letinsh

'87 waggy, 4.0, aw4, NP231, D30/35, 239k-ish

Over the last few months, especially in the cold, I've noticed that it has taken longer and longer for the transmission to engage when going from Park to Reverse or Drive (though it is noticeably worse going forward than going into reverse). Then, last week, whatever is slipping has started slipping while changing gears (1-2, 2-3, etc). It is a little better when manually shifting, rather than just kicking it to Drive, but there is still a problem (it also never seems to lock up).

Since I've owned it, I haven't changed the tranny fluid, so I did the Poor Man's Flush. 4 gallons of Dex III/Merk later, it's running nice and red. There's a little bit of improvement, but not much. (The fluid that came out was black as night - I'm slightly ashamed it was like that).

With clean fluid, I did the "How to test a torque converter" test found here. Hit stall at 2200rpm, which is right in the 2100-2400 rpm window it should be in, so that test tells me nothing.

Measuring the resistance of the 3 tranny solenoids, all three were ~17.4ohms, which is good by one spec and too high by another, but they were all very similar. Putting 12V to them causes a noise, which I assume is them actuating....
The ground in that circuit tested at .5ohms to the battery, so that's good.

The TPS tested fine (both in adjustment, ground circuit, and no "flat spots" through range of movement).
The TV cable is adjusted properly.

So where does that leave me? Torque converter? Tranny? Solenoids?
I'm stumped.

steelybill

Did the old fluid have any burnt smell to it ?? I'm no expert on these transmissions, but low pump pressure may not be applying enough pressure on the clutches etc, or the clutches themselves may be worn enough to slip with a load on them.
The shift cable may be out of adjustment, or the throttle cable may need adjusting, which can cause your problems, along with other things. A pressure test may show something.
You will need a manual if you get deeper into it...

letinsh

Honestly, it didn't smell bad enough to note, and now it's mixed in with a bunch of new fluid from the flush, so I couldn't tell you (that whole bucket is very pungent, though). The TV (throttle valve) cable is fine. The shifting is accomplished via linkage, not cable, unless I missed something along the way.
You might be on with the clutches....grrr...i don't like having this problem.

cruiser54

Do another fluid change. Dex/Merc fluid right?

ehall

Agreed, run it some and do another change. The slipping you describe is probably because seals aren't holding when its cold (shrinkage). Nasty fluid could explain some of it. You'll need to drive it to exercise everything on the valve body. Look in the fluid for floating particulate. If the clutch pads are wearing aggressively then you'll need some labor (swap or a rebuild). Light slipping will lead to destroying the clutches if it goes too long.

letinsh

Sorry for the late reply-was out of town.
I dropped the pan and replaced the filter. The pan didn't look bad at all, just a thin film of gunk. I was surprised how clean it was. The magnet had some stuff on it-not much, but no chunks. The filter had some particles, but, again, not much.
Cleaned everything, new filter and topped it off. On the way to work in the morning, it behaved perfectly but on the drive home, it was back to slipping.

Cruiser, should I do a full flush again or just drain the pan?

I'd prefer not to, I've been reading, and I think I can pull off a rebuild in a weekend...
(yes on the Dex/Merc)

DFlintstone

Radi posted a process to find if a problem is electrical, or mechanical. Unfortunately I didn't save the link. Basically it involved disconnecting your TCU entirely, and seeing if it then goes through the gears correctly, manually.

My .02 is if your fluid is nice and pink, (and fresh in this case), changing it might not help. It might take time for the detergent to work at deposits...Idk.

ehall

You could try some Trans-X, its legit for cleaning gunk from valves and seals, takes time to work though. Might not help but it won't hurt anything that is already broken. Don't use Lucas for this phase, it actually can hurt.

letinsh

DF, thanks for the reminder. On the drive in to work tomorrow, I'll pull the TCU fuse and see what that shows, though given what I've already checked, I'm fairly certain it's a mechanical issue. Thanks!


ehall, I've got a bottle of Auto-RX laying around. I've used it in the engine, but not the tranny. Any experience with it? I'll also look into that Trans-X.
Thanks!

DFlintstone

[QUOTE=letinsh;3010323]I'll pull the TCU fuse and see what that shows,


I think Radi knows about the fuse. He said disconnect the TCU. I sure don't know myself. Btw you can remove a few screws and lower the panel to reach it without removing the whole thing.

ehall

I installed a junkyard AW4 the same time I swapped engines (my stuff was +300k miles). It had some bad behavioral problems, hard shifts, irregular shift patterns, very fast shifts through second gear, stuff like that. I put some Auto-RX in with the first set of fluids and ran it about 1k miles, then changed fluid and added the Trans-X. Now it shifts like butter, very smooth, even in Power setting it is almost imperceptible. I added some more to my Cadillac trans that has problems with worn seals that led to clutch slipping, and it helped a lot but since it doesn't regrow anything it didn't fix the base problem, and I need to swap on that.

letinsh

Pulling the fuse accomplishes the same thing. I've been driving around these last couple days with the fuse pulled. The shifts are much crisper and the engagement is certainly faster, but there is still some slipping, particularly in first. I don't know if there is code in the TCU slowing down the shift to make it smoother (if that's even possible via code), but there is a change when shifting manually with the fuse pulled. Perhaps I should find a known good TCU to help troubleshoot this.

I just put 6oz of Auto-RX in, so we'll see how it goes. I don't have the time/money to tear into it just yet, so I'll get a few miles with it in there.

Thanks for the suggestions!

....now off to find a Renix TCU....

ehall

Auto-RX is a metal treatment, Trans-X is for the seals and valves, they do different things

DFlintstone

Check the TPS on the square trans side. It's actually two in one, and just one side can fail.

letinsh

That was the first thing I checked, and it needed a little tweak to get in spec, but it made it. I'll check again, though. If I set one (say I adjust the 3 pin connector to be in range) should the other be good as well? If they are different, do you find the best compromise, or is the TPS shot?