Which gear? Not usual question I promise!!

[BullittAndy]

91 LX with H/C/I with 100hp nitrous.
I've got 4.10's now. I've always had a vibe from the rear end, used to be BAD now its tolerable (normal solutions). I've developed some rear end noises recently along with needing the trac loc to be rebuilt.

Now, I've read about the "critical speed" being higher with stock gears and how higher gears can cause vibration.

I hate the vibes in my car and since I need the rear end to be "gone through"
I'm thinking of changing the rear gears to 3.55's in order to raise the "critical speed."

Will I be sorry going from 4.10's to 3.55's?

Should I expect the vibes to go away?

 

[86bluecobra]

Is this a automatic car or a 5 spd car? If its an auto then yes you will notice and be sad with the gear swap if its a 5 spd car then it should be fine. You might even get some use back out of first gear.

 

[BullittAndy]

It is a 5 speed and I didn't think about the 1st gear issue. Thanks.

Anybody else?

 

[blackened88lx]

if its a 5 spd car then it should be fine. You might even get some use back out of first gear.

Agreed. Unless it's dead hooking on the street, the first couple gears must be useless right now.

 

[cenok is family]

i LOVE my 4.10's, but if i had h/c/i and a 100 shot, i'd probably gear it a little higher. i wouldn't be able to drop all the way to 3.55's, i'd probably go 3.73s. but that's just me.

 

[Foxfan88]

if you have enough power the less you will be able to feel the difference b/w ratios, unless you go the the extreme like going from 4.10s to 2.73s you could feel that i am sure but a small change like 4.10 to 3.55 wouldnt feel any different.

cenok i think you would be fine going to 3.55s from 4.10s if it did lose a little sotp feel ( it would be small) it would more than gain it back in, highways rpms, driveabilty (less shifting/easier to drive) and each gear would be longer. going to high of a gear will be killer down low but before you know it the cars already done at around 100 mph

i am running 3.90s with a z spec t5 in my car and since i added my SC, with just a mild 5 psi its got all sorts of traction issues now, it hooked good before, but now its just frying the tires in first and all the way through second. and i mean burning rubber not just squealing them a bit

my rearend is getting a little tired, its starting to do the one wheel peel sometimes i am thinking of going back to 3.55s or something to get some use out of first. its got the power but with the lower gear its just spinning the crap out of the tires and it sucks. plus with the low gear its gone through 4th gear at a little over 100 and its done. i dont want to hotrod it in 5th, no point there.
with 3.55s i doubt i would lose any sotp feel. if it did lose a tad bit it would drive better and gears would go longer which is worth it to me. may even feel faster since it would be in boost more instead of roasting the tires through the gear.

what i am saying is gears IMO dont make as much difference on a modded car. on a stock mustang that make a big difference because a bone stock 5.0 isnt very powerful and undergeared from the factory it really limits what the engine can do a set of gears make it better.

but i've driven/rode in alot of difference mustangs. some with similar mods, some with different mods, all difference gear ratios and honestly i cant tell a difference at all on what gears they are running by sotp feel.you could maybe guess by how the gears act. how long they last and etc. but then again difference mod and combos have an affect on how fast and engine will rev up and whatnot.. i can tell when a mustang has stock gears but if its anything lower than 3.55s it feels the same. going higher than 4.10s you would probably tell because the gears would be short but anything int he 3.55 to 4.10 range feels the same to me sotp wise.

 

[cenok is family]

if you have enough power the less you will be able to feel the difference b/w ratios, unless you go the the extreme like going from 4.10s to 2.73s you could feel that i am sure but a small change like 4.10 to 3.55 wouldnt feel any different.

cenok i think you would be fine going to 3.55s from 4.10s if it did lose a little sotp feel ( it would be small) it would more than gain it back in, highways rpms, driveabilty (less shifting/easier to drive) and each gear would be longer. going to high of a gear will be killer down low but before you know it the cars already done at around 100 mph

i am running 3.90s with a z spec t5 in my car and since i added my SC, with just a mild 5 psi its got all sorts of traction issues now, it hooked good before, but now its just frying the tires in first and all the way through second. and i mean burning rubber not just squealing them a bit

my rearend is getting a little tired, its starting to do the one wheel peel sometimes i am thinking of going back to 3.55s or something to get some use out of first. its got the power but with the lower gear its just spinning the crap out of the tires and it sucks. plus with the low gear its gone through 4th gear at a little over 100 and its done. i dont want to hotrod it in 5th, no point there.
with 3.55s i doubt i would lose any sotp feel. if it did lose a tad bit it would drive better and gears would go longer which is worth it to me. may even feel faster since it would be in boost more instead of roasting the tires through the gear.

what i am saying is gears IMO dont make as much difference on a modded car. on a stock mustang that make a big difference because a bone stock 5.0 isnt very powerful and undergeared from the factory it really limits what the engine can do a set of gears make it better.

but i've driven/rode in alot of difference mustangs. some with similar mods, some with different mods, all difference gear ratios and honestly i cant tell a difference at all on what gears they are running by sotp feel.you could maybe guess by how the gears act. how long they last and etc. but then again difference mod and combos have an affect on how fast and engine will rev up and whatnot.. i can tell when a mustang has stock gears but if its anything lower than 3.55s it feels the same. going higher than 4.10s you would probably tell because the gears would be short but anything int he 3.55 to 4.10 range feels the same to me sotp wise.

yeah i know what you mean. i've just always been skeptical about 3.55's cause i rode in a 5 speed car with 3.55's that had some other bolt ons and it wasn't very fast. of course his car never really ran that great anyway.

 

[Foxfan88]

yeah i was kinda the same way, i used to think that you HAD to get no less than 3.73s or the car would be slow . i rode in a guys mustang, it had some minor bolt ons was all and it had 3.55s it was a nice car, wasnt really fast seeing it was pretty much stock but it sure as hell felt alot faster than what it was with him driving it, he was a good driver, shifted good an real fast and just knew how to drive the car well. i liked how it had the sotp boost a bit but had great street manners and it didnt feel like 1st only went to 25 mph lol, just felt like a good mix of driveability and performance.

IMO the driver and the actual power of the car determines how fast the car is over gears.

when i put my gears in my car, i liked the change but it didnt feel like real "power" gain. i liked my t5 swap and SC install more in terms of power. the t5 did some gear ratio changes but there was more power getting to the ground and a solid connection to the rear wheels which made it snappier and better. the car acted the same RPM wise and etc , but it just made more power and went faster.

same with the SC the car acted the same RPM wise it just added more power which was better.

where the gears it didnt feel like a power increase, it felt like i stuck a 10 speed bike into low and started pedeling, it was easier to get up the speed and stuff but the top end lacked, same with the car, excellent low end but it didnt have the same top end feel, runs out of gear fast. didnt feel like power it just felt like it sped up the rpms, its the same power output as before but its like speeding it up like fast fowarding a tv lol

i liked my gear swap but it wasnt too impressive, it helped but nothing like people said it would.

heres a scenario take two similar cars, one with 2.73s and one with 3.73s and they are road racing and come up on a long straight away. the 3.73 car will outrun the other car at first, will gain speed faster but it will hit a wall where it get outs of its powerband and cant really go any faster and has to keep going one speed. while the 2.73 car is starting out slower but will pass his opponent and keep on going b/c he is still in his powerband making power and hasnt run out of gear yet, if the straight away is long enough the 2.73 car would get to the next turn first assuming they were even going into the straight away

of course this if for a road racing deal but for a drag racing deal you want the lowest gear possible that will put you at the traps at the very end of your last drive gear, so for a mustang it would be your redline or peak HP rpm in 4th gear. with my 3.90s my car crosses the line at 5500 in 4th

works good for the track but if i get into a street race or something with similar power and a higher gear like 3.55s or something, i would probably out run in down low and stay ahead, but if the race goes much past 110-115 mph my car is done and throwing in the towel and i will be passed by the other car b/c he still has gear left. he may be just shifting into 4th and has a whole other gear left to keep accelerating in. sure we could use 5th but its used for highway cruising not racing IMO. at speeds where your trying to use 5th to go faster wind resistance is just going to work against you and its just a waste of time IMO

this is why i am strongly considering a swap to 3.55s my car pulls hard down low. makes enough power to where it just spins the tires like crazy. since i am planning on a tune and more boost (8-10 psi) it would only make tire spin worse. i see 3.55s a better choice, i doubt it will make tirespin go away, 8-10 psi on my engine will probably spin them whatever gear i go with but i see it helping and make the car better to drive and still make good power and pull hard and have the ability to go faster than 100 or so and having to let out of it. i am not a top speed freak but knowing that you can makes it better lol

sorry for the wall of text i get into a habit of doing that lol