4.56 or 4.30

RE: 4.56 or 4.30

Besides the regular installation kit, your differential will need a notched cross pin for clearance of the taller gears. Of course it goes without saying some type of traction-lock differential would be preferred to prevent one-tire fires. ;)
 
RE: 4.56 or 4.30

why so much gear? 4.10's with a good stall is plenty, and you can still drive down the highway.
 
RE: 4.56 or 4.30

[div class="dcquote"][strong]Quote[/strong]
... 4.10's with a good stall is plenty, and you can still drive down the highway.
[/div]

I've actually considered changing to 4.30s to tweak a better 60 foot time but I am hesitant due to the impact on the highway diving since I would like to continue driving the car to the track(if I didn't, I'd go with 4.56s w/ no question).

BUT, I have been thinking... it would only increase my cruising RPMs by about 200 rpm, so couldn't I just have the IMRC cut-in speed changed on the chip by 200 rpm? ::uh::
 
RE: 4.56 or 4.30

[div class="dcquote"][strong]Quote[/strong]
BUT, I have been thinking... it would only increase my cruising RPMs by about 200 rpm, so couldn't I just have the IMRC cut-in speed changed on the chip by 200 rpm? ::uh::
[/div]

Not on a EEC IV car ...

You would have to modify the harness and incorporate a window switch, or simply deactivate the IMRCs for the trip, but remember they are open with no VAC.
 
RE: 4.56 or 4.30

[div class="dcquote"][strong]Quote[/strong]
[div class="dcquote"][strong]Quote[/strong] BUT, I have been thinking... it would only increase my cruising RPMs by about 200 rpm, so couldn't I just have the IMRC cut-in speed changed on the chip by 200 rpm? ::uh:: [/div]Not on a EEC IV car ... You would have to modify the harness and incorporate a window switch, or simply deactivate the IMRCs for the trip, but remember they are open with no VAC.
[/div]

Arrrrrrrrggh... every once in a while this is where I like the OBD-II vs. the EEC-IV. :B
 
RE: 4.56 or 4.30

[div class="dcquote"][strong]Quote[/strong]
[div class="dcquote"][strong]Quote[/strong]... 4.10's with a good stall is plenty, and you can still drive down the highway.[/div]I've actually considered changing to 4.30s to tweak a better 60 foot time but I am hesitant due to the impact on the highway diving since I would like to continue driving the car to the track(if I didn't, I'd go with 4.56s w/ no question). BUT, I have been thinking... it would only increase my cruising RPMs by about 200 rpm, so couldn't I just have the IMRC cut-in speed changed on the chip by 200 rpm? ::uh::
[/div]

The torque and engine efficiency curves cross at 3000 rpms, so changing the IMRC cut-in only works to make the engine less efficient.

The only reason to change IMRC cut-in is with significant modification to the engine (intake, blower, etc.) - anything that would change the airflow characteristics. Headers might even warrant it, but definitely not gearing.

Cruising with the IMRCs open for long periods of time should not negatively affect the engine in anyway. I'm sure there are some guys who have done the IMRC delete that can speak to this.
 
RE: 4.56 or 4.30

[/div]The torque and engine efficiency curves cross at 3000 rpms, so changing the IMRC cut-in only works to make the engine less efficient.The only reason to change IMRC cut-in is with significant modification to the engine (intake, blower, etc.) - anything that would change the airflow characteristics. Headers might even warrant it, but definitely not gearing.Cruising with the IMRCs open for long periods of time should not negatively affect the engine in anyway. I'm sure there are some guys who have done the IMRC delete that can speak to this.
[/div]

imrc deletes just moves your torque range up to the higher rpms.
 
RE: 4.56 or 4.30

[div class="dcquote"][strong]Quote[/strong]
imrc deletes just moves your torque range up to the higher rpms.
[/div]

I have Kooks 3/4 length headers, 4.10s and I am currently exploring intake options, one of which is a gasket matched, ported and polished Gen1 intake. I am also considering moving to 4.30 gears. With a 3500 stall converter, what is my best course of action for best performance on the track but retaining best streetability when it comes to highway driving?

IMRC delete?
Cobra intake?
4.30 gears?

Any combination or all of the above?
 
RE: 4.56 or 4.30

[div class="dcquote"][strong]Quote[/strong]
[div class="dcquote"][strong]Quote[/strong]imrc deletes just moves your torque range up to the higher rpms. [/div]I have Kooks 3/4 length headers, 4.10s and I am currently exploring intake options, one of which is a gasket matched, ported and polished Gen1 intake. I am also considering moving to 4.30 gears. With a 3500 stall converter, what is my best course of action for best performance on the track but retaining best streetability when it comes to highway driving?IMRC delete?Cobra intake?4.30 gears?Any combination or all of the above?
[/div]

Easy...the TC enables you to discard the IMRCs with no issue what so ever.

The Cobra intake is also a good choice, but if your tranny and chip are already setup for the 4.10's, it is probably not worth the hassle or expense (speedo gear, chip reburn) to go to 4.30's. The marginal increase won't do much on the time slips.

I am running a 3000 stall converter with stock gearing (3.07) and an Eaton posi and I can still easily spin the tires at launch.

Unless you plan on putting 285 wide drag radials on the back, the 4.10 gearing is more than adequate.
 
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