[mantooth]

Hey everyone!

I’ve got a 96 bronco with 351w that years ago I swapped in a 9” and a np435. I haven’t had a Speedo since then which has been a hassle. Been spending lots of money and time fixing all my mistakes and neglect from being a broke college student. Long story short I’m trying to get the speedo working again.

My question being has anyone managed to make a speed sensor in the tail housing of a bw1356 work with a 92-96 style cluster? Pictured below. Otherwise I’ll make my own version of the desolate kit also pictured below.

This thread mentions trying to use it for an aftermarket speedometer but haven’t seen anything about using it for the stock one. I have this style transfer case in my bronco currently and would like to use the stock sensor.

Electronic speedometer

I have a BW1356 with the speedo gear in the tail housing. I've been searching for an aftermarket electronic speedometer sending unit for the tail housing, no luck! Any out there? I'm replacing the guage cluster with aftermarket. Any suggestions are mucho appropriated!

www.fullsizebronco.com

 

[mantooth]

First picture is of a mechanical speedometer… pre 1992, the other is for electronic speedometer 1992 and later. Since yours is a 1995, you have an electronic speedometer, inorder to go to a mechanical speedometer you would need to A) get an aftermarket speedometer, or B) swap in a pre 1992 Dash and instrument panel.
The best option is the Desolate Kit you showed in the second picture.

The first picture is both mechanical and electrical. It has a plug on it and has some sort of electric pulse output. Looking for someone who has taken that pulse and used it for the stock dash.

 

[mantooth]

The VSS output on photo 1 is sent to the PCM, E4OD transmission control, and Speed Control. It's output is the standard 8000 pulses per mile. You could tap into that VSS signal then send it to the PSOM input of your current instrument cluster. Set the calibration constant to 1, maybe zero?, so the PSOM will not try to divide the signal down. Or if you find the Speedometer/odometer is not accurate because of larger tires, gear change, etc. figure out a new calibration constant to correct it instead of changing the drive/driven gears.

So in theory I just need to hook it up to the original vss connector from the 8.8 and do some basic math to convert because of my 36” tires, 4.88 gears, and the change in pulses. Shouldn’t be too difficult. Thanks!

 

[mantooth]

I suggested going straight to the PSOM since the 4WABS module is prone to blocking the VSS signal. In theory you could even bypass the PSOM as well, but having it in place makes it a bit easier to wire in and having the functionality of using it to correct the transfer case VSS pulses per mile. Just be aware the math to figure out the new calibration constant will be very different than the regular formula since the axle mounted VSS uses more pulses per mile because of the tone ring tooth count.

Well that's a good suggestion being that I also deleted the 4wabs pump when I did the SAS. Yeah I get that too but still shouldnt be too difficult. Equation should be something like "new calibration" = "stock calibration" x (stock 8.8 pulses / stock bw1356 pulses) x (stock tire size circumference / new tire size circumference) x (1 / gear ratio). If anyone has any corrections let me know.

 

[mantooth]

first problem is that the 92+ BW1356 do not have that gear driven VSS in the back. which is why you dont see one on that second picture

second problem is that 'pulse per mile' is pretty far off. the 92-96 is 8000 pulses per mile. the 91 and older i am unsure but it is i think around 1000 IIRC. might be less

an 8.8" uses a 108 tooth tone ring on the ring gear. so every 1 rotation of the tires is 108 pulses. regardless of gear ratio

the sensor on the tcase is 6 pulses (i think) per rotation. its on a 16-21 tooth gear which is driven by a 7-tooth drive gear, that means the sensor pulses 2.2-3.3 times per driveshaft revolution. multiply that by gear ratio (using 3.55 as example), thats pulses 7.8-11.7 times per wheel revolution. more with higher ratio

the PSOM gives some flexibility but not nearly enough for that

your best bet is a GPS speedometer. or somehow adapting a front wheel ABS sensor to work which may be possible but i never heard of it being done. an issue is while turning it will be off but i dont think you care that much being for just the speedometer

this pic looks like its on a 54 tooth ring so half of the rears 108 tooth. you MAY be able to adjust the PSOM to handle that

View attachment 197871

I do have a bw1356 out of a 91 so I'm good there.

Is them being pretty far off an issue as long as you calculate the new psom value correctly?

Ah I wasn't aware there was a minimum for PSOM values as I've never adjusted one.

I have a SAS D44 so no ABS sensors up front. Is there a method for connecting a GPS sensor to work with the stock dash speedo?

The more you explain it seems like the easiest method is making my own setup similar to the desolate kit with the right number of pulses to compensate for tire size and gears to get me close and recalculate based on a phone GPS speed if it seems off. I've got a CNC Mill at work and Solidworks so I will just finish drawing my version of it.

 

[mantooth]

I am not aware the 1991 and earlier PCMs and Speed Control used a different VSS signal standard than the 1992 and later. Both should be designed to use a 8000 pulses per mile signal. The PSOM divides down the rear axle mounted VSS signal so the computer (E4OD only), speedometer and Speed Control system will function.

If it turns out the VSS signal standard is different for 1991 and earlier I stand corrected.

I agree the 1992 and later transfer cases do not have the drive/driven gears to run the VSS signal generator in the OP's first photo.

If you think they should both be on the same number of pulses I'm going to just connect the factory speed sensor connector to the bw1356 sensor and jack up the rear end and see if any speed shows up on the speedo and go from there. Easy to adjust later on if it does show any amount of speed.