Bigreen505's Trooper Mod tread

[bigreen505]

We got enough snow out of the this storm to make the roads very slick. Tonight I set up a test loop to figure out if my crappy tires are making the truck almost unsafe to drive in snow or if it is the TOD system. Okay, it wasn't a test loop, it was an out and back trip to the grocery store. Speeds were low so I went there in TOD 4-hi and back in 4-lo. Going there was the typical, borderline in control experience that I had previously driving the Trooper in snow. Coming back in 4-lo (center diff locked) was rock solid with completely predictable handling compared with random freak oversteer in TOD 4-hi.

The little test confirmed that the TOD mod (either power or cut wire) is necessary in slippery conditions where 4-lo is not appropriate. And while my tires are worn below what I consider a safe level (about 6/32 on the front, 8/32 on the rear), they are not the problem.

The TOD setting is nice to have, but because of the way it works, I can't imagine it is that much better than simple RWD except while accelerating because it engages minimally and very late.

 

[Scott Brady]

I know TOD is engaged electronically. I wonder if there are any mods out there to either manually engage or change the responsiveness.

 

[bigreen505]

The TOD power mod puts a dummy load in the circuit telling the computer that there is a speed differential between the front and rear wheels (i.e. slip) so as soon as power is applied it locks the differential. This gives you 2WD, unlocked 4-hi, locked 4-hi and locked 4-lo. From what I understand it costs between $50-$75 in parts depending on whether you use an Isuzu 4WD switch or not, and about an afternoon to install if you are pretty good with automotive wiring, which I am not. It is just a matter of doing it, but I can always find a better way to spend my time.

I don't know of any way to change the responsiveness of the system.

 

[Scott Brady]

Try running your front tires at 42 psi and your rear at 28 psi and run the same route... A little Scotty trick that I will take credit for if it works

 

[bigreen505]

I'll try it in the morning and report back.

 

[bootzilla]

I need to do this mod, too. I have the switch mentioned in the article on PlanetIsuzoo - part number # 2-90071-807-0 ... it was only $8, but the thing is, that switch is flat, so it is going to look a little out of place in the dash next to the rounded switches....a rounded switch like the factory one would look better.

I might give it a try this weekend, if I get a chance to pick up a relay and the other parts...

 

[bigreen505]

I'm reporting back. Scott, the change in tire pressure did not succeed in tricking the system into thinking there was slip, if anything it may have had the opposite effect slightly. However it did temper the snap oversteer slightly. It is still there, but not random, not as sudden and much easier to regain control.

Bootzilla, I'm not sure what to do about the switch. I like everything to have a nice factory look to it, but unless you go full out on the wiring (which is a possibility, just not one I had considered) it may be bad to engage the transfer case (4WD) without first locking the drive flange (4WD auto). In otherwords, you have to engage 4wd auto and then 4wd or you may risk damaging something and I'm not sure having two switches side by side that look and feel nearly identical, but have to be turned on in order, is a great idea.

The $8 switch looks like an $8 switch, but you are unlikely to hit it first by mistake and it is recessed slightly giving some protection from accidental engagement. Clearly the best way to go is the full wiring job (the one that will automatically lock the flanges before disengaging the TOD clutch) with the Isuzu switch.

I also got to play with the difference between TOD 4-hi and 2WD and the TOD is definitely an improvement, primarily affecting directional stability, but a very long way from a locked center differential. In any sort of a turn it is pretty useless since it is only sending power to the front wheels if it detects them spinning. Bottom line is you have 4wd when you don't really need it, but 2wd when you absolutely must have 4wd. Still it strikes me as being useful to have enough to go to some degree of difficulty to wire in an alternative rather than the 30 seconds to cut the wire and disable the TOD system.

 

[Scott Brady]

I'm reporting back. Scott, the change in tire pressure did not succeed in tricking the system into thinking there was slip, if anything it may have had the opposite effect slightly. However it did temper the snap oversteer slightly. It is still there, but not random, not as sudden and much easier to regain control.

As always Bill, you are one smart and perceptive dude...

1. I did hope that the system would be quicker to respond with the change in diameters (assuming there is a tolerance before engagement, the dia. change should improve responsiveness). Any more adjustment would have a negative effect on #2. Based on your comment about "not as sudden" it is likely that the system is engaging a little sooner (before the F/R wheelspin variance is too great).

2. Increasing the pressure in the front tires promotes understeer, reducing the pressure in the rear reduces oversteer, which combined should make the Trooper more predictable and neutral.

While not completely safe for everyday (or high speed) situations, it would be interesting to see what would happen if the rear was set to 24 and the front to 45.

Another point I forgot to mention is the G80 LSD, which is VERY tight. That is another contributor to the ill-behaving rear end.

Bootzilla, I'm not sure what to do about the switch. I like everything to have a nice factory look to it, but unless you go full out on the wiring (which is a possibility, just not one I had considered) it may be bad to engage the transfer case (4WD) without first locking the drive flange (4WD auto). In otherwords, you have to engage 4wd auto and then 4wd or you may risk damaging something and I'm not sure having two switches side by side that look and feel nearly identical, but have to be turned on in order, is a great idea.

What about putting the factory switch to the left of the steering wheel? I have two knock-out positions.

I dont think there would be any problem with engaging the CDL before the drive flange. GM 4wd technology uses heat to expand a fluid and it is very slow to engage. You can be driving for a few miles before the flange locks in.

It would actually have some interesting advantages, like 2wd low.

I also got to play with the difference between TOD 4-hi and 2WD and the TOD is definitely an improvement, primarily affecting directional stability, but a very long way from a locked center differential. In any sort of a turn it is pretty useless since it is only sending power to the front wheels if it detects them spinning. Bottom line is you have 4wd when you don't really need it, but 2wd when you absolutely must have 4wd. Still it strikes me as being useful to have enough to go to some degree of difficulty to wire in an alternative rather than the 30 seconds to cut the wire and disable the TOD system.

It seems that the TOD uses a clutch system that is engaged with electrical current. It would be interesting to connect a volt meter to the power wire and monitor the voltage and if it varied (or was just on or off). Knowing that would allow for adjustments to the input voltage, a la Subaru WRX STI

 

[Scott Brady]

I am sure you have seen this, but just incase others have not:

http://www.planetisuzoo.com/articles.htm?id=109&4-HI_conversion_for_TOD_equipped_Isuzus

 

[bigreen505]

It seems that the TOD uses a clutch system that is engaged with electrical current. It would be interesting to connect a volt meter to the power wire and monitor the voltage and if it varied (or was just on or off). Knowing that would allow for adjustments to the input voltage, a la Subaru WRX STI

Scott, thanks for all the comments. I will consider separating the controls.

My understanding is that power is sent to the front wheels in thirds, maxing out at 50/50. As soon as you engage TOD there is a 10/90 split, and the lights on the dash suggest the split is variable.

 

[Scott Brady]

Scott, thanks for all the comments. I will consider separating the controls.

My understanding is that power is sent to the front wheels in thirds, maxing out at 50/50. As soon as you engage TOD there is a 10/90 split, and the lights on the dash suggest the split is variable.

Very interesting. I would sure think that a variable voltage input would allow you to adjust the responsiveness of the system. It might be interesting to mess with and could be a cool mod :smiley_drive:

 

[bootzilla]

TOD has four modes - a front/rear split of 0/100, 15/85, 30/70 and 50/50

The control unit monitors front and rear speed sensors that, according to the manual, output between 0.7 to 6V.

I am curious how the WRX guys tweak this - boost the output voltage somehow to get the diff to act earlier?

Hopefully it won't rain tomorrow, I might take a crack at it...

 

[ZooJunkie]

TOD has four modes - a front/rear split of 0/100, 15/85, 30/70 and 50/50

The control unit monitors front and rear speed sensors that, according to the manual, output between 0.7 to 6V.

I am curious how the WRX guys tweak this - boost the output voltage somehow to get the diff to act earlier?

Hopefully it won't rain tomorrow, I might take a crack at it...

most of the Subaru WRX guys don't tweak the AWD system. That system is mostly a 50/50 split and does not vary, so it's an entirely different system than the TOD. The Honda does 0/100, 40/60, 30/70, and 50/50 splits, and acts more like the TOD on the Trooper. Both the WRX/STi and Mitsubishi EVO 8/9 are all 50/50 split awd systems.

 

[Zaphod]

Another rear cargo rack project:

http://myweb.cableone.net/bcanderson/trooper/Storage/storage.html

 

[bigreen505]

I purchased a set of Bosch Icon wiper blades early this spring to replace my worn out wipers.

...

Summary:
The Bosch Icon is a clever design, but not a totally functional one. At $45 a set ($22 each) they are too expensive for a summer blade and not good enough in snow to qualify as a winter or all season blade. If you feel compelled to spend that much money on wipers try the Silblade, Pangaea carries them.

Overall I am not impressed and want my money back.

I may need to temper my comments. The one problem I had with them in snow seems to be an isolated event, but one worth consideration if you live in an area that sees wet snow. So far they have been fine with that one exception. I will report back when they wear out.

On a side note, I'm still scratching my head about cargo storage. A recent trip that saw six pairs of skis, snow shoes, camera gear, porta-crib, baby sled, stroller and a week worth of clothes, ski gear, laptops and work related stuff, food and assorted other odds and ends (no dogs on this trip, no room for them either) again had me wishing for some sort of cargo/gear organization, but also wondering what something flexible enough would look like.