Shift on the fly... (1 Viewer)

[MrMoMo]

Ok, did a search and didn't really come up with what I was looking for.

Planning on picking up my first 40 this weekend. Will likely be driving in mixed conditions on the way home, snow and dry pavement. My question is, at what speeds can I safely shift from 2hi to 4hi, and do I need to clutch when doing this?

I am used to driving my '99 Tacoma, it is reccomended not to shift INTO 4hi above 40Km/h but does not give a speed for shifting out of and I regularly do it over 100km/h. It is an auto so I don't clutch for anything. Am I safe to assume the same in a 40?

I don't like the idea of driving on dry pavement in 4hi at highway speeds, but I also dont like driving in snow in 2hi at highway speeds!

any input would be appreceated.

Thanx

Bruce

 

[CruisinGA]

What year?

vacuum tcases are shift on the fly 4wd. I wouldn't hesitate at any speed.

No cases are shift on the fly hi/low

i would just let off the gas.

 

[Poser]

vacuum tcases are shift on the fly 4wd.

What would be the difference between vac and mech, other than the means they are controlled?

 

[DSRTRDR]

in my truck, that doesn't work. 4WD wouldn't engage unless manual (Warn) hubs locked, and doesn't come out of 4WD unless hubs manually unlocked. I don't shift 4hi to 4lo on the fly, either. But I do have 2lo thanks to that expert PO some 10 years ago!

 

[Mace]

I have shifted into 4hi at 70 before...

 

[Pin_Head]

It will shift in and out of 4w any time, but it is pointless if the hubs are not locked. You can also shift from lo to hi and back but you have to match the engine speed with the output shaft speed or it will grind a lot. No clutch is needed, just like old time non-synchro trannys. This is not recommended unless you are real good at this.

 

[subzali]

it will NOT shift into 4wd without the hubs locked. Before I knew how it all worked I tried it on my dad's Tacoma. It just buzzed the gears so I quit until I learned more. Once the hubs are locked you're golden, just let off the gas, just did this the other day at about 45. I guess shifting back and forth from lo to high would be like shifting the tranny without the clutch, when downshifting you have to rev the engine up to match the tranny like pin_head said.

 

[surfpig]

Here's my understanding (for what that's worth): when driving in iffy conditions (wet, muddy, snowy, dirt roads) engage the front hubs, then use 4hi when necessary. Shifting on the fly is fine in these conditions. As long as the axles aren't binding up, you'll be fine. That's what I do, let off the gas a bit, shift the transfer, and go. I think I push in the clutch, not sure it's necessary, just to be cautious.

Enjoy,

nial

 

[CruisinGA]

What would be the difference between vac and mech, other than the means they are controlled?

Toyota thought there was a difference...


Probably cause the vacuum isn't going to put that much force on the collar, so it will just slip in when aligned, but a person is going to try and force the mechanical lever...

At least thats my take.

 

[Doug_S]

It has been my understanding that, since the TC isn't synchronized, there could be some hard done when shifting "on the fly" from say 2h to 4h. Interesting discussion. I've always stopped and shifted the TC. Maybe I'm just being overly careful.

Best regards,

 

[subzali]

If your front and rear driveshafts are spinning at about the same rpm (going straight with minimal slipping at tires) then you don't need any synchros, the shifter will just fall into place. As far as pushing in the clutch, if you're moving then your rear driveshaft/transfer/tranny are still spinning at rolling rpm, so I don't think that makes any difference as far as engaging the front axle is concerned. Pushing the clutch in just allows the engine to rev down to idle. Just my .02.

 

[oldman]

For years I have locked the hubs at the start of winter and not unlocked them until spring. I regularly shift in and out of 4WD with no problems.

 

[Gundy]

old timer

Warn's old Lock-a-matic hubs are on my 72 fj40.
I shift in and out of 2wd to 4wdH without problems.
The hubs auto lock so it really IS going into 4wd
with the shift.
Serious wheeling duty requires the hubs to be manually locked.

 

[MrMoMo]

Thanks for all the replies, it is a '76 - and it seems to me that as long as I have the hubs locked (obvious to me) and the conditions are iffy, it's OK to shift on the fly as long as I am not spinning the rears.

Thanks!

Bruce

 

[Varty Yo]

hey bruce did yah ever pick that 40 up you were askin bout............if so what was the final price

 

[MrMoMo]

Hopefully going to get it this sunday.... will let you all know the final price and post some more pics once I get it.

 

[Varty Yo]

best of luck dude!!!!!!

 

[timbercruiser]

The only real advantage to "shift-on-the-fly" 4WD is that you don't have to mess with hubs.

I used to shift in and out in my 89 P/U all the time with hubs locked

 

[MrMoMo]

I'm only planning on using it in varing winter conditions, my road is plowed less often than many of the roads I use to get to work, (some will be bare and dry when my road still has snow.) I just wanted to make sure I didn't have to get out 5 times on the way to work!

Thanks

 

[okie]

how fast can u go in 2hi and locked hubs?