[djc123]

Hi Guys,

I am about to do a 1.6 16v & auto conversion on my LWB Sierra. It is running Rockhopper series 4 gears (6.5 low range, 1.7 high range) and 5.12 diff gears, rolling on 33" Boggers.

I have a complete running LWB 16 valve 4 speed auto Vitara ready as a donor.

I was talking to the guys at Trail Tough about their automatic conversion kits, and they suggest that the 3 speed auto is a much better option than the 4 speed, as the 4 speed is computer controlled, and the VSS is used to running in front of a 1:1 transfer case - therefore will change gears much earlier when in front of the Sierra transfer case.

Does anyone have much experience with either the 3 or 4 speed auto with a 1.6 in a Sierra? Can the VSS be tricked, or the ECU programmed to shift correctly with the different gearing?

Cheers,
Danny

[Gwagensteve]

That's not my experience. With your gearing, you want the 4 speed auto, or swap back to 3.7/3.9 diff gears. I run your gears and spin 3700rpm @ 100kph with 35's, you'll be about 3900. With a 3 speed you'll be spinning something like 5400 rpm @ 100km/h.

My auto changes fine. In power mode it holds the gears to close to redline.

Steve.

[Fatzook]

X2. 4speed is the way to go.

[djc123]

Thanks guys. I thought that there were a few Sierras around with the 4 speed and no issues. I dont know why Trail Tough seem to think the VSS ouput makes the 4 speed shift too early? They were trying to suggest the auto would be in top gear within the first 30 metres of taking off ...

[Gwagensteve]

They're wrong. The vss signal comes off of the sierra transfer case, and is correct for 26" tyres and 3.7 diffs. If you ran 4.6 diffs with 33's your speedo would read correct and the car would shift normally. If you run 5.12's it will be short geared and shift a little bit more quickly than normal, mostly due to reduced load on the auto.

There may be some differences in setup between US models and here, and there is a speed sensor on the back of the aw-4, but I can promise you they shift fine.

I've driven two aw-4 sierras, one is 100% vitara, the other runs an aw-4 patched to a jimmy computer, and they both shift fine. Both run 35's, 6.4/6.5 gears and 5.12s. I have driven both at highway speeds. There are no issues.

[tanshi]

i think you would find its down to them using the speed sensor on the back of the US model aw4 rather than the cluster speed sensor that we use here.

[djc123]

Good to know. Thanks for all the info guys. I'll move ahead with the AW4 & 1.6 conversion.

[Gwagensteve]

tanshi wrote:

i think you would find its down to them using the speed sensor on the back of the US model aw4 rather than the cluster speed sensor that we use here.

I reckon that's it. However, as sierras don't have a low range light switch, the car would shift crazy in low range. Even if you used the aw-4 mounted vss to get it to shift on road.

Steve.

[JrZook]

Wouldn't be too hard to add a low range switch? Worst case scenario, manually operated.

[Gwagensteve]

No it wouldn't, and IMHO the 4wd switch would do the job because I don't use 4wd high, but in AW-4 vitara 4th is locked out when you are in low range. That's a massive pita with 6:1 transfer gears, in fact I reckon with 5.12s and. 6.4 transfer my car would be undrivable if I couldn't use low 4th.

[tanshi]

as an aside to this i was researching some interesting stuff and found this link. http://www.zukikrawlers.com/showthread.php?t=37680

[djc123]

Gwagensteve wrote:

I run your gears and spin 3700rpm @ 100kph with 35's, you'll be about 3900.

Gwagensteve wrote:

My auto changes fine. In power mode it holds the gears to close to redline.

Steve - do you run your rig in both high & low range without the low range switch on the auto connected to anything?

[christover1]

I disconnected my low range warning light switch, so I could use OD in low range.
I have a 93LWB Vitara with 4:24 rock monster tranny gears.
Was a blessed nuisance without OD in low on my 30's.
No problems with it so far.

[Gwagensteve]

djc123 wrote:

Gwagensteve wrote:

Steve - do you run your rig in both high & low range without the low range switch on the auto connected to anything?

Correct. In high range it makes no difference, but with low transfer and diff gears, in low rangd you really need to be able to use OD.

Steve.

[zooky08]

If i wanted to run a 4 speed on the back of a carby engine what would I need to have. Ecu? Auto harness or hole harness? Dont need a speedo.

[SierraDan]

Manualised.

or the Pajero AW4 apparently.

[zooky08]

Yea I looked into but you still need to source a vitara auto bell housing

[SierraDan]

So?...

[tanshi]

Jrzooks little black box would do it but you would have to hook up a TPS onto the carby motor.

[zooky08]

SierraDan wrote:

So?...

Cant find a 4 speed around here let alone a bell housing

[Fatzook]

PM Rhino. He had a dead one for sale a little while back.

[losfer]

which box would you auto guru's suggest for drag racing . i was sort of leaning towards the 3 speed myself .

[Fatzook]

losfer wrote:

which box would you auto guru's suggest for drag racing . i was sort of leaning towards the 3 speed myself .

You already know the answer to this.

The 3speed is easier to upgrade, probably cheaper too, and if you get your ratios right, you won't need a 4th.

You could always look into a C4....

[christover1]

losfer wrote:

which box would you auto guru's suggest for drag racing . i was sort of leaning towards the 3 speed myself .

2sp Powerglide I think was good

[Gwagensteve]

Hugo's racematics run up to 600hp. Beyond that, a 'glide IMHO. No need for the OD.

Steve.