Speedometer driven gear
Thread Starter
|
Elder User
Joined: Aug 2011
Posts: 649
Likes: 1
From: Tucson, AZ
Speedometer driven gear
Hi guys,
I have *about* an 89 rebuilt T5 WC transmission with an S-10 tail housing. It has the speedometer drive gear in the right spot etc. (I can see it through the driven gear mounting hole). But I don't know how to go about finding the right driven gear/cable etc. There are several available on the internet, but with different tooth counts and whatnot. Any help?
Tyler
I have *about* an 89 rebuilt T5 WC transmission with an S-10 tail housing. It has the speedometer drive gear in the right spot etc. (I can see it through the driven gear mounting hole). But I don't know how to go about finding the right driven gear/cable etc. There are several available on the internet, but with different tooth counts and whatnot. Any help?
Tyler
Laughing Gas
Joined: Jun 2011
Posts: 1,041
Likes: 53
From: Sterling CO
what's your rear end ratio and tire size?... probably the easiest thing to do is to go to a local trans shop like AAMCO and give em the parameters and they can give you the part number and price - should be a shelf part for $18
[edit] 2 other questions What did the the trans come out of?, and is it a wide ratio or narrow ratio?... dozens of T-5's out there, some with 7 tooth drive gear and 8 tooth - as you have probably found out you can buy driven gears in just about anything.
[edit] 2 other questions What did the the trans come out of?, and is it a wide ratio or narrow ratio?... dozens of T-5's out there, some with 7 tooth drive gear and 8 tooth - as you have probably found out you can buy driven gears in just about anything.
Laughing Gas
Joined: Jun 2011
Posts: 1,041
Likes: 53
From: Sterling CO
oooh I have to correct myself - didn't know about this one - there is also a 6 tooth drive available...
colors for the DRIVE gear are:
black 6 tooth
yellow 7 tooth
green 8 tooth
so might be just as fast to look at the drive gear (take the driven out, drive is the one on the shaft) and see what color the drive is.
colors for the DRIVE gear are:
black 6 tooth
yellow 7 tooth
green 8 tooth
so might be just as fast to look at the drive gear (take the driven out, drive is the one on the shaft) and see what color the drive is.
Thread Starter
|
Elder User
Joined: Aug 2011
Posts: 649
Likes: 1
From: Tucson, AZ
Brian (is that right?),
Mine is red. The stuff I've seen on he internet indicates 15, 17, 18 and 19 tooth. I'm just starting to delve into this so my info may be way incomplete, but that's what I've seen do far.
I know my diff is a 2.79. That's all I've got right now.
I don't even know what the driven gear is supposed to look like. And what the housing for it and the cable and all that looks like. Or how it attaches to be trans.
Best, Tyler
Mine is red. The stuff I've seen on he internet indicates 15, 17, 18 and 19 tooth. I'm just starting to delve into this so my info may be way incomplete, but that's what I've seen do far.
I know my diff is a 2.79. That's all I've got right now.
I don't even know what the driven gear is supposed to look like. And what the housing for it and the cable and all that looks like. Or how it attaches to be trans.
Best, Tyler
Laughing Gas
Joined: Jun 2011
Posts: 1,041
Likes: 53
From: Sterling CO
warnig this is NOT a T-5 picture (it's a corvette)
in this picture the DRIVE gear is green, the DRIVEN gear is grey.
You never replace the drive gear unless it is shot or you are rebuilding - you change out the driven to get your speedo right.
90% of speedometers I believe want a 1000 revolutions to the mile to be accurate, so when you change out rear ends and/or tires you have to change out the driven gear or your speedo will be inaccurate.
There are speedoes that want other numbers besides 1000, most common I think are 940, 960, 1050.
you got to know all factors before you spend any money on new driven gears. so if you don't have a tire size chosen yet then don't worry about this step till tires are bought and set in stone.
in this picture the DRIVE gear is green, the DRIVEN gear is grey.
You never replace the drive gear unless it is shot or you are rebuilding - you change out the driven to get your speedo right.
90% of speedometers I believe want a 1000 revolutions to the mile to be accurate, so when you change out rear ends and/or tires you have to change out the driven gear or your speedo will be inaccurate.
There are speedoes that want other numbers besides 1000, most common I think are 940, 960, 1050.
you got to know all factors before you spend any money on new driven gears. so if you don't have a tire size chosen yet then don't worry about this step till tires are bought and set in stone.
Fleet Owner
Joined: Jul 2004
Posts: 27,283
Likes: 1,046
From: NM
Wow. I can't think of any T5 application where there was a rear axle that low. S-10's had either 3.90 or 4.10 rears. I think Mustang GT's were down to 3.25, with probably smaller diameter tires than your truck. You may have to use a speedo correcting adapter: Speedometer Ratio Correction
You could just buy any T5 driven gear, measure how far off you are, and order an adapter to take care of it.
You could just buy any T5 driven gear, measure how far off you are, and order an adapter to take care of it.
New User
Joined: Oct 2013
Posts: 24
Likes: 0
Im sure someone who has done the swap before will chime in. There must be thousands of people who have already did it successfully.
Trending Topics
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
There are some situations where there will be no driven gear available to get an accurate speedometer reading. My previous truck had a 2:26 Chrysler rear gear and with a TH350 transmission, the closest I could get with a driven gear was 10 MPH off. I was able to live with that but the correcting adapter seems like the way to go here....
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Laughing Gas
Joined: Jun 2011
Posts: 1,041
Likes: 53
From: Sterling CO
I always just used a chart, but the math is actually easier
you have to know 4 out of 5 variables (and I think Tyler hasn't decided 1 under his control yet that must be known before the formula can be used)....
Here's one of a dozen formulas posted on the net:
# Drive Teeth x Axle Ratio x Tire Rev. per Mile / 1001 = # Driven Teeth
instead of 1000 or 1001, you put in *what your speedometer wants* - (as I said typically 1000, sometimes 940, 960, 1050, etc) look at the back of your speedo or find the manual.
you have to know 4 out of 5 variables (and I think Tyler hasn't decided 1 under his control yet that must be known before the formula can be used)....
Here's one of a dozen formulas posted on the net:
# Drive Teeth x Axle Ratio x Tire Rev. per Mile / 1001 = # Driven Teeth
instead of 1000 or 1001, you put in *what your speedometer wants* - (as I said typically 1000, sometimes 940, 960, 1050, etc) look at the back of your speedo or find the manual.
Laughing Gas
Joined: Jun 2011
Posts: 1,041
Likes: 53
From: Sterling CO
T-5 driven gears can be bought in literally just about every odd number you can think of even all the way up to 23 (several people caution against using a 23 though the teeth are paper thin and you end up replacing the gear about every 20k miles).
Laughing Gas
Joined: Jun 2011
Posts: 1,041
Likes: 53
From: Sterling CO
As for measuring how far off you are, let me throw out how I did it. user you smartphone download a backpacking app like trackker that measures distance covered and is very accurate - like to the foot accurate. Go out in the country and reset the odo, start the fone app - see how much the odo rolls over as you slowly and consistently drive exactly 1 mi to the letter. a sample size of 1 mi gets you pretty darn close, as close as you are gonna get jumping whole teeth sizes. If you want to find out how far off you are by law of averages, take a road trip out on the highway some slow day and measure how close you can get over a 10, 20, or 100 mile distance... if you cover 99 odo miles in 100 gps then you are 99% accurate off by 1%.
Tyler you say your gear is red - that is the DRIVEN gear right... when you take it out and look down in the hole at the shaft and the DRIVE gear, what color is the DRIVE gear?
Tyler you say your gear is red - that is the DRIVEN gear right... when you take it out and look down in the hole at the shaft and the DRIVE gear, what color is the DRIVE gear?
Laughing Gas
Joined: Jun 2011
Posts: 1,041
Likes: 53
From: Sterling CO
neal, Take a look at my signature, notice the: "mostly" stock (<b>T5</b>, 9", radio), "daily" driver. I put 2k miles on the first year after I put the T5 in - "someone who has done the swap before" is the first one here and trying to help.