question about gears in machs
- Thread starter Got Boost?
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GrimlokTT said:
never...only for racing....
GrimlokTT said:
I used a standard set of 8.8 carrier bearings, shims, crush sleeve, and pinion seal. I used a cast iron housing from a '95 Thunderbird, because it was on hand, but if you use an aluminum housing it will need to be spread with a case spreader (driving the carrier shims in will damage the aluminum case). If you want to change the side seals and bearings at the stub axles, order the FRPP IRS stub axle bearing and seal kit (M-4413-A), it is best to do this while everything is apart instead of deciding to do it later.
I was thiinking of getting 4.10's but after reading for a while, i decided that i will go with 4.30's. Just seems like the best gear for DD/racing
mustangmach04
Banned
come on guys with the school terms, its summer for christ sakes, i am not looking foward to going back to classes.
Good choice, at first I thought it was too low of a gear, but I took a chance and I have never regreted it. :thumbsup:instantmassege said:
I plan on Procharging and only running DR's at the strip so I am getting 4.10's....
Sig is correct.wurd2 said:
I'm runnin' the FRPP 4.56s. I love them and wouldn't have it any other way. Great gear for a non-boosted car.
Highway 80mph = 3000rpms
And I can actually use 5th gear around town now
Highway 80mph = 3000rpms
And I can actually use 5th gear around town now
wurd2 said:
He means you'll have to shift into 4th right at the traps with 4.10 gears. :loser:
viperbluelx said:
Assuming a Mach1 has the stock Tremec transmission and a stock tire size (or comparable) in the rear, 3rd gear at 6800 RPM is 96.00 MPH with 4.10's and 91.54 MPH with 4.30's. And since a stock Mach1 engine typically stops making good power in the 6200 RPM range, shifting at 6800 RPM and beyond is not ideal. So given the above assumptions, 3rd gear at 6200 RPM is 87.53 MPH with 4.10's and 83.46 MPH with 4.30's. In light of these facts and assumptions, stating that you'll have to shift into 4th gear before the traps isn't exactly stating much, now is it?
:burn:
I shift into 4th with stock gears
Mach1chuck said:
Chuck,
I'm not sure I understand, here. You said 4.10s weren't low enough so you stepped it up to 4.30s. Now, you are putting in 3.90s...?
I'm looking for a gear to get my car in the powerband quicker but still'd like it daily driver friendly and use 1st gear every time.
Thoughts?
Aaron
It doesn't sound logical to me either. I liked the 4.30s best with the straight axle, but I had to use 5th a lot more than I did with the 3.55s. The 4.10s felt like the car was lugging in 5th, but revved higher than I liked for normal use in 4th gear. The 3.90s work for me because I'm staying in 4th, instead of shifting to 5th as much as with the 4.30s. The revs are only a little higher, turning a couple hundred rpms more than with the 3.55s that were in the IRS when I first installed it. A side issue for me was the desire to avoid making so much torque at the wheels that traction problems came up everytime I stepped on it hard, since I don't want to rework the IRS for drag racing. The 3.90s are 9% lower than the 3.55s, so they will get into the powerband quicker, but if you want maximum acceleration the 4.30s or 4.56s work very well. I actually am planning a '00 Cobra R six speed swap at some point in the future, so with the 3.90s I will still have approximately the same torque multiplication as 3.55s with the five speed.
So, it sounds like you recommend 3.90s for my use, correct?
The 3.90s are good daily driver gears, they let you run 1st gear through an intersection, instead of needing to change gears 3/4 of the way through. I am well pleased with mine so far. Since you and I are now running Cobra IRS units, it is safe to say that drag racing isn't part of the plan for us. 4.10s or 4.30s are fun gears with a solid axle, but the level of torque multiplication with 4 series gears would make it harder to avoid wheel hop with an IRS, leading to the need to do a fair amount of other upgrades. I actually considered 3.73s, since I was building up a bare pumpkin, but decided that there wouldn't be a noticeable improvement with 3.73s. All I would have really gained then would be the gear type limited slip (Detroit Truetrac). A note on the 3.90s, though, since they aren't FRPP gears there will be more to setting them up than the popular "swap the factory shims onto the new gears" method of setting up the gears. This is one reason for the popularity of the FRPP gears, even though FRPP gears should be set up at correct pinion depth for that particular set of gears. Many people use the stock shims and hope for the best, but setting the pinion depth with a pinion depth gauge and checking the pattern are vital with aftermarket gears.
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3.90 Gear update
The 3.90s have been in for about eight or nine days now. I finally ran the car hard after a one week break-in of the gears. The performance of the Mach1 with this gear set is impressive. The combination I am running is a 3.90 gear set on a Detroit Truetrac 31 spline differential in a cast iron Thunderbird pumpkin in an '03 Cobra IRS. The traction is excellent with this combination, and I haven't experienced wheelhop even when traction was marginal. I believe that the torque splitting capability of the Truetrac and the weight (inertia) of the iron T-bird pumpkin helps to reduce or damp out any perceptible wheel hop. I had a friend ride with me on one run who said that it felt stronger than with the 4.30s, mainly because traction wasn't as much of a problem with the 3.90s as with the 4.30s. I have never had any timed runs with any of the different gears (3.55s, 3.90s, 4.10s, and 4.30s) that have been in this Mach1, so I can't say for a fact that the 3.90 gears will run a quicker time than other gear ratios, but the performance with 3.90s doesn't disapoint me in any way.
The 3.90s have been in for about eight or nine days now. I finally ran the car hard after a one week break-in of the gears. The performance of the Mach1 with this gear set is impressive. The combination I am running is a 3.90 gear set on a Detroit Truetrac 31 spline differential in a cast iron Thunderbird pumpkin in an '03 Cobra IRS. The traction is excellent with this combination, and I haven't experienced wheelhop even when traction was marginal. I believe that the torque splitting capability of the Truetrac and the weight (inertia) of the iron T-bird pumpkin helps to reduce or damp out any perceptible wheel hop. I had a friend ride with me on one run who said that it felt stronger than with the 4.30s, mainly because traction wasn't as much of a problem with the 3.90s as with the 4.30s. I have never had any timed runs with any of the different gears (3.55s, 3.90s, 4.10s, and 4.30s) that have been in this Mach1, so I can't say for a fact that the 3.90 gears will run a quicker time than other gear ratios, but the performance with 3.90s doesn't disapoint me in any way.
Thank you for the update. What brand gears did you go with? Is there any noise from your rear? Why did you go with the Truetrac? Did you do the install?
Sorry for all the questions. I'm a newb at this.
Sorry for all the questions. I'm a newb at this.
just added the 4:30's and 31 spline axels on my mach. love them and the tear ass down low and still pull up top. they are the way to go.
Grenade
Banned
I love my 410's a great all around gear, And I have room for a power adder, in case I want to trap in the 120's. Now I trap 109, and I shift at 6200. plenty before the end of the 1/4. I start off in first gear like any other car. Its only 15% different. But first and second rock.
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