[Rhinoman]

shep wrote:

Does the vss having a 30% error in reading actual road speed effect how the auto works?

If the VSS is out because of a tyre or R&P change then the auto speed sensor will also be out and your shift points will probably be wrong.

[Gwagensteve]

Is this from personal experience Rhinoman? Because my car runs 3700rpm @ 100km/h (which is, I think, about 500rpm higher than a vitara, at least) and the shift points are spot on. As I have said, my car is throwing a light for VSS so I assume it's either not working, faulty, or the wrong type as it was pulled from an ancient swift.

As far as I know, the TCM doesn't look at the VSS - that's there for emissions. The TCM looks at output shaft speed of the auto with a modifier based on whether the transfer is in low range or not.

Steve.

[JrZook]

Gwagensteve wrote:

Is this from personal experience Rhinoman? Because my car runs 3700rpm @ 100km/h (which is, I think, about 500rpm higher than a vitara, at least) and the shift points are spot on. As I have said, my car is throwing a light for VSS so I assume it's either not working, faulty, or the wrong type as it was pulled from an ancient swift.

As far as I know, the TCM doesn't look at the VSS - that's there for emissions. The TCM looks at output shaft speed of the auto with a modifier based on whether the transfer is in low range or not.

Steve.

TCM requires both VSS and transmission speed sensors. I believe it uses them to determine trans slip and also when to lock the torque convertor.

[Jazzor]

I was wondering how mine knew when to change gears in low range, as there is nothing electrical about the sierra transfer case/hubs etc. The auto monitoring the transmission speed (must be an internal sensor somewhere?) vs the vehicle speed makes sense!

[Gwagensteve]

Jrzook - Interesting. Whilst I am 100% sure your info is accurate, I'd have to say that "required" is too strong a term. My car locks & unlocks the converter flawlessly.

I'm still puzzled about how important the VSS is to the TCM, because of the following: (these are from my personal experience)

Vitaras shift fine and show no errors with transfer gears installed - surely that should provide a huge "error" between auto trans output speed and VSS, even if the TCM acknowledged the car was in low range.
My car shifts fine and shows no errors in low range, and that's with 6.4 gears. I have no low range signal going to the TCM so the TCM has no idea the car is in low range. (I think this is a good thing as I need OD in low range due to my gearing)
If I clear my VSS trouble light, I can drive around all day in low range without it coming back on, with normal auto function. It's only once I've been up to road speed for some time - 15 minutes or so, I get a CE light for the VSS.

Regardless of the CE light on or light off, the car shifts normally, including lockup.


Jazzor: The auto changes gear based on load. It doesn't matter what range the car is in. According the FSM for the AW-4, the low range switch used on the Vitara transfer is there to lock out overdrive, it doesn't do anything else. The auto just changes gear based on the conditions it sees (load, temp, throttle position etc) with little reference to road speed. Thats why it will tend to race through the gears in low range - there's too little load to hold the car in a gear.

[oozuk]

On the subject of ratios, could any body enlighten me on what sort of engine speed i should expect on the hiway @ 100km\hr ?

Also swapping out the sierra 1.3 gearbox for the AW4 could i expect a lower 1st gear ?

My current drivetrain is std 1.3L sierra gearbox, 4,19 transfer gears 4.6 diff gears and 33x13.5 15 tires
currently 100km\hr is approx 4000rpm in 5th gear

[Gwagensteve]

I'm not 100% sure of the 4th gear ratio used in suzuki AW-4's it seems that .73 is most likely.

The sierra 5 speed which is 0.795 (0.865 after 1988.5)

Based on my calculator and your revs at 100km/h, I'd say you have a later manual (0.86 5th) - I get 4001rpm @ 100kmh with an "actual" 32" tyre with your parameters and a .86 5th gear.

An AW-4 would drop that to 3396rpm based on a .75 overdrive, which is very nice.

My car went from 4335rpm @ 100km/h with the 660 5 speed to 3679rpm with the AW-4.

As to the first gear, it's not numerically lower - (3.65:1 for a 1.3 5 speed, 2.8:1 for an AW-4) but below converter stall speed, the converter can gear this down up to 2.4 times, so depending on load, that 2.8:1 could become equivalent to 6.7:1 with a manual. Rest assured, 1st will be plenty low. Once you are above stall, sure the gear is a bit taller, but that's no big deal because by then the motor is making enough torque to cover it. The overall impression is that the gearing is lower due to the effect of the converter.


Steve.

[oozuk]

Gwagensteve wrote:

I'm not 100% sure of the 4th gear ratio used in suzuki AW-4's it seems that .73 is most likely.

The sierra 5 speed which is 0.795 (0.865 after 1988.5)

Based on my calculator and your revs at 100km/h, I'd say you have a later manual (0.86 5th) - I get 4001rpm @ 100kmh with an "actual" 32" tyre with your parameters and a .86 5th gear.

An AW-4 would drop that to 3396rpm based on a .75 overdrive, which is very nice.

My car went from 4335rpm @ 100km/h with the 660 5 speed to 3679rpm with the AW-4.

As to the first gear, it's not numerically lower - (3.65:1 for a 1.3 5 speed, 2.8:1 for an AW-4) but below converter stall speed, the converter can gear this down up to 2.4 times, so depending on load, that 2.8:1 could become equivalent to 6.7:1 with a manual. Rest assured, 1st will be plenty low. Once you are above stall, sure the gear is a bit taller, but that's no big deal because by then the motor is making enough torque to cover it. The overall impression is that the gearing is lower due to the effect of the converter.


Steve.

Thanks steve, that's exactly what i wanted to hear, I've been looking at your build thread and I'm tempted to copy your setup for Vitara full floater rear axle on range rover radius arms coiled, should offer a stronger rear end and not have to worry about axle wrap any more, that's the plan

[shep]

Is it best to keep the Sierra pedals or to swap in the vitara ones? Do the vit pedals bolt in easly?

[christover1]

I've recently disconnected my low range input to the TCM on my Vitara auto.
To enable OD in low range,
needed because of Rockmonster tranny gears being very low.
I'll speak up if any thing bad happens,
but studying various wiring and plumbing diagrams,
I am not expecting anything to go wrong.

[slimmorgan]

Hi Guys I've foolishly started a 4 speed auto conversion into one of my sierras ill prepared. I'm pretty handy with auto electrics so I'm confident I will get the loom sorted. has anyone got any diagrams or any cheating material that might help me along the way?