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Speedo


softshellcrab

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New problem/question. Got the new rear end in to compensate for the 32" tires. Need to change out the speedometer gear. I noticed that when I unhooked the cable from the rear of the tranny that I have a VSS plug on it even though I have a 1990. I thought that they didn't use VSS until 1993?????

OK now, I tracked down a gear company and I talked to him and he said I need a 21 tooth gear IF I have a 7 tooth drive cable. I don't see where the drive cable has any teeth on it. I removed it from the housing and it is just a four sided drive cable that connects to the gear that goes into the transmission. So now I am at an impasse. The guy won't call me back so I can order the correct part. They sell gears from 16 to 21, 23 teeth. The information for the gears say that I have to have a 7 tooth drive and I don't know if I do or not.

Help!

Rear end: 4.68, 32" tires. All the calculators on this site does not offer these options. So somebody crush some numbers and give me a gear!

OBTW, I have a 17 gear (green) installed now.
 
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RonD

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VSS was added earlier on some for Cruise, transmission and Rear ABS.

Good read here on the speedo gears: http://www.therangerstation.com/tech_library/Speedogear.shtml
Scroll to bottom for other links

Yes, cable itself just has a 4 sided end, pull out the housing that the cable attaches to, gear is on that.
 

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VSS was added earlier on some for Cruise, transmission and Rear ABS.


Yes, cable itself just has a 4 sided end, pull out the housing that the cable attaches to, gear is on that.
I've read the article. My question is: based on the information in that article, I need a gear that is bigger than the 21 teeth that is shown. The 23 tooth gear is for 4:11 rears and 29 tires, I have a 4:68. Is my speedo discrepancy permanent or is there a place that would offer larger gears? Or, is there a gear that I could change on the back of the actual speedo?

The tech rep at Performance Automotive and Transmission on the internet told me that if I had a 7 tooth cable I would need a 21 tooth gear. Well, I don't have a 7 tooth cable, that is for the older model units without VSS. I'm thinking that all I need to do is change out the gear, so I'm going to order a 21 and a 23, they're not that expensive, less than a 32 pack:icon_bounceblue:
 

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No, no changeable gear on the dash speedometer.

I think he might have meant you have a 7 tooth DRIVE gear in the transfercase/transmission, which you do, it's the gear on the output shaft.

DRIVEN gear is what you are changing

For 32" tire I get 651 rotations per mile
Ratio 4.68
DRIVE gear 7

Formula
651 x 4.68 x 7 = 21326.76
21326.76 / 1000 = 21.32 teeth

So the 21 tooth should be fine

If you had 32.5" tires, 640 rotations per mile it would be
640 x 4.68 x 7 = 20966.4
20966.4 / 1000 = 20.9

So even better for 21 tooth
 

softshellcrab

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No, no changeable gear on the dash speedometer.

I think he might have meant you have a 7 tooth DRIVE gear in the transfercase/transmission, which you do, it's the gear on the output shaft.

DRIVEN gear is what you are changing

For 32" tire I get 651 rotations per mile
Ratio 4.68
DRIVE gear 7

Formula
651 x 4.68 x 7 = 21326.76
21326.76 / 1000 = 21.32 teeth

So the 21 tooth should be fine

If you had 32.5" tires, 640 rotations per mile it would be
640 x 4.68 x 7 = 20966.4
20966.4 / 1000 = 20.9

So even better for 21 tooth
I don't know why I'm not getting answers to my questions, the email link is messed up. Anyway, I asked the same question in another thread before I saw this answer. thanks for your help
 

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No, no changeable gear on the dash speedometer.

I think he might have meant you have a 7 tooth DRIVE gear in the transfercase/transmission, which you do, it's the gear on the output shaft.

DRIVEN gear is what you are changing

For 32" tire I get 651 rotations per mile
Ratio 4.68
DRIVE gear 7

Formula
651 x 4.68 x 7 = 21326.76
21326.76 / 1000 = 21.32 teeth

So the 21 tooth should be fine

If you had 32.5" tires, 640 rotations per mile it would be
640 x 4.68 x 7 = 20966.4
20966.4 / 1000 = 20.9

So even better for 21 tooth

Changed the speedo gear to 21 t. Went on a ride to see how well it works, another problem developed. The tranny starts hunting for 4th gear at 45; it surges, stops, surges again. I shifted to D and it stopped. The MPH works great, but now the surge problem. I guess I'll put the old gear back in until I can find another solution. The only solution would be to reprogram the ECU, but I don't know how.
 

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You shouldn't have to reprogram anything.
The trans rpms are different for the actual speed but shouldn't cause hunting, and you would expect to see any shifting issue right after you changed the gearing(tire size).

I would double check the shift solenoid wires, and the vacuum modulator hose, if '90 has that.
 
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softshellcrab

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You shouldn't have to reprogram anything.
The trans rpms are different for the actual speed but shouldn't cause hunting, and you would expect to see any shifting issue right after you changed the gearing(tire size).

I would double check the shift solenoid wires, and the vacuum modulator hose, if '90 has that.
If I understand you correctly, you WOULD expect some shifting issues with a change in speedo gears? If so, will they go away?

I checked the vacuum hose when I had issues with my engine, and they all are good. I even changed the "tree" just in case there might be one orifice clogged.

As far as the solenoid wires, where will they be?

I should of taken a picture of the speedo gear assembly. It looks as if a previous owner had spliced into one of the wires of the VSS on the assembly. I tried to follow it back into the engine compartment but I lost in in a wire loom they placed it in. I know it is a splice because there is a splice (blue) connector like one you would use to splice into a brake light for a trailer plug. It has been there a while because it had old road dirt and oil on the connector.

I'm reinstalling the original (green) speedo gear, but its actually raining here for the first time since last fall and I can't get under the car:icon_bounceblue: I'm going to a friends garage and I'll let you know what I find out.
 

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Re-installed the original gear, and no shifting issues. The speedo jumps from 60 to 80 and back again; it's still about 15 mph too fast. Unless there is another trick to use, looks as if I'm stuck with the speedo situation.
 

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Wiring diagram for 1990 Ranger shows Orange/yellow stripe wire on VSS with a tap/splice, but doesn't show to where, could just be a ground, but that doesn't make sense.

The dark green/white stripe wire on VSS shows no splice, runs directly to computer.

I can't see any reason for the VSS signal to change with speedo gear change
 

softshellcrab

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Wiring diagram for 1990 Ranger shows Orange/yellow stripe wire on VSS with a tap/splice, but doesn't show to where, could just be a ground, but that doesn't make sense.

The dark green/white stripe wire on VSS shows no splice, runs directly to computer.

I can't see any reason for the VSS signal to change with speedo gear change
Answer me this: will the trans settle down if I reinstall the 21t gear? Or should I leave well enough alone?
 

RonD

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I doubt it's the trans, A4LD has 3-4 shift solenoid controlled by computer, I believe the solenoid prevents it from shifting to OD(4th) unless engine RPMs, speed(VSS) and throttle position are within a specific range, then it activates solenoid to allow OD(4th).
But that could be bass ackwards, lol.

I don't think there is any "learning" by the computer on transmission control.
So "settling down" wouldn't happen.
I would run it with the correct(new) speedo gear, to see if you can pin point the issue.

Does the new gear seem to fit the same?
Do you have cruise control working with old gear, and does it work with new gear, Cruise uses the VSS as well
 

softshellcrab

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I doubt it's the trans, A4LD has 3-4 shift solenoid controlled by computer, I believe the solenoid prevents it from shifting to OD(4th) unless engine RPMs, speed(VSS) and throttle position are within a specific range, then it activates solenoid to allow OD(4th).
But that could be bass ackwards, lol.

I don't think there is any "learning" by the computer on transmission control.
So "settling down" wouldn't happen.
I would run it with the correct(new) speedo gear, to see if you can pin point the issue.

Does the new gear seem to fit the same?
Do you have cruise control working with old gear, and does it work with new gear, Cruise uses the VSS as well
I actually bought two gears: a 21 and a 23. They both fit and work perfectly. You bring up a good point about the CC. When I got the truck from my late FnLaw's family, I noticed that there is an aftermarket cruise control on the turn signal/wiper pod handle. It is attached with a hose clamp, which is kind of cheap. Now that you said the CC gets it information from the VSS, the wire splice on the VSS, I bet, is the signal for that after-market CC. I did not try the CC with the new gear(s), but it sort a works with the old one. The speed with the CC will drop when going up a hill because, I think, the tranny is not shifting to 3rd gear, in other words it is not responding to decreased speed/rpm's.

With the near tranny gears, I noticed the RPM's are considerably higher than with the old one, but the shifting is far better with the older gear and it runs at 2200 in OD at about (and this is a big guess) 60-65 mph. When the trans gears down for ascending a hill, 3rd gear cuts in and it will be 3000-3200 at 60-65. If I remember what the installer told me the tach would be about 3000 at 65 in 3rd gear based upon the new rear end, so those numbers are correct. Which raises another question: where does the tach get its information: electronic or from the speedo?

To be sure, I'm a little fuzzy on the relationships of speed/rpm's and shifting patterns of this transmission. I really don't notice any relationship change from my old OEM setup and the new setup with the new rear end as far as the tach is concerned. I'm still seeing shift points at basically the same RPMs, except when the truck wasn't running right prior to fixing the timing problem when it hardly shifted from OD. With the exception of the speedo issue, I would rather have a perfectly shifting tranny than a correct speedo and crappy response that could hurt my tranny.

Thanks for your help in this issue.
 

RonD

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In a 1990 4.0l the tach signal comes from the EDIS module, which gets it from the crank position(CKP) sensor.
2.9l would be from the coil

Lets do a little math and see what comes out
Stock tire size for 4x4 would be 28", common rear ratio was 3.73
A4LD has 3rd gear of 1.00 and OD(4th) as .75
2,000rpms in 3rd will be 45MPH
3,000rpms 67MPH

2,000rpms in 4th(OD) 59MPH
3,000rpms 89MPH

32" tires with 4.68 differential
2,000rpms in 3rd 41MPH
3,000rpms 61MPH

2,000rpms in 4th would be 54MPH
3,000rpms 81MPH


Not seeing a large difference, so don't know why trans/computer is having an issue.

Yes, that spliced wire is for the add-on CC
 
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softshellcrab

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In a 1990 4.0l the tach signal comes from the EDIS module, which gets it from the crank position(CKP) sensor.
2.9l would be from the coil

Lets do a little math and see what comes out
Stock tire size for 4x4 would be 28", common rear ratio was 3.73
A4LD has 3rd gear of 1.00 and OD(4th) as .75
2,000rpms in 3rd will be 45MPH
3,000rpms 67MPH

2,000rpms in 4th(OD) 59MPH
3,000rpms 89MPH

32" tires with 4.68 differential
2,000rpms in 3rd 41MPH
3,000rpms 61MPH

2,000rpms in 4th would be 54MPH
3,000rpms 81MPH


Not seeing a large difference, so don't know why trans/computer is having an issue.

Yes, that spliced wire is for the add-on CC
Hmmm, don' think little Nellie is going 81mph in third! Of course, I don't know how fast I'm going no matter what the speedo/tach says!

Now I'm beginning to question the accuracy of the speedo at any speed or rear end configuration. Maybe I've got a dash speedo gear issue since it bounces around so much. Changing out the speedo cable maybe? Maybe it's sticking?

Still doesn't answer the question of why I'm having shifting problems with the change in speedo gears. The coil output certainly wouldn't be affected by a speedo gear issue. Do you think the aftermarket CC might be crossing wires somewhere? Vacuum?

If I could track down the wire and disconnect the fuse to the CC and see if it has any effect.
 

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