Speedometer Correction Gear (1 Viewer)

[powderpig]

In the past if you lost the truespeed and did not have the jumper the truck did not not start. It has to do with the way it was wired into the computer. It may sound fishy, but a couple of customers in the past lost the true speed and called the shop with the "Question As to Why did my truck not start?". I have only installed one and that one ran great. the others were installed by others. It may of been the install, but when you replaced the unit, it ran. If you put the jumper in it ran. I do not remember the wiring the True speed interupts, but in the past it could create a problem.
The problem may also have been fixed in the newer units. I may be wrong Rick, jsut passing on past experence with it. I do not run one from the past experences. good luck with the units. later robbie

 

[tarbe]

All you are doing is running the speed sensor wire through the Tru-Speed (and plumbing power to it, and grounding, of course).

So unless losing your speed sensor would cause the truck to not run (?), the Tru-Speed should not strand you even if it did wonk out.

And reverting back to stock is as simple as clipping two wires and by-passing the Tru-Speed.

 

[landtank]

As Tarbe says, all you do is interupt the Video signal from the speed sensor. Before posting I went out and unplugged my Truespeed and drove around the block. I didn't have any speedometer but the truck ran fine otherwise.

I originally had one of the first Truespeeds available and now have a second one as the first batch had a design flaw and needed to be replaced.

Robbie, do you remember what years those trucks were? Mine is a 96 so maybe there is some different logic used on the older trucks. But I'm thinking it was a funky install.

 

[powderpig]

one was derex's truck(96-97), i can not remember who's the other was. I am glad that you can do what you did Rick. I know it did not make sense to me, but it happened. It may be that the design has been changed to correct this. If you can drive with out it now then something has been corrected. Thanks for using your truck to test out the old problem. later robbie

 

[landtank]

I'm still thinking it's a funky install. If they put their TrueSpeed in at the same plug I did and instead of tapping off the 12v lead they actually spliced into it, then removing the TrueSpeed could cut the power to some of the truck and possibly keep it from running.

If anyone is concerned about this they can simply unplug the speedsensor at the back of the T-Case and see if the truck still runs, if it does then installing the TrueSpeed will have no effect on it's operation if it fails, provided it's installed properly.

 

[Jason Andrews]

If you re-geared to 4.88's that would also set the shift points and the speedometer back to stock specs....but that also costs alot more. lata

 

[tech_dog]

So I'm a bit confused on this. Am I correct on the following?

1) Changing the speedo correction gear helps correct the shift points AND the speedo reading.

2) Using electronic speedometer correction, i.e. truespeed or yellow box, only adjusts the speedometer.

I'm thinking about getting both of these. Am I wasting money on the speedo gear if I use electronic correction, or will I get better shifting if I have both?

 

[Mickldo]

Somebody over here(Mark's Adaptors IIRC) makes a speedo correction unit that has two switch positions. One for DD tyres and one for "play" tyres. Good for swapping between 285 ATs and 38.5" Boggers! Although why you need an accurate speedo with boggers I don't know.

 

[landtank]

Installing either electrical solution by Slee's instructions will correct both Speedometer and shift points. The gear is primarily for running 285s on stock running gear.

 

[p8nt]

I feel like a tard asking this, but I need it spelled out...slowly...in crayon.

I'm going to 285/75/16 Discoverer S/T. I know were only talking about 1.6" of difference, but

Wll the shift points be affected?

If so, will Slee's correction gear correct the shift points?

Anyone familiar with the correction gear install?

Will someone spot me a $20?

Thanks all......

 

[landtank]

the gear will put everything back to stock. With that size tire it's not real noticeable but it is there.

 

[p8nt]

Thanks Rick. Do you know anything about this install? Im not sure where to start.

 

[landtank]

the install is really simple. You unplug the harness and there is a single retaining bolt that gets removed. Once the assembly is out, you remove the gear by pulling a clip off the end and then place the new gear in the assembly. There is an O-ring that is included that seals the assembly to the T-case housing. No more than an hour job.

 

[p8nt]

the install is really simple. You unplug the harness and there is a single retaining bolt that gets removed. Once the assembly is out, you remove the gear by pulling a clip off the end and then place the new gear in the assembly. There is an O-ring that is included that seals the assembly to the T-case housing. No more than an hour job.

As allways, much appreciated.

Clint-

 

[L8Shift]

Once you have the housing assembly removed from the transfer case, you will see how the gear gets removed and goes back together.

I cleaned the area around the housing assembly before removing it from the transfer case; and lubed the new gear before installing it into the housing.
A slim drop light may come in handy as well.

Here's a pic of the parts I removed...

 

[Miescha]

Alright, I'm prepared to be flammed - I did a *quick* search without luck so I'll ask here (and yes, I'm a moron I guess).

My '96 80 shifts slower from first to second with the 285/75 tires than it did with the stock tires - I know it is the tires size change, but why?

To be clear, I also know it is a gearing issue, but I also need it spelled out in big letters and 'with crayons.'

Thanks.

ON EDIT: Never mind - I found it (yes, I'm an idiot and can't search - I'm on the way to shoot myself now).

 

[Sully]

I just put the Mark's adaptor in a couple weeks ago. It's fairly easy because it plugs in-line with the vehicle speed sensor wires (the plug is just above the center diff sensor). You just have to drill a hole in the tranny hump to run the wire loom. Once in, you have to calibrate it with a GPS and flip the appropriate dip switches inside.

 

[CycloSteve]

Has anyone come across a 34 or 35 tooth for the FZJ80 (1996)?

My situation is having 4.88's and 35" tires. The speedo reads 62 when GPS confirms actual speed is 57...it reads 8.7% too high.

This appears to be the opposite problem of most folks. Would love to just replace the gear, and skip the whole electric signal modification route.

 

[thedoctorhunting]

I purchased and installed the 31 tooth gear from Slee on my 5 speed manual 1991 HDJ81.
My cruiser has a speedometer cable and is not run electrically, and my original speedo gear was 33 teeth and not 32.

I was concerned that the 31 tooth would not engage properly on the transfer case drive gear, but it works fine.
I did this while installing aftermarket cruise control. My cruiser has 285's and 16 inch rims , rather than the stock 15 inch rims and prior to doing the speedo gear change my speedometer was out about 7%, and the drive gear change has now made it essentially correct.
The pictures show the original gear, and gear housing, and the speed sensor that I installed for the cruise control

 

[landcrusher80]

Yellow Box

How about the Yellow Box?

UR/Pro Color Correcting Filter

About $100; works great for me.

LandCrusher80