Hey guys,

'90 4runner 5-speed 4x4 here. 22re and W56 tranny.

Purchased a couple of years ago. Here's the problem:

When I shift into first gear slow, all is well. When I say slow, I mean physically moving the shifter up into 1st from neutral, slowly and smoothly.

If I move it up into 1st fast, I get a grinding thunk sound. No other strange noises from the tranny. It is butter smooth and quiet in all other regards. Replaced shifter seat and socket bushings with Marlin Crawler parts a while ago and has no bearing.

When looking up this issue, some folks point to a worn clutch, but I'm having a hard time wrapping my mind around that - if a clutch is worn, it would still separate from the flywheel enough to disconnect tranny from engine to avoid the 'clutch engaged while trying to mash gears' situation, right? In my mind, the clutch wear issue would result in a 'clutch not engaged enough' (resulting in slippage) rather than a 'clutch still engaged' (resulting in grinding gears)? Please correct me if wrong or not thinking it through.

I believe my clutch pedal is adjusted correctly, but clutch has unknown miles on it. I felt it slip for the first time yesterday in 4th with moderate pressure on gas, so I'm wondering if a collapsed pressure plate may be factoring into this. I'm not getting this fast shift grind in any other gears, so I'm wondering if it could be the syncros?

Basically, I'm trying to isolate the tranny issue to see if it is with the tranny alone or if the clutch has something to do with it. Unknown history on clutch master/slave cylinder fluid and tranny fluid. I am going to be doing a tranny fluid change with some GL-4 stuff. I'll check the master/slave cylinders.

Any thoughts on this? I'm betting that I have some deferred maintenance to take care of but trying to figure out if this is a syncro issue, fluid issue, clutch issue, or something else. Again, the gear crunching only happens from N to 1st and only when slamming it into gear medium to fast speed.

Thanks for any help and or thoughts guys!

 

Assuming it's not the clutch, and it likely isn't, first, make sure you're using GL-4 gear oil, not GL-5. GL-5 is often too slick for the synchronizers and is best left to the differentials.

If you have the correct gear oil, then it's most likely a worn synchro. When the synchros and balk rings are working correctly, it should be impossible to cause the gears to grind. The synchro rotates the balk ring into position keeping the gear collars from trying to mesh until the shaft speeds are the same. With a worn synchro, there's not enough pressure and friction to positively rotate the balk ring into the balk position, so you bypass the mechanism and get grinding.

First gear is the hardest gear to synchronize, because of the wide speed difference in the input and output shafts. On mine, first is very hard to shift into unless I'm stopped or I double-clutch correctly.

As long as you don't mind taking it easy, or learning to double-clutch first gear, there's no immediate need to do anything. A proper fix will require pulling the tranny apart.

 

I recommend Redline MT 90 gear oil. Check your clutch adjustment. I recently did mine. It helped. Also found the return spring wasn't on. Mine would occasionally crunch into third.
https://www.yotatech.com/forums/f116...w-pics-291259/

 

I am not sure what your issue is on your transmission so am not commenting on that.



What I am commenting or more of a question, for some reason and I don't understand why, but a clutch will slip in the higher gears such as 4th and 5th. You would think it would slip more when it is sitting still and having the most resistance to moving.

I have had clutches to hold when taking off hard or fast and not slip in the lower gears, but when accelerating at a gentler speed but in 4th or 5th gear they will slip when bad.

If you try accelerating hard in the higher gears and it does slip, I feel the clutch could be part of your problem but maybe not all of your problems.

 

It actually makes sense when you think about it. Keep in mind that the clutch only cares about the engine torque load, not the vehicle load. When you are in 1st gear, the torque load on the engine (and therefore the clutch) is fairly light. Think of how quickly the engine will go from 1000 to 4000 rpm when you accelerate in 1st gear. That's because the engine torque load is light. The gears are doing all the work, multiplying the torque to the rear wheels.

Now put it in 4th and mash on the accelerator. The engine winds up much more slowly, not because it has less power, but because the gear ratio is so much higher and it takes a lot more engine torque to accelerate the truck. This torque is transmitted through the clutch, and if the clutch is marginal, that's when it will slip.

Think of it like wrenches. 1st gear is equivalent to a 4 foot cheater bar. Doesn't take much effort to put 100 ft-lbs on a bolt. 4th gear is like a 1 foot ratchet handle. Now you have to really put some effort into that 100 ft-lbs.

 

The quick way to check for a bad clutch IS to put it in 4th and try to move from start. The truck should stall or buck. It should NOT rev up, illustrating the clutch slippage.

I'd start with making sure the clutch master and slave are bled really well. But if you're experiencing slippage, you may as well expect the clutch is due if not already required.
Buy Aisin clutch master AND slave, not generic Chinese cheap stuff. You WILL replace the junk sooner than you think it's just not worth it. I learned this by doing it.

And get a good clutch kit put in, then bleed the heck out of it. Put in fresh gear oil in the trans, make sure it's full and no leaks. Confirm your pedal bracket is good, and you should be set for 100k.

 

Thanks RJR, I do understand it when you explained it that way. I was talking to a friend of mine recently and we were thinking the higher gears should be less pressure but I see it your way. Thanks again.

 

I filled my trans in my '92 4runner, 22re, w56-c with a GL-5 (claims GL-4 compatible), synthetic today....after further review I think I have a R150F or 151. Took it out for a drive and it seemed to be shifting fine. Got home, parked and when I went to go out later in the day I couldn't get the truck into gear. After doing some reading I am planning on swapping my oil tomorrow and saving the old stuff for diffs. Could the change in oil really mess up my tranny that badly...and that quickly? I went out twice this morning before changing it and had no issues.

I also pulled the shifter this afternoon after I couldn't get it in gear and my shift lever bushing/seat was basically non existent...just a bunch of crumbles....so I'm assuming that could have contributed too.

I have to wait till my wife gets back from being out of town to check my slave cyl to make sure it's working right, but I just got the truck about 3 months ago and I bled the master and put in new fluid after getting it...no problems there since.

If I get the seat put back in, refill with GL-4, and the slave appears to be functioning appropriately then it is likely the clutch correct?

I checked the pedal and it seems to be within adjustment, and I don't see any cracks in the bracket.

Does anyone know if the HD shifter seats from marlin require the use of the rubber gasket/bushing under it in the shift lever assembly? I'm thinking of going that route just to avoid dealing with anything similar in the future.

 

Oftentimes my 4Runner is also difficult to shift into first gear from second gear when truck is moving, even at a very slow crawl. It is not a hard resistance but I'd feel some light grinding and I back ff right away when I feel it.

I first noticed this when going uphill when off-roading where I needed to downshift. I tried double-clutching but that does not seem to help. Need to try some more.
Meanwhile:
1) I had bled clutch master cylinder, and cutch feels like it did when it was first replaced. No leak.
2) Distance from floor to top of rubber pad on clutch is 6 inches; slightly higher than on FSM, but then again, the floor metal is corrugated, so I'm not sure whether to measure from ridge or valley. Free-play feels good.
2) The part clutch fork travels half-inch, when clutch is depressed all the way. I could not find specs for it in the FSM. Would appreciate if you could point it out (what page/section?).
3) Transmission was rebuilt in 12/30/2016 approximately 58,000 miles ago. Before that I had Redline MT-90 GL-4. I do not know whether rebuilder reused the oil or filled it with GL-5.

I do not have difficulty in shifting into other gears, including reverse. Because difficulty is only when moving, does it sound like a synchro issue. I'll try replacing trans oil with GL-4 again. After all, it had been almost 60,000 miles since rebuild.
Thoughts, please? What else should I check? TIA!


Clutch Check from FSM

Clutch Fork Travel is 0.5 inch

 

Try bleeding the system overnight, press the clutch pedal with a extendable broom stick or similar and leave it that way all night, air bubbles will go up to the reservoir.
No cracks in the pedal bracket? Maybe the crack is not large, but probably can be seen opening slightly upon use.
5mm (0.20 inches) solved same problem in my 4R (with asphalt sheet under the carpet):
https://www.yotatech.com/forums/f116...oothly-309564/
The clutch fork travel in my 4R is 0.6 inch.
Are the shifter seat and socket in good shape?
Double clutch it?