Toyota Low Gear Lurching

[ricsrx]

My truck was not that bad, but changing the t-case mount to the TG heavy duty item, as allready mentioned made a huge difference, the down side was the transfer of vibration to the cab.

 

[sixstringsteve]

Have you tried it in 4-lo with the rear driveshaft removed (only front-wheel drive)?

With the driveshaft spinning but not the diff, I'm guessing it's in your rear third member. I've never seen a truck lurch like this before. 2 full turns of the driveshaft without wheel movement is way off. I'm guessing you're missing teeth on the ring and/or pinion, and/or your backlash is WAY off. Has the pinion nut loosened?

 

[sixstringsteve]

what kind of locker do you have in the back?

 

[Kevin B.]

Reviving this old thread. Spent some time looking into this again yesterday. I have since replaced my factory springs/lift block setup with Chevy 63's in the rear...not a lot of change in the lurching. I found a nice flat spot and let the truck drive itself and watched it lurch pretty regularly. I then watched the correlation between the rear driveline, the rear diff, and the tires. What I saw, is that when it is about to lurch, the tires pretty much stop, while the driveline spins almost 2 full revolutions, and then the tires lurch forward as the diff finally transfers power to the axles. Which means, that something is off inside the rear diff, just not sure what yet. When I get back from Moab next week looks like I'll be pulling the third.

I'm having trouble picturing the kind of slack required in the third to let the shaft rotate twice without the tires moving. Are your side gears made of rubber bands?

 

[clfrnacwby]

Have you tried it in 4-lo with the rear driveshaft removed (only front-wheel drive)?

I don't believe I have. I am flat towing it to Moab this week so the rear driveshaft has to be removed. When I get to camp, I'll test this out before I install it again.

With the driveshaft spinning but not the diff, I'm guessing it's in your rear third member. I've never seen a truck lurch like this before. 2 full turns of the driveshaft without wheel movement is way off. I'm guessing you're missing teeth on the ring and/or pinion, and/or your backlash is WAY off. Has the pinion nut loosened?

Yes, this is definitely NOT normal. I'll check the pinion nut this week as well. I can't wait to solve this mystery.

 

[clfrnacwby]

what kind of locker do you have in the back?

It's a full Detroit.

 

[clfrnacwby]

I'm having trouble picturing the kind of slack required in the third to let the shaft rotate twice without the tires moving. Are your side gears made of rubber bands?

You'll get to see it first hand, it's a trip. If something was really wrong with the 3rd, I'm assuming it would have grenades by now. Maybe those rubber bands are magic...

 

[sixstringsteve]

i wonder if the locker is broken. Knowing how they ratchet, I wonder if it could be storing energy and unloading all at once? I'm excited to see what it is.

 

[clfrnacwby]

Ran another test this morning with the rear driveline removed, both t-cases in low, both front hubs locked, and the e-locker disengaged. Yes...there was lurching. Argh. On the bright side, my rear diff is probably just fine . The behavior is pretty similar. It crawls along fine and then all the sudden the tires seem to "stop", while the driveshaft continues to spin...then it lurches forward. It does not lurch with as much force as the rear (probably due to the difference in lockers), but it still does. At this point, I'm assuming there has to be something wrong with the drivetrain. Could a clutch be causing this somehow? It has been making some noise lately. I guess I'll have to pull both cases and inspect the gears. While it's all out, I'll look at the clutch as well. It has the Marlin HD clutch, I'll see if there is any warranty on it that I can take advantage of.

 

[Kevin B.]

You've already ruled out the clutch, though, by watching the driveshaft wind up against the diff.

Not that I have any idea what's doing it though. Watching the shaft spin while the tires don't is uncanny, and makes me want to hire you an exorcist or witch doctor.

 

[sixstringsteve]

can you get a video of the driveshaft twisting without the wheels turning? I've gotta see this.

 

[clfrnacwby]

I'll see what I can do...it's a trip, for sure.

 

[cuban b]

every vehicle I've driven with really low gears and a MANUAL trans reacts this way. It just jumps into motion so easily, then is wound up so quickly that it lurches. I do it for fun because my kids think it's hilarious.

Is your buddy's rig a manual? I could be wrong if the lurching is extreme, but it's not your clutch and I have a hard time thinking a broken diff would tolerate much of that.

Old drivetrains get a surprising amount of slop. My old sami buggy has quite a bit of rotation in the driveshafts before things actually move.

 

[sixstringsteve]

I've had a handful of trucks with super low gears and a manual, and none of them lurched. And they DEFINITELY never did anything like Andrew's truck does. It's the weirdest thing.