95 Ford Lightning Info

[T Col]

Hey all - this is not my normal generation of truck to hunt in but I have to expand my research a bit to take care if a problem in my 79.

I am looking for some support in regards to the rear end that was in 95 lightning, previous owner of my 79 took one and put it in and now I am chasing speedometer issues down.

If I have researched correctly, this generation of lightning used only 4.10.1 rear end, later generation of lightning switched to 3.73------ am I correct?????

All help is appreciated on identifying this rear end (I really don't want to have to jack it up and try to rotate and count)

 

[O'Rattlecan]

How is your speedometer hooked up?

In 1995, there was a magnet speedometor sensor mounted on the top-center of the differential. I am curious what the previous owner did to make the mechanical speedometer work. Did he continue to use a sensor on the transmission?

Ryan

 

[5.0Flareside]

Yep your on the money..

 

[5.0Flareside]

How is your speedometer hooked up?

In 1995, there was a magnet speedometor sensor mounted on the top-center of the differential. I am curious what the previous owner did to make the mechanical speedometer work. Did he continue to use a sensor on the transmission?

Ryan

Would've had too

 

[T Col]

Yes the mechanical system is still in place, leaves tranny, goes up to a box on the drivers fender well under the hood (assume it is the cruise control) then out to the instrument panel

It functions but is WAY off, from what I have learned thus far I need to pull / swap the driven gear at the tranny for the proper size and I should be good to go- only part of the math to determine the size of the driven gear was the rear end and while they are cheap I have to order it in and was trying to figure out if this was the only ratio used that year

 

[5.0Flareside]

Yes the mechanical system is still in place, leaves tranny, goes up to a box on the drivers fender well under the hood (assume it is the cruise control) then out to the instrument panel

It functions but is WAY off, from what I have learned thus far I need to pull / swap the driven gear at the tranny for the proper size and I should be good to go- only part of the math to determine the size of the driven gear was the rear end and while they are cheap I have to order it in and was trying to figure out if this was the only ratio used that year

you are once again correct....

to be honest.. i just dont see why the PO did this swap... took alot of work... when couldve just had a gear swap done for the same money and less time..

 

[O'Rattlecan]

It sounds like you have it figured out.

Ryan

 

[T Col]

Yeah,,,,,,, now all I have to do is figure out which of the six gear sizes is the right one. (I guess I am down to 5 guesses since the one that is in there is wrong)

Theory would tell me that I would go with the one with the fewest teeth since the rear end is so low it would be turning fewer times (? - think I am right or backwards with my thought)

 

[O'Rattlecan]

Do you have a GPS or a friend who is a cop that might have a radar gun?

If you can find out your actual speed and then calculate back into it, you can determine the right ratio.

Ryan

 

[Lost]

you are once again correct....

to be honest.. i just dont see why the PO did this swap... took alot of work... when couldve just had a gear swap done for the same money and less time..

I can swap a rear in time you would pull cover. The lightning had a reinforced rear . Not that mattered. Just change u joint and new u bolts everything else easy to do . The 79 had a mechanical any way .

 

[SuperCab]

Im with lost... gear swaps are a pain... swap the whole axle in an hour or two and good to go...

 

[73F100Shortbed]

Yeah it shouldn't have been too much of a pain to do. Sounds like an easier route if you do not know how to properly set up gears.

 

[john112deere]

Wow- I put 50k miles on a pickup with a speedometer/odometer that read ~18% high. Worked out the conversions and learned 'em by heart- never had much trouble knowing how fast I was going. (No fancy technology involved in determining the conversion factor, either- Dad followed behind me in his car while I accelerated from a stop, tooting the horn every 10 mph on his speedometer. I recorded my readings at each honk, and averaged the error together to come up with a conversion.)

At any rate...I'm thinking you want a gear with more teeth, not fewer. The lower (numerically higher) rear-end means your driveshaft/tailshaft is spinning faster at any given speed than a taller (numerically lower) rear end. Since the speedo on that truck is really measuring tailshaft speed, you want to decrease your speedo reading for a given tailshaft speed reading. A larger gear (more teeth) will turn slower than a smaller (fewer teeth) gear, thus slowing down your speedometer reading.


(I'm no expert in this stuff, though- and I've had a few this evening. I could very well be out in left field here.)

 

[T Col]

Well, had one or two myself, and explaining it that way does make sense- so how about my theory in reverse and go for the most teeth available of the speedo driven gears (since I noted most frequently only 6 options for this generation) seeing that the 4.10.1 is just about as low as you would go for that age?

 

[DNFXDLI]

Work out the percentage difference with the gears and tire size and apply that number to the driven gear.

 

[T Col]

I just remembered something from the other thread, revisited it, clicked around and ended up going to:
http://www.transmissioncenter.org/Ford_Speedometer_Gears.htm
Where I noted that they have a 23 tooth gear that is specifically for use with 4.10 rear end

The only veritable that I am not sure of, and honestly, do not want to have to break down the tranny and look (hence why I was trying to figure it out), is whether this is a 7 spline or not

 

[T Col]

But at the same time, found another website that warns against the 23 tooth, especially the white one, as it is supposedly best used with standard transmission and has a history if breakage, possibly should go to the 21 Orange and just figure out the difference

 

[73F100Shortbed]

Do what I do. Don't use a speedometer Mine hasn't worked for more than 5 minutes in 4 years.