swap from 3.73's to 3.55's???

[04sleeper]

3000 RPM at 60 MPH? How tall is your rear tires?

Traction will be an issue even with a lower ratio gear. I had more of a traction issue with 308's then I do with 373's.

If you have all the gear ratio's of each gear in your tranny, along with the tire height, then you should be able to calculate what different gears will do for your car.

Michael Yount seems to be very good with these numbers.

Maybe he will chime in and help.

 

[jaidedeye]

i currently have 3.73 gears in my car, i have the low gear set in my t-5. im thinking about swapig to 3.55's. here are the reasons, HWY travel, i run at about 3000 rpm on the highway at 60 mph, also i have huge traction issues with 3.73's......any suggestions? maybe other gear suggestions?

 

[5.0 Nostalgia]

3000 RPMs at 60? That doesn't sound right. Are you in 5th?

 

[NKau]

I think he meant to say 2,000 rpm at 60 mph? In either case, dropping from the 3.73 to a 3.55 isn't going to amount to much of an rpm difference. You'd have to go to a 3.27 or something similar to get a significant drop.

 

[jb89coupe]

I'm going to assume you meant 2000rpm @ 60mph (if not you should try using 5th gear ). With my 3.55's 2000rpm is about 65mph, so there's really not much of a difference. 3.27's are an option but you'll feel you car start to get sluggish the lower you go. imo a 3.73-3.55 swap (or vice versa) isn't really worth the money or effort.

 

[5spd GT]

If you have the money and don't mind spending it to the lower the cruising rpm a bit...go for it...

I guess you meant 2000rpm...or are you sure you have 373 gears (bought it used?)...

 

[jaidedeye]

no seriously, i meant 3000 rpm in 5th @65

the gears were in the car when i bought it. but, it had an AOD in it. so the gears didnt feel as aggressive. now with my t-5 the gears feel like more than 3.73's i hang out with the guy i bought it from, it was his brothers car. hell maybe im talking out my but and actually have 4.10's....can i pull my inspection plate off y rear end and look on the ring gear ???? or count the teeth?

 

[Grn92LX]

Jack the back of the car up and count how many times the driveshaft spins to every 1 revolution of the wheel. This IS your gear ratio. For example if the Dshaft spins 3 1/2 times you have a 3.55. If your doing 3k in 5th at 65 you have a steep gear and a short tire. I do about 2200 in 5th at 65 with 25.5" tires. 410's would make that about 2400rpm.

 

[NKau]

Either you have 4.56's, or your tach is way off You can check the gear ratio without even pulling the diff cover. Jack up the rear of the car and put it on jackstands and chock the front wheels. Put the tranny in neutral. With a chalk marker, put a mark on the bottom of the driveshaft and a mark on the bottom of one of the rear wheels. With someone turning the marked wheel one full revolution, count the number of times the driveshaft turns. If the DS turns a hair over 4 times to one time the wheel turns, you have 4.10's, etc. Good luck, and let us know what you find.

 

[jb89coupe]

It sounds like don't have 3.73's AND your speedo is way off. According to the corral gear calculator, you'd need a 5.18:1 rear end ratio to do 65mph @ 3000rpm with stock sized tires.. with a stock t5 5th gear. Check to see what your rear ratio is using the method above, then make sure you have the right speedo drive/driven gears. Sounds like you may have 4.56's, because with 3.73's @ 3000rpm you'd be doing like 90. I'm sure you'd notice that you're whipping past traffic (or maybe you just through everyone else drove really slow this whole time?).. Good luck

Edit: with 4.10's you should be doing around 82mph @ 3000rpm. with 4.56's it should be around 74. Again these results are with stock tire size and a stock t5 5th gear.. according to a gear calculator, so factor in some error/wind resistance.

 

[jaidedeye]

well i have a black speedo gear......if my speedo is in fact slow....should i go with a smaller speedo gear?

 

[Grn92LX]

well i have a black speedo gear......if my speedo is in fact slow....should i go with a smaller speedo gear?

No! Your first step is finding out what the hell you have in your rear end. Do what myself and NKau suggested and report back.

 

[jb89coupe]

The black gear is a 20 tooth driven gear.. in an 89 or earlier t5 the 20 tooth is for 3.55's, 90+ t5 uses that gear for 3.08's. I think if you have a 90+ you need to change the drive gear too to get it calibrated right.
My point in the last post was that I think you could tell the difference between 60mph and 90mph, so I really don't think you have 3.73's anyway. Check to make sure first.

 

[jaidedeye]

my t-5 came out of an 89 g originally.

im going to check my gears tomorrow.

here is what bothers me though......ok, if i do infact have more than 3.73's, with a 20 tooth drive gear wouldnt my speedo read too fast? the car i got my tranny out of had 3.55's in it and he said the speedo was dead on.

 

[jaidedeye]

No! Your first step is finding out what the hell you have in your rear end. Do what myself and NKau suggested and report back.

whats your problem dude? im just asking questions.....im trying to figure out all the possible causes could be......

 

[NKau]

my t-5 came out of an 89 g originally.

im going to check my gears tomorrow.

here is what bothers me though......ok, if i do infact have more than 3.73's, with a 20 tooth drive gear wouldnt my speedo read too fast? the car i got my tranny out of had 3.55's in it and he said the speedo was dead on.

Your speedo should in fact read a bit fast, but I wouldn't be suprised if it was off by 5 mph or so anyway. My guess is that your tach might be way off too, but we really can't tell until you find out what your actual approximate gearing is.

 

[jb89coupe]

You're right, it would read fast. I guess the other option (as mentioned already) is that your tach is 1000rpm off, but that's pretty scary. If I were you I would check and make sure what gears I have then take it from there. If you do in fact have 3.73's then you should get the right driven gear (21 tooth/red) and an aftermarket tach. The speedo gear will only account for ~5mph difference, so your tach still must be way off to be reading 3000rpm @ 60mph.

 

[jwzg]

whats your problem dude? im just asking questions.....im trying to figure out all the possible causes could be......

Grn92LX is a bit less than tactful at times. Bear with him here. He's just trying to get you to do first things first.

 

[Grn92LX]

whats your problem dude? im just asking questions.....im trying to figure out all the possible causes could be......

I don't have the problem, you do. Your the one that rev's @ 3000 rpm with your mysterious 373 gears, not I I'm just trying to get you to do the right thing and find out WTF you have in the read end so we can diagnose your issue. I told you the FIRST and FOREMOST thing you should be doing. Don't mistake my common sense for an attitude, thanks.

Thanks jwzg.

 

[hllon4whls]

I agree your priority is to find the true ratio.

Are you sure that your tranny is an overdrive in 5th?

You can check all of this with a jack and a few hand tools.

Mark a scratch or chaulk line on the driveshaft and on the tire. With both tires off the ground, Turn the drive shaft untill the tires make one revolution. Count the turns on the drive shaft makes. 3 1/2 = 3.55. Just over 4= 4.10 4 1/2 = 4.56. Hard to write, but I believe you get the idea.

To check the tranny ratio, mark the driveshaft and the balancer. Turn the motor 1 turn. The driveshaft should turn more than 1 rotation if you have an OD tranny. (Tires off ground, tranny in 5th). The factory T5 has an approximate ratio of .67:1. If I calculate this correctly, you should get 1.49 turns of the driveshaft to one turn of the balancer in OD.

This will help us to help you. You and we both need to get a starting point so that we can find the appropriate solution. We can offer the advice and you have to do the grunt work or chose to figure it out on your own.