Will 4:10s mess up a stock T5 ?

Heh heh. OK, that may have been a bit of an exaggeration. I do have about 80K on them right now though, and they're just starting to squeak a bit. Guess it's almost time to upgrade With my other stock geared Fox's I never got more than 30-40K, but with this one and the 3.73's it's pretty fantastic. Just leggo the gas at pretty much any speed is like opening a parachute. I pretty much only ever use it to keep from rolling when I'm already stopped, and the occasional heal/toe around the local exit ramps. I suppose it's either the clutch or the brakes... but I'd rather do an extra clutch every now and then myself. I hate doing brakes. You're right though, I don't use my suspension hard enough. It's really a gross overkill for the street, so it never even brakes a sweat. One of these days when I get the new K-member in and some bigger brakes, I'll take it out to a track day and flog it good and hard... maybe

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Get them!!

I have both the T-5 and 4.10s in my car (which weighs quite a bit more than a Fox Mustang) and they've both held up to numerous runs at the track and some "spirited" driving around town.

Don't fear the gear!!

PhLoBuS said:

if the gears are installed wrong you will get a vibration

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you wont get gear vibration w/ an improper install you will get a whine comming from the gears.

And/or vibration. The gears in my car had been done wrong when I bought it, and at the right rpm and speed there was a pretty impressive vibration right up into the shifter. Rebuilt the rear, vibe was gone. Gears can whine even when they've been done right, the question is just how loud.

Quality gears shouldn't whine if they've been installed correctly; but you'd be surprised the number of folks out there who purport to be 'professional' installers who don't really understand all the details of how to set one up.

Operative word being

Michael Yount said:

Quality

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which is an important clarification. Just as important I think are the other parameters involved, like the condition of the other rear end internals, condition of the case, etc. I haven't observed that many people spring for the extra money to put new parts in when gears are changed, and then they wonder why it still clunks and buzzes. The factory diff in particular has a lifespan, and everybody seems to think that if it doesn't blow it's still ok. Not saying you need to do a new posi just because it's open for a ratio swap, but if there's 100K on it, it should be at least rebuilt if not replaced.

stangbear427 said:

And/or vibration. The gears in my car had been done wrong when I bought it, and at the right rpm and speed there was a pretty impressive vibration right up into the shifter. Rebuilt the rear, vibe was gone. Gears can whine even when they've been done right, the question is just how loud.

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Did you rebuild the rear yourself? I am going to put a set of 3.73's in my car and i want to rebuild my rear end, did u do it, or did you have someone do it for you?

I had 4.10's put in my car a while ago, and I do get a vibration in it...however, I had a Ford Service Tech that does nothing but gear/rear end work install them.

I have an FMS Aluminum driveshaft in it, and I need to take the DS and U Joints to our local shop to have them checked and/or balanced/replaced.

FYI...I get no gear whine at all....it just vibrates at specific RPM ranges.

Hax

i had my entire rear end rebuilt,new bearings, diff clutches, and so on, when i did my gears. i would at least recommend the differential clutches be replaced, it grips really well now.

Lynx331 said:

Did you rebuild the rear yourself? I am going to put a set of 3.73's in my car and i want to rebuild my rear end, did u do it, or did you have someone do it for you?

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I had someone do it. I know my limitations, as does the ASE master tech who turned wrenches with me on every other nut of my car. When there's someone else who can do it better, faster, etc- they get the nod. The guy who built my rear handles all the Eliminator class drag rails in town, I figure he can handle my beater

how much do you think it would cost to get 3.73's installed and the rear end rebuilt as well? I have 130,000 miles on mine, and its 1 tire fire, occasionally with the driver side tire breaking loose.

Lynx331 said:

how much do you think it would cost to get 3.73's installed and the rear end rebuilt as well? I have 130,000 miles on mine, and its 1 tire fire, occasionally with the driver side tire breaking loose.

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Probably the normal $200 for parts and the $300 for labor. But going through a rear-end thoroughly is a different deal. Replacing those wheel bearings is a heck of a job as is the carrier bearings. My guess is about $1000 for the gears, installation kit and install of the gears, rebuild of the axle with new bearings pressed in, and rebuild of the traction lock and including labor.

On the original topic, lower gearing will basically transfer the "stress" on your entire drivetrain from the engine to the rear wheels and rear suspension componenets. It's like the mountain bike theory, your legs are the engine and is what is working hard in that 5th gear to get up that hill and all that stress placed upon your chain would be the rear suspension. The less the car is able to move with more power added from the engine, then the more stress and bind you create - that force right there is what blows a tranny or the rear-end. Lowering gearing will alleviate that stress with regards to one condition, if all that extra "gear torque" that has been newly mulitplied at a greater level on the wheels is allowed to be transfered to the ground and therefore get the car moving. If the wheels don't turn freely (for example: the use of extra sticky slicks and some great power-transferring control arms) then you have that much more stress on your drivetrain with a destructive force waiting to break something. The entire reason for such components breaking (for those nonbelievers) is because you have all this built up force in a bind looking for a place to go - where it goes is the weakest point in the drivetrain. Once it finds it, if the force is great enough (and not released yet by the wheels turning fast enough to relieve the amount of force it needs to) it will break that component in the process of trying to release this built up energy/force somewhere but not where it is supposed to (the wheels and then to the ground).

Hope that is a simple enough explanation, sorry for the long post.

That's it! That's it! That's what I was trying to say! I need to just leave some of this stuff alone, there's always someone who eventually comes along who can say what I want to, only better.
TNX

stangbear427 said:

That's it! That's it! That's what I was trying to say! I need to just leave some of this stuff alone, there's always someone who eventually comes along who can say what I want to, only better.
TNX

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Yeah there are a lot of people that know exactly what they mean and know how things work and why they do in their heads but just can't put it in explanatory form. I seem to be one of those people half the time myself, glad I could get it out in the words you were looking for