Life above 110 mph

[threestar40]

When ya'll are going well above 100mph in 5th, does the shift lever feel like it is shaking fairly violently if you grab it and shift to sixth?

I feel like something is out of balance or something in my car, but it does have 4:10's in it. It just doesn't feel silky smooth like I feel it should.

Maybe I should check my main driveshaft?

Maybe it's normal...I don't know.

It doesn't visibly shake, it just feels to violent for comfort at those speeds.

While I'm at it, is top speed achieved in 5th or 6th in our cars.

Stock gears and 4:10's?


What do you think?

 

[Rob]

I would check the actual transmission mounting bolts. I have heard in the past that it's a wise idea to check these every now and then. I have never experienced that type of vibration at that speed and higher.

 

[Ken]

When I pulled my torque arm last week, the top two bolts were hardly more than wrench tight. They certainly weren't torqued to any spec. :eyerole

_ken

 

[Legalfish]

It shouldn't shake like that. Rob's advice seems pretty sound. As far as top speed - forget about 6th gear. Stock ZR1's pull their top speed in 5th. 6th is just too tall.

 

[DDSLT5]

Rick - you might be getting your top speed in sixth, but just because you have a modified engine. A stock engine with 4:10s will still likely have top speed in fifth and sixth at approx the same speed (mid 170's), but a modified engine with 4:10's will easily run out of revs in fifth and pull more in sixth. Make sure you get a pic of the speedo at 201 mph!!!:crazy

 

[95ZR1#418]

I have a '95 with 3K miles on it. When I have shifted I didn't notice anything at all so I assume it was much smoother than yours. Then again I'm pretty focused on the road and simply may not have noticed either way. I'll tke better notice next time.

 

[offshore]

I have a '95 with 3K miles on it. When I have shifted I didn't notice anything at all so I assume it was much smoother than yours. Then again I'm pretty focused on the road and simply may not have noticed either way. I'll tke better notice next time.

Hear that.

 

[Vettelt193]

I don't have a ZR1, but mine shakes too... I couldn't see where the tranny mounted up when I looked. Anyone have a good diagram? I am assuming that the ZR1 and standard vettes aren't too much different in mounting (or are they vastly different?)

 

[bz1mcr]

High RPM limit

You could be hitting the High RPM limit. At that point the PCM begins to interrupt ignition. I don't know the factory RPM limit setting for your car, but the setting is programmable. The hop-up tuners almost always increase the factory setting, as part of the PCM reprograming.

Buy the way if you have catalysts on the car, hitting the high RPM limit is a quick way to damage them. It dumps raw fuel and air on a hot catalyst. The catalyst burns it and the heat melts the catalyst. Depending on how the melt goes you endup with some combination of high exhaust restriction, rattling in the exhaust (usually pieces end up in the muffler), and high emissions. Anyway it turns out, it's a bad deal.

Don't run up against the RPM limit. Move it (by reprograming), shift to a higher gear or slow down.

 

[Jeffvette]

Re: High RPM limit

You could be hitting the High RPM limit. At that point the PCM begins to interrupt ignition. I don't know the factory RPM limit setting for your car, but the setting is programmable. The hop-up tuners almost always increase the factory setting, as part of the PCM reprograming.


Don't run up against the RPM limit. Move it (by reprograming), shift to a higher gear or slow down.

With 4:10's in the car he would be hitting the rev limiter in 4th gear at 110.

If he's in 5th he should be good till 150-160.

More than likely, he needs to torque down all the C beam bolts as mentioned earlier.

 

[Joe Shown]

7,200 RPM in 5th gear produces a speed of 118-120 MPH with a 4.10 differential ratio, not 110. ZR-1's make their max speed in 5th gear with the stock ratio of 3.45. You will actually see your speed begin to drop in 6th gear. This also is true with ZO6's. Install 4.10's and 6th gear will give you your max speed.

Joe Shown
1991 ZR-1 #1009
1990 ZR-1, Jeal 415

 

[locobob]

Hmmm, I think you mean 120mph in 4th gear. I've got 4.09's and have seen the 120's in forth. I've also seen 150mph in fifth and was not at redline.

 

[Joe Shown]

Yes, you are correct, I meant to say forth gear for 118 MPH not fifth. 6,400 RPM produces 164 MPH in a distance of one mile with 4.10's. I have not had the opportunity to run the car past this speed since I made the gear change.

Joe Shown

 

[Wegone]

Do 410s make that big of a change in top speeds ??? I shift at 7K around 118mph in 3rd with 345s…

 

[Joe Shown]

The 4.10's make a big difference. They give a ZR-1 18% more torque throughout the power curve. With 3.45's top end of third is about 118 and top of fourth about 150. Top end of fourth with 4.10's is 118 and fifth around 170. Some people don't like the lower gear because they submit that you have to make an extra shift in the 1/4 mile thus adding to the ET. I have not found this to be the case and learned that with 4.10's I could, and did, beat ZO6's in 1/4 mile runs. 4.10's will also drop your 0-60 MPH time by almost .5 second. 4'10's make sixth gear a usable gear for the street. Drive a stock geared ZR-1 at 65 MPH or less in sixth and you lug the engine and can actually watch the engine temp rise. I would never go back to the 3.45's.

Joe Shown

 

[91mongoose]

The 4.10's make a big difference. They give a ZR-1 18% more torque throughout the power curve. With 3.45's top end of third is about 118 and top of fourth about 150. Top end of fourth with 4.10's is 118 and fifth around 170. Some people don't like the lower gear because they submit that you have to make an extra shift in the 1/4 mile thus adding to the ET. I have not found this to be the case and learned that with 4.10's I could, and did, beat ZO6's in 1/4 mile runs. 4.10's will also drop your 0-60 MPH time by almost .5 second. 4'10's make sixth gear a usable gear for the street. Drive a stock geared ZR-1 at 65 MPH or less in sixth and you lug the engine and can actually watch the engine temp rise. I would never go back to the 3.45's.

Joe Shown

I disagree. First of all they do not give you 18% more torque through the entire power curve. With 4.10s you shift sooner, as soon as you shift the car with stock gears has the torque advantage (it's still in the lower gear).

As for times my car with 4.10s was slower both 0-60 and 1/4 mile as measured on public roads with a g-tech. For a true 1/4 mile race at a track I'm confident the 4.10s would be quicker, but you've got to have traction to make them quicker.

I traded my 4.10s to a guy in my club with an lt4. I would never go back now that I've got the 3.45s. I might consider a 3.73, but only if I could drive them first. The guy I traded to is wanting to dump the 4.10s for 3.45s now as well.

For street driving 4.10s = more goodyear smoke

If you really want 4.10s and you can make a trip to Abilene, TX you can get 4.10s for free if you'll give up your stock 3rd member.

 

[Joe Shown]

I have heard this argument a number of times and do not accept it. I have had both and I know that with 3.45's you will loose to ZO6's every time, and with 4.10's you win. The 18% torque increase has been proven on the dyno many times and is oft quoted by Marc Haibeck, who's ZR-1 knowledge is encylopedic.

The following is from Marc's website:

"Upgrading the rear axle gear ratio probably has the best benefit per dollar with respect to major upgrades. The 4.10 ratio is the most popular upgrade. 3.73, 4.30 and 4.56 ratios are also available. The following is from Marc's website:

The principle benefits of a 4.10 ratio are:

18% more torque to the wheels at all speeds

Sixth gear becomes a useful gear. The car can be moved around in traffic at 65 MPH without downshifting.

Has a broadening effect on the useful power band for the LT5. The throttle response is as good at 3000 rpm as it is at 4000 rpm with a 3.45 gear ratio.

Incredible throttle response in first gear and second gear"

Hopefully, we can line up some day to see which one really delivers.

Joe Shown

 

[91mongoose]

Hopefully, we can line up some day to see which one really delivers.

That would be really cool, but my car is so modified that it wouldn't be a good experiment.

What I would like to see is two sets of a four-way race. The 1st set would be a bone stock ZR-1 vs a "4.10 gear as only mod" vs a plenum / inj. housing ported ZR-1 vs a header / exhaust ZR-1 on a non-traction prepped surface. Race from a stop and from a 50 mph roll. Any of the modified cars could also have a prom to take full advantage of the mods. Race to say 170 to make it interesting, but put splits along the way to chart progress.

Second race would be the same cars at a real drag strip.

The reason I added the P&P and header / exhaust cars to the mix is those mods cost about the same $$ as gears (if you shop around and get the best value)

PS - They dyno argument for the gears ignores the real-world factor of having to shift. A more objective way of looking at it would be torque available at a given MPH, not RPM. With all due respect, Marc is in the business of modifying ZR-1s. If you buy gears from him he makes money

 

[Joe Shown]

My 91 has a plenum/injector P&P, headers, corsa, and 4.10's. What have you done to your car and how far are you from Wichita?

I can only assume that you have never met, nor had any dealings with Marc Haibeck. If you had you would never consider makig such a statement : "With all due respect, Marc is in the business of modifying ZR-1s. If you buy gears from him he makes money"


Joe Shown

 

[91mongoose]

I can only assume that you have never met, nor had any dealings with Marc Haibeck. If you had you would never consider makig such a statement : "With all due respect, Marc is in the business of modifying ZR-1s. If you buy gears from him he makes money"

It is true I have never had dealings with him, I'm sure he's a respectable guy. My statement still stands, though. My personal experience with 4.10s has all been negative as far as real-world performance is concerned. I wish there had been a nay-sayer or two on the net when I was looking to buy my car. I would've drove 4.10s and 3.45s first if there had been. I certainly would not give it a "bang for buck" endorsement. I believe the hype over 4.10s is strictly a case of "the emperor has no clothes" unless you use your car on the 1/4 mile track alot.

My '91 has stainless works headers and x-pipe, old-style triflos, a light-weight flywheel (20#), carbon fiber hood, 13# battery, baer eradispeed rotors (supposed to be lighter), custom prom, and I removed the spare tire, etc. Those are the only things of consequence for an acceleration bake-off.

I also have heim-joints, coil-overs, ron davis nascar radiator, s/d coils and wires, zr51 plates, samco hoses, hardbar harness mount and driver side pyrotect 5pt harness. I have not made any appearance mods D) If it won't make the car lap faster it doesn't go on the car.

I cooked my original motor, it will soon be built w/ ported heads, inj, housings, & plenum. I might do the 368 treatment too, I haven't decided yet. I will probably switch to an electric water pump and electric power-steering pump while I'm doing the swap.

I am about 10hrs from Wichita (I assume you mean Kansas and not Wichita Falls, TX)

I really think my above scenario is the only fair way to judge gears - racing our cars would not prove much (although it would be fun ).