Time to empty the piggy bank.

 

[gthomas]

Guys, its got nothing to do with gears at that speed. It's called coefficient of drag and a lack of horsepower. Let's face it, low to mid 400's at the wheels are common place these days. Youv'e got torque on the little hairdryers, that's why you pull ahead initially. Pull out your slide rules and your abacus and make all the excuses you want, but your still going to lose on a top end run. Time to empty the piggy bank.

I agree about 5th gear with lower gearing, BUT..... if he was in the proper gear at 50mph, he would have taken the lead and it wouldn't have mattered if the Z was catching up when the Viper went into 5th. The Viper would have already built up a great lead.

Basically, the Viper was chugging along at 50 mph in 3rd and the turbo'd Z could only keep up until the Viper got into the optimum power range for that gear. In proper gear, he would have eaten the turbo'd Z.

 

[V 10 MAFIA]

Yeah, i got 3.55's but i dont see why you would choose 3rd at 50 mph, mistake!!

Each roll started out around 55-60 mph. Third gear around this speed is perfect at a roll.
Also third gear wasn't the problem, 3rd pulled a little more than a car length on the 350Z each time we ran. Towards the end of fourth he started keeping pace with my speed and then once I hit 5th, the 350z started walking slowly past me. Once he was three car lengths ahead of me it was around 140ish. Remember the 350Z is an automatic Coupe with 3:90 gears.

I agree with what Cam Fab said about the drag factor coming into play at high speed. I also think that what Steve00 and Valentine Viper said is true, that the 4th gear with original 3:07 gears will pull harder than 5th gear with 3:55's at the same mph range since the ratio is still 1:1 in 4th as opposed to being in lower overdrive ratio in 5th.

For me to be competive with more aerodynamic cars like a 350Z turbo or a Porsche 996 TT with similar HP from 100 to 160 mph, how much additional HP will I need to overcome drag and give 5th gear more life? Would 25HP extra even be noticeable in this range? Or do I need more like 75 to 100HP ?

Thanks for all of your responses and info so far.

 

[Tom and Vipers]

...my 2 cents (oh what did they do with the "cent" key)...

The T86 is really a 4-spd with double over drive added as an afterthought.

A properly designed 6-speed "race" transmission uses diminishing spreads as you shift upwards (There are road race muncie 4 speeds that have 3rd gear rations that are under 1.20).

There is someone who makes a 5-6th replacement that reduces the insane spreads.

But frankly, the coupling design for the "countershaft extension" is onerous and fails in stock Vipers used in Germany - the Autobahn is just too much for the T56.

(rant over)
Apologies
Tom

 

[Cobraken]

Fifth & sixth gear ratios of the Viper are 0.74 & .50. The Tremec in the Terminator Cobras use 0.80 & 0.63 for fifth & sixth. They use 3.55 rear end gears. Their power comes on a little higher in the RPM band. @ 60mph in 6th the Viper turns 1250rpm. The Cobra is 1800rpm @ 60. I understand that the tranny gears are interchangeable.

 

[byron69]

Please fill in the blanks....

Stock 3:07 gears are best between "blank" gear through "blank" gear?

3:55 gears are best through "blank" through "blank" gear?

I am trying to understand the gear thing.

 

[TOOOFST]

Above 130 with 355 gears and stock power you lose to a bone stock viper.
333's are best around.