Car slower since 3.46?

Hello,

So most of you know I put a 3.46 diff in my ZHP some time ago. I had someone comment on my youtube video I did of the car when it had the 3.07 and when I watched it, it seemed like it is faster with the 3.07. I don't know if it is because 1st gear is more useable, or because you can hit 60 with only one gear change, I dunno? I am honestly thinking of going back to 3.07. Thoughts?

Well you obviously feel the torque more with your current setup. But the 3.07 would be longer gearing of course. I have a 3.07 in my car. But if I had a 6spd I'd probably keep the 3.46.

Yea, I don't mind the RPM's being higher. And I know 6th gear is stronger with the 3.46 which is nice, but I am just thinking it is actually faster.

Originally Posted by smolck

Yea, I don't mind the RPM's being higher. And I know 6th gear is stronger with the 3.46 which is nice, but I am just thinking it is actually faster.

It might look faster on video. But we both know realistically it isn't in real time.

It`s almost physically impossible for the car to be slower, because with the 3.46, you`re getting an additional 10% torque multiplication earlier in the power curve. The downside is, you`re losing maybe 5 to 10 mph "maximum speed in each gear", which necessitates more frequent shifting. IMHO, the most important thing for you to do is to evaluate if your current gearing setup is *more* suitable to your typical driving scenario compared to how it was with the 3.07.

Car might be slower 0-60 because of the extra shift, but the 3.46 is better for your clutch, and is the better choice for track and general driving.

Originally Posted by Fast Bob

IMHO, the most important thing for you to do is to evaluate if your current gearing setup is *more* suitable to your typical driving scenario compared to how it was with the 3.07.

Which leads me back to 3.07. With the miles I rack up, it is probably a better option. 3.46 was fun, but looking to swap back in a 3.07.

And that's why I'm glad that I never made any changes to my ZHP.
I think the BMW engineers have a pretty good idea of what they're doing.

Originally Posted by jetblackbimmer

And that's why I'm glad that I never made any changes to my ZHP.
I think the BMW engineers have a pretty good idea of what they're doing.

Yeah they did from 2006 and older. I wouldn't say the same for years past that... I'm pretty sure they have absolutely no idea what there doing anymore

Originally Posted by MalibuMafiaV

Yeah they did from 2006 and older. I wouldn't say the same for years past that... I'm pretty sure they have absolutely no idea what there doing anymore

Lol

Ignore 0-60 times and internet drag racers, and ask "what feels better". On the street, the feel of speed is far more important that actually going fast.

Originally Posted by cwsqbm

Ignore 0-60 times and internet drag racers, and ask "what feels better". On the street, the feel of speed is far more important that actually going fast.

exactly.

Yes, but my posterior dyno says 3.07 feels faster. I also drove another stock ZHP and mine felt slower.

What does 3.07 feel like?

Originally Posted by smolck

Yes, but my posterior dyno says 3.07 feels faster. I also drove another stock ZHP and mine felt slower.

One way to be certain is to clock your times with something like a G-Tech Pro....do you have access to one of them ?

The 3.46 will be faster off of the line. The 3.07 has a better top end.
I raced a person with a Chevelle 396 SS one time (not recently). I had a 3.08 rear axle. He had a 4.11 gear. He beat me off of the line to the quarter mile where he topped out. I kept on going and whooped him in the mile with my top end. 78 Camaro, 350 4 spd, 3.08 axle.
Nascar is running around a 2.5 ± gear, depending on the track.
Go back Luke.

Originally Posted by mrg325i

The 3.46 will be faster off of the line..

"Theoretically" is the operative term here....some cars (owned by the lucky few) are pure freaks of nature, outperforming 95% of their "identical" brethern....

Originally Posted by mrg325i

The 3.07 has a better top end..

Again, "Theoretically"....

If the 3.46-equipped car spins it up to a more favorable point in the powerband, it WILL by all means take a smoking dump on the 3.07 at the top end.

(Unless you exist in a perfect vacuum, your car will NEVER approach it`s theoretical top speed)

You also have the rev limiter to contend with.
Theoretically, the car should be able to go from 0 - 60 is a specific period of time. You can alter those time by changing the rear gear. We may be talking about 0.2 - 0.4 seconds. Top gear may change 2 - 5 mph.
It made a lot of difference in the Camaro, more hp. I had it stoked up to around 325 hp.

Originally Posted by Fast Bob

One way to be certain is to clock your times with something like a G-Tech Pro....do you have access to one of them ?

Actually, I have one in my glove box. I can't seem to figure it out.

I think part of the problem is my DISA. My car is VERY jerky through the RPM's and sometimes has a massive 4k rpm dip, and sometimes has none at all but feels weak on the bottom end. I think the bell crank lever is totally rounded and the DISA is only working sometimes.

I HOPE a German Auto Solutions kit will fix it. If not, I am may take it to the dealer to have them ship the damn DME to jersey as the local guy who flashed it didn't seem to fix the problem.

Originally Posted by SJBimmer

Car might be slower 0-60 because of the extra shift, but the 3.46 is better for your clutch, and is the better choice for track and general driving.

You think our first gear is not low enough??
I run thru mine faster than I can practically shift and I have the 2.97 rear!

IMHO, i don't think the ZHP needs the 3.46 diff, i think it's perfectly balanced the way it is

Smolck, Your ZHP is probably slower with the 3.46, but I'd bet it's a ton quicker.

You can always compromise and find a gearing in between the 3.07 and 3.46.

Well now, Think of it in a scenario on logical terms. . .Cant break the speed limit so Top end speed will be out of the question since I'm guessing you drive the car daily. So honestly what would be the point of having fast top end speed when theoretically you not only WONT reach it, but You'll get chased by cops (Not that those interceptors will catch you, just saying.) If it were me, I'd use the set up you have with you. I'd rather have a quicker car than a fast one. The odds of me actually using my fast car would be Possibly zero Unless I'm going to the track. (Don't be a Douche). Lastly, Is the difference between 3.07 and 3.46 that much of a difference or is it "negligible"? Would it even matter in a split second Crash or pass While you're in traffic?

The 3.46 will get you from 0 to what every faster than a 3.07 unless there is some internal problem in the differential, that is just simple physics. The 3.07 will give you fewer RPM at the same speed thus saving fuel. If the software limit was not modified, your top end will be the same, you will just be reving higher. If the speed limiter is no longer present, the top end will be higher with the 3.07.

BTW, it was a good visit in Bama, a pleasure to visit face to face. I checked the clutch tool...it's not for 6-speed.