Selec-Trac full time 4x4 4WD system discussions

[Thau]

Curious what users of a modern Selec-Trac experience as far as fuel economy compared to a standard selectable system

My KJ was an early model with the 3.7L with the 4 speed out of the Dodge Ram (two 2nd gear ratios). In 2003? They switched transmissions to a more efficient unit. The joys of early adapters!

I saw around a 1MPG drop when left in Full Time (AWD) mode versus regular 2WD. Which is why I just left it in 4Full for so long.

Sponsored

 

[RobNY]

Any chance the JL Wrangler Selec Trac ends up being like the Ram 1500's "on-demand" full time 4WD. That system has selectable 2WD high, 4WD auto, 4WD high, 4WD low

 

[WXman]

My KJ was an early model with the 3.7L with the 4 speed out of the Dodge Ram (two 2nd gear ratios). In 2003? They switched transmissions to a more efficient unit. The joys of early adapters!

I saw around a 1MPG drop when left in Full Time (AWD) mode versus regular 2WD. Which is why I just left it in 4Full for so long.

The KJ originally had the 545RFE which was technically a 5-speed automatic, though Chrysler called it the "multi-speed" automatic because as you noted there were two 2nd gear ratios depending on whether it was accelerating from 1st gear or downshifting from a higher gear. They also used that transmission in 2005 and 2006 if you ordered the diesel engine. Otherwise, the other KJs got the 42RLE which sucked.

There should be zero MPG change between 2WD and 4-Full Time settings on a KJ because the front half-shafts and driveshaft spin 100% of the time on those Jeeps (and most others too) regardless of mode.

 

[wanderer]

Rock-Trac is great...........if you're in the rocks.

On every other terrain it sucks. Most guys hate it. Snow, mud, sand, water crossings, etc....you don't want to be crawling like a snail with a broken leg.

Really rock trac sucks? I didn't know! I have it and love it because when the s hits the fan it will get you out. and going down steep hills I like the control a 4:1 low gives. So why is select tract or something else better?

 

[Thau]

Select Trac was/is great because you can drive around with the 4WD system engaged all the time and you never had to worry about it. The ratio in 4 low isn't as steep but for all other situations the select trac should be just as good as any normal 4WD.

 

[The Great Grape Ape]

Yeah, the biggest benefit for 4:1 ratio is hill descent IMO. I prefer using engine braking vs actual brakes., even on tarmac I'll gear down to 3rd or 2nd.

As for getting you out of things I've never had issues with either really, and locking axles and even more importantly good tyres, makes the most difference I've found. I find 4:1 going uphill or flat ground a little less important, and while it can allow you to feather through/over some obstacle easier, I've never found a situation where I had to back down due to the 2.72:1 of the Command-Trac. But I have had rear lockers on all my JKUs.

Sure I still miss having all the Extras of my previous Rubi, but I don't think it's as important as the tyres and proper driver awarness/control. But it does make me miss it going down steep ski-hill service trails, especially when they are snow covered or muddy/rain-slicked, cause I want every bit of help then.

 

[Bearded_Dragon]

Really rock trac sucks? I didn't know! I have it and love it because when the s hits the fan it will get you out. and going down steep hills I like the control a 4:1 low gives. So why is select tract or something else better?

Correct me if I'm wrong as I've never had a Rubicon, but with axles unlocked isn't it an open differential? Granted BLD (brake lock diff) will help but I think people prefer LSD for mud, sand, snow, everything but rocks.

 

[The Great Grape Ape]

Correct me if I'm wrong as I've never had a Rubicon, but with axles unlocked isn't it an open differential?

That's correct, but he's talking about controlling the pace of the Wrangler more than wheel power distribution (which is also a factor of the Rubis lockers vs LSD vs Open/BLD)

Granted BLD (brake lock diff) will help but I think people prefer LSD for mud, sand, snow, everything but rocks.

This part is a hot topic, and has many multi-page raging threads in other Jeep forums.

For my usage and experience, which is gonna be different from someone else's preference, here's my take/preference (again proper tyres [type & inflation] often play as big or bigger a role);

LSD is preferable on light snow, and variable condition tarmac (rain, snow, ice), and then the default for mud and sand.

However when things get deep or loose, like 2ft of fresh snow, then that's when I like to go lockered. And deep mud and very loose sand are great with lockers, especially if you can lock-up in 2Hi and 4Hi with tuners/programmers or dedicated add-on lockers (this is a method best left for the experienced, because you can do serious damage to your Jeep and also cause serious control issues if you don't have complete control and familiarity with this type of driving). Speed can be really effective for mud, and sand, and some snow, the issue becomes identifying which is which and what needs speed and what needs deliberate lumbering pace to have the greatest control of forward progress to maintain traction/momentum.

Also I find very slow & deliberate 4Lo locked progress on slippery surfaces keeps me in control longer and in contact longer, rather than having to wait for the LSD to kick in after the fact, thus losing grip first before regaining it once the over torque spin to the free wheel activates the LSD after the fact.

Some people also don't like the characteristics about how the LSD engages and find it intrusive/distracting and cause loss of control for some (not my main concern, but a common complaint). I prefer the LSD on the snowy highway, but some people don't like the way it interferes and changes torque delivery. IMO it's still not as intrussive as BLD or traction control which I hate as it often gets in my way, like it did on awesome winding road in Vancouver island last month when I had to remembe to disengage after the first intrusion after stopping for pics or ice cream or whatever and turning the Wrangler off/on again.

For me, I would love to have the LSD + Locker combo of old TJ Rubis, that is also still offered on Eaton JK upgrades. It would offer the best of both worlds for me where I would use LSD on the variable condition tarmac, and then lockers when going up the deep snow on the ski-hill service trails or for back-country skiing / off-roading.

That's my takes. As ever, your mileage / experience / preference may differ.

 

[geospyder]

...I prefer using engine braking vs actual brakes., even on tarmac I'll gear down to 3rd or 2nd...

I tend to use the brakes coming up to a stop light. Reason being is something an instructor once asked me when I was racing. He asked me "What is the easiest to replace - brakes or clutch?"

 

[The Great Grape Ape]

Never had an issue, but then again my vehicles usually only last about 50,000 miles / 80,000 KMs before I upgrade them.

Also, even on the Autos I brake first (despite it really only being an issue for manual), set a good speed & mid range RPM in lower gear first, then coast it down on engine braking, so not just throwing it into gear and shocking the system.

In off-roading it's usually from a stop or nearly so after transition to 4Lo to begin with, so clutch shouldn't be an issue.

BTW, nice Wrangler, had a similar 2010 as the cottage Jeep before the Baja JKS.

 

[Eugene the Jeep]

Can we assume that this is Selec-Trac (and not Selec-Trac II) that we're getting? I wouldn't want Selec-Trac II.

The more full blown Selec-Trac has all the modes - 2H, 4H Part Time, 4L Part time, 4H Full Time and N. Selec-Trac II has 2H, 4WD Auto and 4L.

 

[Vegas_Sirk]

I tend to use the brakes coming up to a stop light. Reason being is something an instructor once asked me when I was racing. He asked me "What is the easiest to replace - brakes or clutch?"

Yea thats a commonly said thing around the paddock, my instructors told me the same thing.

 

[sjl136]

Please excuse me if these have been answered or are ridiculous questions. Can we expect the Selec-Trac to be offered with the 3.0 diesel? How about the 6spd manual Pentastar or does Selec-Trac play with the autos only?

 

[WaltA]

Please excuse me if these have been answered or are ridiculous questions. Can we expect the Selec-Trac to be offered with the 3.0 diesel? How about the 6spd manual Pentastar or does Selec-Trac play with the autos only?

Since SelecTrac will be offered on the high-end Sahara model only, I would venture a guess that it would be autos only.

 

[sjl136]

I could see Jeep and dealers using the Sahara 2.0T / Selec-Trac combo to attract the market interested in the most cross-over like Wrangler (that felt dirty to even type). Up until reading through this thread, I was dead set on a diesel JLUR. But now I admit to being intrigued by the Sahara Selec-Trac for New England weather and the amount of time I spend driving to and from the ski slopes. I still want weekend wheeling capabilities, a mild lift, KO2's, usable off-road add on's, and would love to make it to a Jamboree with it, so can't wait to hear how the early Selec-Trac JLU's do on the trails before making a final decision.

Sponsored