Toyota Low Gear Lurching

[clfrnacwby]

I've got an '88 4Runner SAS'd. Quick specs:

22RE w/ 5-speed manual and HD Marlin clutch
5.29's front (4cyl) and rear (V6) with a Lockrite in front and full Detroit in rear
Dual cases with 4.7's in the rear
37" MTR's

Problem:
When I'm in 4WD using Low/Low or even High/Low (High in the crawl box) and I'm trying to crawl, as soon as I hit rocks the truck lurches/bucks horribly. I've tried to keep my foot steady on the gas and even ride my brakes with the other foot, but it doesn't help much. I crawl towards the rocks and as soon as the tires hit, it almost stops the truck dead in its tracks and then lurches forward. The rocks don't have to be more more than about 6" tall before it starts. To minimize this I have to be on/off the gas every second to accommodate the obstacles.

My buddy has a Tacoma with the 3.4 and the same dual t-case setup and tire size, and he can simply idle through the same rocks - truck NEVER lurches or bucks - even if he's going up or down a 4' rock wall. I've been wheeling Toyota's for over 10 years now so I'm not new to this. I am new, however, to the dual t-cases. Anyone else experience this? Could my clutch or tranny be going and causing this?

It's gotten so bad that I'm considering selling it and moving to a rig with an auto tranny in it...

Thanks!

 

[tony moniz]

my toyota has duals(stock gears in both),39" iroks and 4.10 axle gears. it doesn't lurch. i do ride the clutch alot though to compensate for not enough gearing so it might and i just drive around it. but my old mans jeep does it bad in low range(stock cases and 3.73 axle gears and 35" mtr kevlars) and i don't like to drive it to often because of it. mabey if you figure out the problem with yours it will help me figure out the jeeps problem(besides the obvious.haaa)

 

[chans]

I would guess the clutch. When the flywheel surface isn't completely flat with a high friction clutch it chatters and jumps under high load. Does it do it when you dump the clutch on a dirt road?

 

[Marsh99]

I have dual case with 2.28 front 4.7 rear and in low low, I don't have that problem.

I would think it was your gears switching from coast to drive... maybe to much backlash?

 

[SLC97SR5]

It could be backlash in the R&P and even a bad t-case or engine mount. They are taking a beating with that deep gearing.
Does the engine load up when you encounter obstacles? If so, check your timing and increase your idle. I bump my idle up when airing down my tires and it makes for much smoother transitions since the engine doesn't have to lug as low in the rpm range.

 

[clfrnacwby]

It's does load up in the sense that it bogs down really quickly when encountering obstacles. So, I'll be checking the timing...which I needed to do anyway since it was pinging horribly when trying to drive 45MPH+ on the freeway.

 

[sixstringsteve]

with that low gearing, you should be able to idle up everything without having to touch the gas... I'm curious what it ends up being.

 

[clfrnacwby]

So with the engine running and tranny in neutral, the crawl box in High, and the rear t-case in 2 Hi, I grabbed the rear driveshaft and tried to twist it. To my surprise, I could actually move it quite a bit before I saw the rear tires starting to move. If I had to estimate, maybe a 1/6 of a turn? Shouldn't that thing be solid? I couldn't believe there was that much play with the t-case in 2Hi. Is that too much slop? I have heard of "some" slop being normal with the Detroit...

*Note, if I put the tranny in gear with the engine off, I can only move the driveshaft about half of what I can with it out of gear.

I put together a little video...

[video]http://s78.photobucket.com/albums/j85/clfrnacwby/Toyota/?action=view&current=IMG_0260.mp4[/video]

 

[Westernhunter]

Wow, that seems like a lot of slop. This was my first thought when you mentioned lurching. I had an old Ramcharger that lurched horribly until I replaced every u joint. I'd yank the third member and take a look.

 

[clfrnacwby]

Just checked my front end as well. Locked the hubs and twisted the front driveshaft. It almost goes a full 1/4 turn - a little worse than the rear. Looks like I'll be pulling both thirds and taking them somewhere to get the backlash checked.

Another thing I thought was odd is when I remove the rear driveshaft, start the engine and leave the tranny in neutral, the output shaft and flange on my t-case spins. Doesn't matter if it's in 2HI or 4HI or even 4LO. If I grab it with my hand, it stops spinning. If I put the t-case in Neutral, it stops as well. Weird...

 

[Spork]

Just checked my front end as well. Locked the hubs and twisted the front driveshaft. It almost goes a full 1/4 turn - a little worse than the rear. Looks like I'll be pulling both thirds and taking them somewhere to get the backlash checked.

Another thing I thought was odd is when I remove the rear driveshaft, start the engine and leave the tranny in neutral, the output shaft and flange on my t-case spins. Doesn't matter if it's in 2HI or 4HI or even 4LO. If I grab it with my hand, it stops spinning. If I put the t-case in Neutral, it stops as well. Weird...

Probably enough friction in the gear lube to make it spin, I wouldn't be overly concerned but I wouldn't be grabbing a spinning flange either.

 

[chans]

Up to 1/4 turn of play is normal for a Detroit locker.

 

[skippy]

I can take a look at those thirds for ya. it only takes a second to check the backlash.

 

[chans]

The video looks like normal play to me. Before you pull the thirds look in the Detroit manual.
Here is a clip from said manual.

These characteristics are normal because of backlash designed into the NoSPIN differential, which is of a fixed amount (1 to 2 inches of rotation at the tire tread).

Backlash or slack between the driving and driven clutch teeth is an inherent part of the NoSPIN and necessary to permit automatic operation when driving in forward and reverse. The total backlash in the driveline is increased by the amount of the reduction between the ring gear and pinion. If the ring gear pinion ration is 5 to 1, the total backlash in the drivetrain with the NoSPIN would be about 30° . This in turn is increased by clearances between planetary gear, sliding splines, and the ring and pinion gear. We feel that the total driveline slack can amount to as much as 1/4th turn of the driveline without being abnormal, but if it exceeds ¼ turn, other parts in the drivetrain could be checked. Further clarification of operational and performance characteristics is available through Technical Bulliten No. 81-1044. A copy is available by writing to our marketing department.

 

[clfrnacwby]

To follow up on this, after talking to a buddy, he mentioned axle wrap could cause this behavior so I checked my leaf spring U-bolts. Yeah, the fronts were VERY loose and one side of the rear was as well. Torqued everything down to 90 ft. lbs - I don't have it completely solved yet, but have mitigated the lurching significantly. The rear still has factory leafs and lift blocks so I think I'll still have a little axle wrap until I get that replaced with straight springs.

 

[clfrnacwby]

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.

 

[sixstringsteve]

so you've tried this without the front driveshaft on?

 

[clfrnacwby]

Yes, no change.

 

[sixstringsteve]

hm... i'd be tempted to swap out the third for a stock one just to see if that fixes it. i'll bet there are quite a few 4.10 thirds floating around out there that someone would sell cheap or let you borrow for a test.

 

[clfrnacwby]

Good idea. Luckily I have the 4cyl 3rd I just pulled from my front axle that I haven't put up for sale yet. It does have a lock right, but that shouldn't matter. I'll throw that in there and see if the lurching goes away.