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.

_ken

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.

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!!!

[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.

Originally posted by 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.

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]

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]

Originally posted by bz1mcr
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.

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.

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…

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