t-5 and speedo gear questions.....

jaidedeye · Dec 6, 2004

i just did my t-5 swap. i have 3.73 gears in my car and the t-5 is a world class with 1988 gear ratio, 3.35 first right?

anyways, i installed a black speedo gear and it seems for the rpms im turning in 5th gear at 60 mph feels like i am going faster. what speedo gear do i need?

now that i have a t-5 my 3.73s feel alot lower than with the aod.

at 60 mph on the speedo i am running 2800-3000 rpm.......does this sound right with my t-5 and 3.73's?

5.0 Nostalgia · Dec 6, 2004

I think you are doing a lot more than 60 if you are turning 2800 rpms. There is a page on the Corral that will tell you how fast you are going. Somebody will probably post the link here. I regret not bookmarking it. I would say you are probably doing about 80 and that engine speed. I think you need the white speedo gear.

squeeeg · Dec 6, 2004

You need either the white gear if you have a 7 tooth drive gear(86-89) or a red gear if you have an 8 tooth gear(90+)

86T-Top · Dec 7, 2004

You need either the white gear if you have a 7 tooth drive gear(86-89) or a red gear if you have an 8 tooth gear(90+)

You got that backwards. You need the red gear if you have the 86-89 trans (yellow drive gear) or the White gear if you have the 90+

Sounds like you need the red gear, thats what I run with my 3.73 and 89 trans with the yellow drive gear.

Mario

joelliott · Dec 7, 2004

I gotta 85gt 5 speed t5. Im putting 3.73 in to replace the stock 3.08s. What color/tooth gear will I need to keep the speedo/ tach right? The above are mentioned 86+. Thanks guys...
I turn 2000 at 80 mph. I have been told an increase in 400 rpms at all speeds for my swap. So Im talkin 2400-2500 rpms at 80 mph. If your turning 2800 rpms, you gotta be going like 90+ mph.
Joe E.

jaidedeye · Dec 7, 2004

ok so do i need a 21 or a 23? my tranny has 1988 gears in it

Michael Yount · Dec 7, 2004

Try this link and see if it helps. Also, did your T5 come out of another Mustang, or was it bought new (a la Ford Racing)? The aftermarket T5Z's have a .625 5th gear as opposed to the Stang's .675 5th - which makes it inaccurate to try and compare speedos/rpms with other Stangs. Also, running different diameter rear tires throws things off too - so if you or any of the folks your trying to compare revs with have different height tires (not uncommon on Stangs) then the comparison won't work. If you're running different than stock height tires, you'll need to take that into account as you're trying to calibrate the speedo. I use mile markers on the Interstate to check the odometer, with a buddy sitting next to me using his watch to check the speedo. Works every time.

http://www.geocities.com/mgnedell/notchback/tech/speedo.html

jaidedeye · Dec 7, 2004

my tranny is a t-5 WC rebuilt by my friend with 1988 gear ratio.

i run 245/50/16 tires on pony rims looks like the red 21 tooth is what i need....but i already have the black 20 tooth.....will 1 tooth make that much difference or should go to the 23 tooth?. my speedo reads about 15-20 mph slower that it should

Michael Yount · Dec 7, 2004

If it's as far off as you say, then something else is different jaidedeye. This is all a matter of ratios. Moving from a 20 tooth to a 21 tooth will affect the speedo only by the amount the ratio of 20/21 - about 5%. If you're sure you're off by 15-20 mph (at what speed? 15-20mph off at 200 mph is only 7.5-10%; at 60mph it's 25-35% off), it's gonna take at least the 23 tooth. The 23 tooth gears are notorious for not lasting very long because the teeth are so small/weak. Probably what it's gonna take is pulling the tail shaft off the tranny, and changing the DRIVE gear from an 8 down to a 7, or from a 7 down to a 6. It's not complex, but on my car, the tranny has to come out to do it. I've done it twice - be sure you use a NEW drive gear retaining clip if you change it out. I tried to reuse the old one, and it came loose requiring another tranny pull, another gear install, AND fishing the old retaining clip out of the inside of the tranny. I'm lucky it didn't get caught up in anything as it migrated from the back of the tranny to the front part - where everything's moving.

jaidedeye · Dec 7, 2004

well like i said before at 60 mph it is running at damn near 3000 rpm.....now if i had 4.10 gears i could see it but i only have 3.73's. should i just buy both the red and white gears and see wich one is the closest?

BlownStangGT · Dec 7, 2004

I have yet to replace my speedo gear, but is the speed actually accurate then when the gear is changed, right now Im 10 off, at 70 im actualy doing 60. Thanks

Michael Yount · Dec 7, 2004

jaidedeye - like I said before, if it's really that far off, neither gear is gonna correct it all the way. You're gonna either need to change the drive gear too, or get one of the speedo conversion boxes. Check with any reputable speedo shop - many people have them. Your speedo cable connects to the box and it connects to the tranny. They have gear reduction inside that allows you to adjust for any error. Without changing the drive or driven gear.

Michael Yount · Dec 7, 2004

edit out double post...

Killercanary · Dec 7, 2004

Here's a link to Hanlon's site for speedo correction. I used this when I had my T5 and now with my TKO. My speedo is pretty much dead on now with my 4.10's.

http://www.hanlonmotorsports.com/t5speedo.asp

Bob also has all the speedo gears needed for the swap.

Michael Yount · Dec 7, 2004

Keep in mind, all the links above pretty much assume that you've got the tranny in the car that came in that particular year/model. If you have a different tranny in the car, or if someone's been inside the tranny, all investigations start by determining which DRIVE gear is in the tranny. The ONLY way to tell with the DRIVE gear on the output shaft is to shine a flash light in the hole (move cable out of the way) and check the color. Black is a 6 tooth; Yellow is a 7 tooth; Green is an 8 tooth. Ford Racing's catalog says that for a 3.73's with stock sized tires, if you have a 6 tooth drive gear, you need the Yellow 18 tooth driven gear; if you have the black 7 tooth DRIVE gear, you need the red 21 tooth DRIVE gear. If your car has an 8 tooth drive gear in it, then you can't get there from here - and you have to either change the drive gear, or go with a black box speed adapter.

jaidedeye · Dec 7, 2004

well usually if the speedo is off it is reading faster right? so wouldnt more teeth slow it down ? in my case i have to speed it up.

Killercanary · Dec 7, 2004

jaidedeye said:
well usually if the speedo is off it is reading faster right? so wouldnt more teeth slow it down ? in my case i have to speed it up.

Hmmm... your right, I missed that before. It does seem as though you be seeing a HIGHER reading than what your speedometer reads given the RPM. I think the first thing you need to do is check like and see what drive gear is in it as Michael said. You may have a 6 tooth in it now. Was it right before you swapped the gears?

Michael Yount · Dec 7, 2004

More teeth on the DRIVEN gear slow the speedo down; more teeth on the DRIVE gear speed the speedo up. Since it's reading MUCH faster, I doubt he has a 6 tooth in there. It's more likely an 8 tooth drive gear, or a very small driven gear if his speeds/tach are accurate.

jaidedeye · Dec 7, 2004

michael.

my speedo is reading slower not faster.

jaidedeye · Dec 7, 2004

so, should i go with a smaller gear like a 18 tooth? this would speed up the speedo right? sux because i just ordered a 21 and 23 tooth gears

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