How to exercise 4WD with no dirt roads around

After re-reading it I am confusing things. You shouldn't and Toyota prevents you on electronic shifting t-cases from trying to make the front end come up to highway speed instantly. In the old trucks with manual cases you could in theory shift the thing at any speed you wanted at the risk of damage.

Once in gear you can drive as fast as you want. Of course practically speaking if the road is bad you probably shouldn't be going 70 anyway to need 4wd. But who knows, anything is possible. As long as you slow down so you don't grind gears too hard before engaging 4wd first. The only reason I could imagine might be asking the front drive of the t-case to spin at those speeds. That's not a problem for V8 4Runners, Cruisers or FJ Cruisers with full time 4wd but their transfer cases are designed for it and I don't know if the bearing oiling is the same.

The question here asked was indeed about 4wd on pavement. Which is ok if you don't turn. But it's still not good because with zero slip the difference in tire diameter, inflation, slight difference in ring&pinion ratios will eventually cause windup.

 

I think that you are still getting things confused. The truck has a rear differential, front differential, and the transfer case. The tires can spin at different speeds with no problem. When you engage 4wd you aren't locking any differentials. You can make turns in 4wd.

 

Wrong. The transfer case ("center differential") is locked. That's the fundamental difference between part-time 4wd (what we have) and all-wheel drive.

Edit for clarification: We don't have a center differential. Just the transfer case which provides a straight "locked" connection between the front and rear driveshaft when in 4wd. This is the only source of windup/bind unless you lock the rear diff. You are correct the differentials in the front and rear allow for varying wheel speeds across the axle. As in left front can rotate at different rate than right front. Same with left rear and right rear. However, what is not allowed in 4wd is the front driveshaft rotating at a different rate than the rear driveshaft. So cumulative front rotation must equal the cumulative rear rotation.

 

I don't see it that way. With the ADD, the front shaft, ring, and pinion will probably not be turning. I believe the ADD engages after the t case. So in fact, most of the front driveline does need to spool up to the speed of the rear.

You can make turns when on a slippery surface, but even on packed dirt, there is some bind that can be felt when turning tight like switch backs. Anything more than a lane change on pavement should be avoided.

 

Have you looked at this map?

http://maps.psiee.psu.edu/preview/map.ashx?layer=260

 

Like stated, long straight stretches of road even dry are fine, thats what i do on my truck.

They say 10 miles a months, but really you can get away with much less, mainly its to make sure the actuators dont stick, so even a 1 mile stretch is fine, just cycle it twice and you are good.

Also, 4hi can be put in at up to 60mph, but has no limitation as to top speed. Just like 4lo, has to be put in at under 3mph, but you can go as fast as you can (which will be revlimiter in top gear around 50mph).

 

A differential allows a difference in speed across it. There is no differential in our transfer cases, so the front and rear driveshafts must always be the same speed. When you turn the front wheels have to travel a greater distance than the rear, so the front driveshaft will turn faster than the rear for a given vehicle speed.

This video covers it and is done in a British accent, so you know he knows what he's talking about.

 

And I'm out

 

So here's a question I've always had. When driving in 2Wd the front drive shaft is not engaged so there's no load on it right. I know that but does it still spin since its connected to front diff witch in turn is connected to front wheels?

 

No. The ADD disconnects the front right driveshaft. There's a youtube video of this using a Tundra axle and t case.

So the CVs are spinning, but inside the diff it is just the spiders whizzing around. The ring, pinion, and carrier are generally still. This is why you can rotate the front driveshaft by hand to lube the zerks. That situation needs to be overcome when 4Hi is engaged while moving. It is more difficult on the system the faster the Taco is going.

This is also why it is a good idea to swap both diff fluids no matter how much 4wd use folks get.

 

Thank you for answering that!

 

No problem!

 

I just love how everyone that lives in Bucks County calls it NE Philly when it's a completely different county. (Used to live in Levittown, Pa and worked in NE Philly).

 

Remember the good old days when Toyota told us to go to a empty parking lot, engage the 4H, do 8 -10 figure 8s once a month.

 

I may be aging myself.

 

Was that one a 1st Gen with manual locking hubs? If so, that makes sense.

 

Yep. It rusted into little pieces, but the 4 wheel drive always worked.

 

I still wish that I got one back then. Around here, it'd be in great shape. There's a ton still on the road. I can't say what the frames are like, but the weather is easy on cars.

 

I throw it in 4Hi whenever I remember to. Dry roads are fine as long as you're not making 90 degree turns. Gentle sweeping turns are fine, road doesn't have to be arrow straight. If driveline is starting to bind you, you will quickly feel it.

 

Any updates from the cousin?