4.10 speedo gear

M

Mr. Mark VIII

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I just installed 4.10 gears in my car and I would like to know what Speedo gear to use to correct for the new gears. I have stock diameter wheels. Thanks
 
i dont believe you need to change the speedo gear. its when you change the size of your tire you change the speedo gear.
 
I have a 1998 with 4.30 gears. The speedometer was not affected by the gear change because the speedometer input is from front wheel. Changing front tire diameter does affect the speedometer accuracy as previously stated. I did add a Dallas Mustang Speed-Cal to modify the Vehicle Speed Sensor (VSS) output pulses. I'm not sure what this did for me honestly, but it seemed like the right thing to do.

http://www.dallasmustang.com/page/products.php?category=&group=&family=&product=9910

http://www.blueovalchips.com/index.php?action=speedcal_inst

The earlier cars are a bit different, and can benefit from a speedo gear change from what I understand. A good source is below.

http://www.blueovalchips.com/index.php?action=item&id=25&prevaction=category&previd=4&prevstart=0
 
His mark is a 93. The speedometer is controlled by a sensor on the side of the transmission, not the front wheels. And yes, it will jack up the correct MPH and shifting points. As for the correct gear, I believe it to be a black 28 tooth gear.
 
4.10's will also need a recalibrated PCM, otherwise known as a "tune".

The stock PCM can adapt up to two gear ratio changes without recalibration.

you can go from stock 307's to 355's and not need a tune
or the LSC's can go from 327's to 373's and not need a tune

But if you jump more than 2 ratio's for example 307 to 373's or LSC's 327 to 410's you will need to have a tune from one of the known good vendors that post frequently on this site.

Otherwise your car is going to be shifting into 4th gear at 30MPH which is way WAY too soon.

For simplicity, what is happening is your "shift schedule" and "TC lock up schedule" have become "Compressed", meaning the shift points have been decreased due to the gear change.

I'd suggest Lonnie @ Blue Oval...he writes good solild tunes for our cars or Torrie @ fastpartsnetwork, both of these guys do great work and are very respected in the PCM calibration community.

Hope this helps.


Enjoy those gears!!!!
 
I think it should be a Black 23 tooth gear. Now what I need to find out is how many teeth are on the drive gear 7 or 8?

As for a chip, I was not really sure if i needed one or not. I thought changing out the speedo gear would fix when the car should shift. Right now it will shift into OD when the speedo says 40, but im really going like 30 or so ya everything is early. I thought the gear would just correct for all this.
 
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hey just wondering if gravelguy is right and the speed comes from the front wheel? if so what years are the marks like this?
 
XLRVIII has put out the correct info on this. The 93 - 96 Marks require a speedo gear to correct the change. But if you've gone over 2 steps then you also need to have the changes made in the EEC. So you have to plan on doing both if you go over 2 steps in the gears. Now for the 97/98 Marks, they don't need a speedo gear change since they use the ABS wheel pickup. But they still require a change in the EEC if going over 2 steps.

Now some little known info. The black 23 tooth speedo gear will work with a 4.10 gear ok. You speedo will still be off slightly because you actually need a 24 tooth. Because of the increase is teeth on this gear the teeth have to be made thinner. They don't match up perfectly with the Ford speedo drive gear since these are actually designed for a Jeep. But they have become a standard for anyone with a Ford running 4.10s over the years. They do work but they wear out quickly because of the mismatch and thin teeth. This doesn't hurt anything in the trans by the way. They will just start slipping once the teeth are worn down then your speedo starts jumping around. I tell most people if they are going to go with this speedo gear to get 2 of them since they only last a couple years before you have to replace them. Sometimes longer though. I'm running one of my built transmission and it has an 8 tooth drive speedo gear so I've had to go to the black 23 tooth gear also. So far it has lasted almost 2 years without a problem. I then programmed the EEC to get the speedo to read more accurate.

The other choice is to go with the Speed Cal, I also carry them as does Dallas Mustang who designed this product.

Now going to a 4.30 you don't have a choice for speedo gears since you've passed the correction factor. In the old days Ford supplied a device that you ran the speedo cable through that then reduced the speed of the cable to the speedo. We don't have that with our electronic setup. So your only choice is to go with the Speed Cal and then get a tune to finish the correction.
 
Lonnie said:
Now going to a 4.30 you don't have a choice for speedo gears since you've passed the correction factor. In the old days Ford supplied a device that you ran the speedo cable through that then reduced the speed of the cable to the speedo. We don't have that with our electronic setup. So your only choice is to go with the Speed Cal and then get a tune to finish the correction.
Click to expand...

So what would the outcome of 4.30 gears with a 23 tooth speedo gear be besides the speedo being slightly off? Would it have any impact on the EEC? :rolleyes:
 
driller said:
So what would the outcome of 4.30 gears with a 23 tooth speedo gear be besides the speedo being slightly off? Would it have any impact on the EEC? :rolleyes:
Click to expand...


I could be wrong as I'm only speculating here.

but it would make sense that 4.30's w/23 tooth would be like having a stock mark 8 (307's and going to 373's and not changing the speedo gear).

Atleast it sounds like it makes sense.. before I've had enough coffee to "think straight".


I love reading lonnies posts, no matter what he posts, I always learn "something"!
 
I wish there was a better way to correct the Speedo on gen 1. The 23Tooth doesn't correct the 4.56 enough. It may be time to go taller on the tires if I run out RPM's in the traps.
 
XLRVIII said:
I could be wrong as I'm only speculating here.

but it would make sense that 4.30's w/23 tooth would be like having a stock mark 8 (307's and going to 373's and not changing the speedo gear).

Atleast it sounds like it makes sense.. before I've had enough coffee to "think straight".


I love reading lonnies posts, no matter what he posts, I always learn "something"!
Click to expand...

Not exactly, there's more involved into this than just changing the speedo gear. The trans actually needs to have the correct ratio for the engine speed verses vehicle speed in order to keep the transmission timing correct besides the speedo. With the EEC IV vehicles this is much harder since you can't data log. This then requires experience and calculations.
 
Well I got a 28 tooth gear from my jeep dealer. I’ve read from the mustang guys they would work. It seemed to make the car shift a lot better. It seems to shift into OD at about 35-40 mph. At WOT it will shift at 6k 1st to 2nd to 3rd. I’m really confused why I need a chip. I understand that the shifts happen sooner but isn’t that ideal? Lower gears means less work for higher RPM so I would think shifting sooner (not at WOT) would be perfect
 
Lonnie said:
The trans actually needs to have the correct ratio for the engine speed verses vehicle speed in order to keep the transmission timing correct besides the speedo.
Click to expand...

So, what would be better, a stock speedo gear with a speed-cal unit or the 23 tooth(with 4.30s)?
 
Lonnie said:
The trans actually needs to have the correct ratio for the engine speed verses vehicle speed in order to keep the transmission timing correct besides the speedo.
Click to expand...
]


That is the oh so elusive "N/V" ratio.. huh.
I had a helluva time with that at "first".

The canned SCT tune I got had an NV of 50, stock calibration was 40 for 308's..

I got out on the hiway and checked NV... in third gear, at many different speeds 30mph, 40mph,50,60,70 and a brief look at 100 {haha}

my calculations, with my 373's with 245/50's came out to 50.
(same as 4.10???) WTF?
I guess the shorter tire did that.

Getting the NV nailed down did go along way in getting my car to "act right".
With the stock NV the shift schedules were compressed and the lock up schedule was "really goofy"...
 
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