Why do I have to shift into 4th in 1/8 mile with 4.10's

[MustangLife]

I have 4.10's in my car. And I always have to shift into 4th gear close to the end of the 1/8 mile. If I stay into 3rd, I'm crossing at 6300 rpm's (ouch thats high).

Most people I talk to with 4.10's on sohc stang say they stay in 3rd. But I don't feel good about staying in 3rd at 6300 rpms. My rev limiter is set at 6600. I think I'm trapping 79 -80 mph. I think the lower trap speed is cause of a slow engaging 3rd that I haven't gotten fixed.

mods are in sig.

 

[Bone Racing]

just a guess...do u spin alot off the line?

cause if traction is a serious issue...your 1/4 mile becomes longer and u might add a shift

 

[stangman]

just a guess...do u spin alot off the line?

cause if traction is a serious issue...your 1/4 mile becomes longer and u might add a shift

bingo... if you show us your 60's... we'll most likely show ya why

 

[Jackie Chan]

1/8=stay in 3rd

 

[luther1228]

i stayed in third with 4.30

 

[MustangLife]

Before I broke my rear end I was getting 1.85-1.90 on nittos at lower rpms launches.

Josh

 

[BULLITT#828]

I have 4.10's in my car. And I always have to shift into 4th gear close to the end of the 1/8 mile. If I stay into 3rd, I'm crossing at 6300 rpm's (ouch thats high).

Most people I talk to with 4.10's on sohc stang say they stay in 3rd. But I don't feel good about staying in 3rd at 6300 rpms. My rev limiter is set at 6600. I think I'm trapping 79 -80 mph. I think the lower trap speed is cause of a slow engaging 3rd that I haven't gotten fixed.

mods are in sig.

WHAT?!? Any Mustang equiped with the TR-3650 transmission (2001-1/2 & later) and 4.10 gears (assuming stock height tires) will be travelling at 84.73mph @ 6000 rpms. With your list of mods, I SERIOUSLY doubt your reaching those speeds in the 1/8th mile.

These figure have nothing to do with the amount of wheel spin at the launch, so don't listen to that. If your wheels were still spinning when you went through the traps (fat chance), THAT could effect your need to grap the next gear, but otherwise vehicle speed vs. RPM is only governed by the gear ratios both inside the tranny and the rear end, and the diameter of your rear tires. That's it.

Check out www.bullittarchive.com/Misc/Gears/ for verification.

If link doesn't work, just do a "cut & paste" into your address bar.

Ian

 

[MustangLife]

Well something is wrong. Could it be my 4.10 gear which i got new in box from gef.racing is really a 4.30. I've been thinking thats what it sounds like.

Josh

 

[BULLITT#828]

Josh,

Is your car actually hitting the limiter in 3rd when running the 1/4, or are you just shifting because it looks like you're getting close? Remember, stock tachs are notoriously inaccurate (slightly). You may have up to 200 more RPM's to work with than you think you have. My suggestion: If it doesn't hit the limiter, keep your right foot down.

That is a goog point about your new gears pehaps being mis-packaged, but whoever installed them should have seem the ratio engraved into them. Ask your installer (I'm assuming you didn't did them at home).

Ian

 

[luther1228]

can you run over 110mph in 4th? if so you dont have a 4.30. i never shifted into 4th in the 1/8 with a 4.30

 

[downsouthman1]

Yeah if you're forced into shifting to 4th @ the end of the 1/8th mile you must have like 4.56s.