Howdy y'all,
I just bought myself a 1993 f250 non-turbo idi diesel 4x4 w/ 5 speed stick. When I bought it the man who owned it said the speedo didn't work as the rear end was changed from the original limited slip to a 1988 posi-trac rear end. He said the original speed sensor was on the rear end an' I needed to buy an adapter to make the speed sensor work with this rear end. Well, I took his word for it, but I'm not sure he knew what he was talkin' about as I could find no place for a speed sensor to fit. I really don't want to change the rear end to a newer one as I'm short on cash from buyin' the truck. Is there any place else I can hook the speed sensor or a different type of sensor I can buy to go on the tranny or someplace else easily without any major work? I'd appreciate any advice on this matter.

Thanks,

Hondo

 

No help from anyone? I'm suprised.

Well, I'm pretty sure I can't hook up any type of sensor to the rear end to get my speed, but did the 5 speed tanny retain the port and gears that drove the pre '92 trucks speedo's? if so can I hook up to that with the correct sensor? I saw a sensor on an auto parts website listed for '93 that said was labeled as Vehicle speed sensor for transmission. Is that what I need? and i so where is the port on the tranny located?

 

you can check your Tcase for a hole and install that style sensor (unlikely). Pre 93 speed sensor trucks had them in the tcase. or mod the current diff for the speed sensor, or find a post 93 diff which already is equipped, AND is the better diff anyway. can usually find sterlings pretty reasonable price, then sell yours to offset the cost.

 

The '88 diff should have an RABS/VSS sensor in it too, have you looked?

 

Yup, I looked. The '88 diff. has no wiring ran to it anywhere nor do I find a port for any.

How would I modify the tcase or difff. on this truck for the VSS? I've never done it before an' I'm not finding any kits or helps online for that so far.

 

That not sound like 88 rear axle it must be before 87.

I swap rear axle from 91 F250 but rear axle must come from 88-90 diesel.

It work fine. It have speed sensor top of pumpkin.

 

If the donor axle really came from a 1988 truck it will have a VSS on it. If it doesn't... well then he lied to you.

You're either going to have to use an axle with a VSS in it or figure out a way to use a sensor to get the required signal from some moving part of the drivetrain. I saw a setup where a guy made a tone ring with the teeth spaced out the way he needed them and mounted it on the driveshaft. You would have to do some calculations to figure out how many teeth it would need and then do a little fab work to mount it.

 

Agreed, you're looking at another axle swap unless your trans or transfer case has a VSS port on it.. which isn't likely if it's all original.

I'm not sure why anybody would swap an LS diff for a "posi" unless it was to accomplish a gearing change.. because there is no such thing as a factory Ford "posi" they are all limited slips, so nothing was gained by doing this. It's pretty obvious this guy got his info wrong on the axle so it likely he didn't know that Posi and Limited slip are just different names for the exact same thing.

 

Oh I didn't even see that. Posi-traction is a GM marketing term for a limited slip. If it was to do a gear change then I'd be worried that he didn't swap the front to match.

 

Always assuming the best of folks, it's possible he did grab an axle out of an '88, but somone had previously swapped that truck's axle with an earlier one.

 

I didn't know they were the same either. I had a Bronco with Posi-trac an' thats what everyone referred to it as. The reason he said he changed the rear end out was that the owner before him pulled other folks out with the truck, while muddin' or the like, and he messed up the rear end bad on it. What went bad, axel, gears, bearin', I don't know. He got the rear end from his Father-in-law who is a diesel mechanic. Now y'all are sayin' that the 88 would have had a sensor on the rear end. I've posted this question on several forums an' I've had a few folks say that prior to '92 they were all on the tranny or transfer case, an' from '92 on up they were all on the rear end. I know on the auto tranny's they had speed sensors for shifting, but on the 5 speeds I am not sure. One guy told me I might be able to swap the small rear housing off of my tranny for one from the 80's an' I'd be able to hook a sensor up there. I appreciate all the help, believe you me, but honestly I'm a might confused on what is what, as far as what years had the speed sensors where. Does no one make some after-market add on speed sensor to go on the drive shaft? also, on the rear end where exactly did the sensors go?

 

Everyone was wrong. It's a very common mistake though.

They're all wrong too. All F-series rear axles from 1987 & up have a vehicle speed sensor mounted on top of the differential. It was used for RABS in 1987 to 1991 and for the RABS and speedometer from 1992 to 1996. Trucks from 1987 to 1991 also have a VSS on the cable output on either the transmission or the transfer case but that VSS was not used for the speedometer, but the PCM used it to control shift points. 1992 and newer trucks only use the one VSS on the rear axle.

You are really getting some bad information. Since your truck is a 4x4 the speed sensor is in the transfer case not in the transmission. Regardless it won't give you the correct output to run your speedometer.

No one makes an aftermarket kit that I know of. There isn't a lot of demand for it because the factory axles with VSS mounts and tone rings are just SO common in junkyards. The sensor sits right on top of the pumpkin and reads the speed signal from the tone ring bolted to the carrier.

 

Thanks for the info. I'll let y'all know what I come up with. I might ask some follow up questions later. I can't get to the junk yard until Saturday as they are closed by the time I leave work.

 

Well, I found a solution. My rear end must be older than '88 as there is no place to put a speed sensor on it. I looked at my Dad's '97 ford f-250 the other day for reference an' on mine there is nothin' in that spot. I don't want to mess with tryin' to use the transfer case to get a speed right now an' I don't have time to change a rear end an' they aren't cheap, 'specially If I get a reworked one. If I go to a junk yard I'd hafta rebuild one as I'd not be sure of the condition it was in nor if the gear ratio was right. SO I Am getting this: GPS Speedometers Gauge, Revolution Gauges Series by SpeedHut Give a big ol' Howdy to the GPS powered Speedometer. I know it's not cheap an' maybe for a little more I could have a rear end, but I'm runnin' 35" tires on my truck so I'd hafta git me one of those speedo calibrators to get anywhere clse to the right speed showin' so I'd be out another $250 to $300. What y'all think?

 

No, your '93 uses a PSOM to drive the speedo/odo. It's free to reset for different size tires.

Courtesy Steve83: What's a PSOM & how do I "P" it???