ok..im full of questions about my truck and i seem to have found a good place to get em answered finally(unlike my other forum were there all GM sport compact tuners lol)..anyway,i was talkin to my friend the other day and we were talkin bout have'n a 4wd SUV in snow vs a 2wd like my old cavalier Z24 in snow and he asked me about the 4wd in my truck and i honestly had no idea on the details of it,ik its called Smarttrak(i think) but i don't have the option to choose 2wd or 4wd like ive seen in some blazers w/ the push button so some one plz tell me how the hell the 4wd works in my olds bravada?? thanx cuz i have no

 

The 97 Bravada Smart Trak has the older AWD system, 65% of the torque goes to the back wheels, 35% to the front. When wheel slip is detected, it can give more torque to the front as well, but no matter what, it's always powering both axles.

In 98, they went to a full time rear wheel drive system that only engaged when slip was detected. Someone correct me if I'm wrong, but isn't this the same feature as the auto 4x4 that came in the SLT Blazers and Jimmys?

 

I have a (really nice, CLEAN, LOW MILES) Bravada... but the "SmartTrak" system is B.S. man! I didn't know that it IS "THE EXACT SAME" THING AS THE "AUTO-TRAK" or whatever the Blazer/Jimmy trucks had since 1999 (as an OPTION). What sucks is... Although I LOVE my truck during the winters months...it's a major pain in the A$$ during the summer. Gas Mileage suffers a little bit, tires are must be PERFECT on air psi and all tires must be the same size/model... it's just DUMB. I do love it, for being so great in the snow, but why in the hell would Oldsmobile decided to make it STANDARD, and "FULL-TIME" in the "Auto 4wd" feature that the other trucks got?

I def should've bought the (SUPER RARE) and siiccckkk BLACK '00 (last year made!) Jimmy "ENVOY" that I found a couple weeks after buying the Bravada. Ehh, oh well.

Here are the details on our Bravada's "SmartTrak" <--not THAT "Smart" to me though. lol

'98-'01 Bravada's "Smart Trak" system featured the computer controlled NP-136 transfer case, which works more like a traction control. The Bravada was now run RWD in normal operations and only when wheel slip is detected does the "SmartTrak" kick into AWD. (The Front Differential is always engauged)

(it's totally different...and much improved, over the '91-97 Bravada's SmartTrak system also) I believe the '91-'97 SmartTrak set-up was IDENTICAL (or VERY SIMILAR) to the AWD System on the ('91) Syclone and ('92-'93) Typhoon trucks.

 

AirRideFanatic,
If you are having problems with the NV136 transfer case, you likely have an issue with the fluid condition. If left in a degraded state long enough, it can burn out the clutch packs which can cause some very annoying drive-ability concerns.

The NV136 transfer case in my old '00 Bravada (used in all 98+ s-series Bravada's) worked flawlessly year round in NY. And the same setup in my '04 Rainier works great as well.

The '1' in the NV136 nomenclature means that it is a single speed transfer case; differing from the NV236 transfer case which has a low range. Other than that, there are many similarities between the two. The NV136, like the NV236, has a viscous clutch in the transfer case that can bias torque from 0/100 Front/Rear all the way to a locked 50/50 F/R. You can definitely say that the Smarttrak arrangement is like driving an NV236 equiped truck around in Auto4wd all the time. About the only downside of this system, IMO, is that you cannot command it to be locked in.

It is true that the front axle is engaged all of the time which, IMHO, is a welcomed reprieve from the complicated and often problematic front axle engagement system that is used on all of the rest of the 4wd s-series trucks. While the constant turning of the front drivetrain does add a bit of parasitic loss to the vehicle, my old Bravada still maintain ~20MPG highway loaded down with +300# of tools most of the time. This dropped to ~16MPG combined with ~70% city/rural driving. So I wouldn't put a lot of concern into it if that was weighing on your mind.

Like the NV236, the NV136 requires GM AutoTrak II fluid. While it is about two to three times the cost of regular ATF, it's properties are essential to the health of the viscous clutch. And with a service requiring just shy of 2qts, it isn't something you should try to cut corners on to save a few dollars.

 

I've never had issues with SmartTrak, either(parents have a Bravada)
Funny thing is, my Blazer gets worse mileage, 16 vs 17. Then again, I do drive less "conservatively" than my mom, though...

It's a good system. Aids in traction, helps with handling, and does surprisingly well offroad. Even without a low range.

I thought that SmartTrak ran at a 35/65 split most of the time, though.

 

The Borg Warner units used in the pre-98 AWD applications (Bravada, select Blazers, Typhoon, Syclone, & the vans) was a dedicated torque split. The newer ones are adaptive. I can't remember if they used the same marketing name for the earlier Bravadas...

 

Ah, that makes sense then.

If you mean the SmatTrak name, than yeah, it's always had the SmartTrak name.

 

swartlkk- Wow! Thank you for such a great explanation. Ohh okay- I see... the '99-'01 Jimmy/Blazer's with the OPTIONAL 'Auto 4wd' feature was the NV236 transfer case, then? Well.. one thing- that does make sense, it that the "on/off" capability of the NV236 does seem like reason for it to have it's OWN issues. (like NOT engaging the front axles at all b/c of parts wearing out or breaking...vs. the Bravada's front axle, which is always "Engaged", right?) I don't know... my main concern is that it's not operating AT LIKE it should... and I read all about the GM bullentins on correcting the crows hop, etc. So- I just drained and flushed (as good as I could, with the little, hand-held little pump that I bought to be able to FILL it back up) the transfer case about a month ago... maybe 400 or 500 miles ago. Still acts the same. It's GREAT, just really BITES, and HARD on tight corners (example would be--> going through a Drive-Thur window) and ESPECIALLY when backing up. It's like the Clutch-Pack isn't FULLY "releasing" when backing up. (I used the word "fully" b/c I'm assuming it's 'binding' in the first place due to a slight MPH difference in the front & back wheels- and APPARENTLY... the SmartTrak is 'THAT' sensitive.

Only thing I can think of that may help- is adding 2 more psi to the front tires than the I'm running in the back, or maybe let 2 psi OUT of the rear tires (and run 30, instead of 32)..??

OR... flush the transfer case AGAIN... ?


GUYS- Three days ago I pulled the 'ATC' fuse (10a, I believe) under the hood... and it STILL seemed to be grabbing and biting around corners... so I, THEN pulled the '4wd' fuse (20a) on the INTERIOR fuse panel (left-side of the dash) also.

I have NO IDEA if that's a SAFE or 'ACCEPTABLE' way of disengaging the AWD, temporarily (for the summer months) or not. I just want to have a 2wd Bravada, during the summer, b/c of the tire psi and MORE IMPORTANTLY tire SIZE issue that I'm having

(I have a beautiful set of 20" Alba wheels with 255/35's on two and 245/35's on the other two- since I had them on my 2000 Grand Prix "GTX" (GTP with Ram Air, by SLP!... it was such a fun & RARE car ... anyway- can I throw the 20's on the Bravada with these fuses pulled... or should I IMMEDIATELY put them back in... and stop being an idiot about the AWD? haha

THANK YOU SOOOO MUCH FOR ALL OF THE HELP. By far, the best forum I've been on in the past decade. No doubt about that! I really appreciate the help.

PS- I seriously feel like the AWD is STILL "ACTIVE", even though the fuses have been pulled... !! (I'm assuming that I HAVE to be wrong- but as soon as I find a nice gravel parking lot tonight, I'm going to turn the wheels, and carefully see if the front wheels spin when I 'step on it') ha

 

DO NOT put the different sized tires on the bravada that will burn up the transfer case

 

I dont know how safe that is, but you could always remove the front driveshaft like a tow truck guy would have to do to tow you. The Sy-Ty guts take off the front shaft for dyno jobs, so I imagine you could to it too. That would definatly disengage your front wheels. I would wonder if your tires are worn differently on the front and back making you feel that tugging in turns...? I know the tires have to have the exact same wear on them or else they will murder your gears and tcase.