Putting in a Dana 300

[MoparManiac]

That's weird.

Mine ('92) is still an electronic speedo and all that jazz, but I know for a while it wasn't working and sometimes works intermittently (ran the t-case dry for a couple miles and chewed up the plastic gear that slides on the main shaft to drive the speedo gear).

Never had a problem with driveability.

/hijack

 

[kastein]

90/91 was the changeover, 90 has mechanical while 91 has the electrical VSS. I'm not sure of much of anything else, but I'll poke through my FSM tonight if I remember to. I think the ECU will flip out and throw codes on some years if it sees the OSS indicate too high a speed but the VSS isn't indicating anything, but I don't know which year it started on.

Anyone got info on the stock d300 VSS?

 

[trail rate this]

Tried front dig yet?

No front dig yet.

 

[trail rate this]

I dont have a VSS hooked up. I dont have the right one for my year. It didn't run any different than normal. I just didn't have a reading on the speedometer. The compunter in my overhead console showed my gas mileage was crap.

 

[asp]

i opened mine all the way up. i have some rusty gears. there was a lot more water and crap in it than i thought. not very good. i think i only need 2 or 3 new gears. but i also realized there were no shifter detent parts. ugh. this good deal just got a lot less good.

 

[trail rate this]

Do a 4:1 kit. That will give you new gears

 

[asp]

We can't all just drop the coin on a Klune and 32 spline outputs and a 4:1 kit.

 

[vetteboy]

I dont have a VSS hooked up. I dont have the right one for my year. It didn't run any different than normal. I just didn't have a reading on the speedometer. The compunter in my overhead console showed my gas mileage was crap.

On my '94 anyway, without a VSS signal the engine liked to stumble and occasionally stall out if I suddenly lifted the throttle and coasted after running hard for a while. Apparently it uses the VSS to sense this condition and modulates the IAC some to keep it running.

You can use a stock sending unit from a NP231 and splice the 3 wires from your harness into the old sensor. The basic signal is the same and actually it'll give you the ability to calibrate it by being able to change out speedo gears.

Here's a copy-and-paste from when I was figuring this out the first time with my Stak 32-spline D300 upgrade (which ironically uses your new-style sensor)...

The ECM does use the VSS sensor and throttle position to determine if the vehicle is decelerating. While in deceleration mode, it will use the idle air control motor maintain a set engine vacumn. (Per 1995 FSM, page 14-25). In deceleration mode, the ECM will reduce the injector pulse-width and delivery less fuel (1993-1995 Fuel Injection Manual, page 3).

Now I need to figure out how to use the new VSS on the STaK. From the same FSM, the stock speedometer at 55 MPH is getting a square-wave signal from the VSS at a rate of 122.2 Hz.

The STaK VSS (which is the same as the newer 2003+ TJ VSS) sends 3 pulses per driveshaft revolution. Figuring with my tire size and 4.56 axle ratio, at 55 MPH my driveshaft is spinning at 2250 RPM. So the VSS is sending a signal at 112.4 Hz.

Basically what that boils down to is if I splice the new VSS into the old wiring harness, without changing anything else my speedometer will read ~10% slow. I think that's close enough that I don't need to spend $80+ for a converter box.

In a rare display of helpfulness, STaK provides this package of wiring diagrams for their VSS and all the different Jeep plugs.

http://www.stak4x4.com/pdf/VSS_pinout.pdf

So it's as simple as splicing 3 wires together and I'll have an almost-good speedometer and an engine that doesn't stall/stumble on deceleration. Cool.

 

[asp]

thanks for the good info.

 

[MoparManiac]

Surprised I hadn't felt that before...maybe in my '91 and '92 it didn't do that?

Thanks again for the info Chris.

 

[trail rate this]

That's great info. I haven't had any problems with stalling or stumbling. I do think it's effecting my shift point though.

 

[asp]

i'm getting new D300 gears for the cost of a USPS flat rate box now i just need to put the whole thing back together.

 

[TomMcD]

Surprised I hadn't felt that before...maybe in my '91 and '92 it didn't do that?

Thanks again for the info Chris.

Yours is an OBD 1 XJ, it's possible vetteboy's 94 is OBD II.

 

[asp]

Yours is an OBD 1 XJ, it's possible vetteboy's 94 is OBD II.

OBD II is 96+ (unless he converted it up, but why the hell would anyone do that?)

 

[vetteboy]

Mine is OBD I.

 

[kastein]

Correct. All 96+ were OBD II, some 95s apparently got the OBD II wiring harness as well since many of the sensors (CPS, TPS at least) have two listings for a 95, one for the old connector style the other for the new. 94 was solidly OBD I.

 

[MoparManiac]

I'll look through my '91 FSM if I have time when I get home tonight and see if the VSS plays the same role as Chris's.

 

[trail rate this]

I picked up a 99' VSS at pull a part yesterday. I'll put it in today and see if its all better.

 

[asp]

sweet, good luck. :thumbup:

 

[kastein]

Another question for you - When I do stuff like this (not on vehicles so far, but on other projects) I'm always worried about making sure the shafts line up center to center properly, i.e. the axes are concentric (I'm probably using the wrong terms here.) How did you make sure you were boring the holes through each direction such that the center ended up on the same spot both ways?