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Servicing my old AW4

J Pugh

NAXJA Forum User
Location
Raleigh, NC
I have 98 XJ, with a pretty fresh stroker, only like 7k on it now. The Jeep had 265k on it when I bought it blown up, and since it's been back on the road with the new engine, it seems to drive great. I've never had an automatic before this, so maybe I don't really know - but, it seems to shift smoothly enough. Only issue seems to be that when I'm in 1-2 I only get 1... But I'm not sure how that's supposed to operate really, not very concerned with that though. So, more or less, it drives well.

Considering, however, the totally mistreated and ignored maintenance state it was in when I got it, I am certain nobody has serviced the AW4 for probably over 100k. I would jump all over changing the filter and flushing out all of the old fluid, but after reading online some, it seems possible that whatever old fluid is in there, with all of the old clutch material suspended in it, is the only thing keeping it going. But that's no good, I don't want to go on running a shitty old used up AW4 into the ground, I want to prolong it's life as best I can, make it clean and happy, and not worry about just how close it is to the end.

So, I just wanted some opinions on where that puts me, what I should do...

Thanks.
 
Unless you are equipped to do a flush (or can afford it at a tranny shop) I'd change filter and add fluid and run it a while. Then check the color etc. and proceed from there. I'd suspect it will take more than once to get decent fluid in the unit.

I've never had a Cherokee with an auto but that's what I'd do with any auto that had your history.
 
A safe alternative to a flush is to drop the fluid in the pan, fill with fresh Dex/Merc III compatible. Drive it for a week, then repeat the process a number of times until the fluid stays a nice red with no burnt smell to it. Then I'd drop the pan and either clean or change the filter and you should be good to go.
 
I have 98 XJ, with a pretty fresh stroker, only like 7k on it now. The Jeep had 265k on it when I bought it blown up, and since it's been back on the road with the new engine, it seems to drive great. I've never had an automatic before this, so maybe I don't really know - but, it seems to shift smoothly enough. Only issue seems to be that when I'm in 1-2 I only get 1... But I'm not sure how that's supposed to operate really, not very concerned with that though. So, more or less, it drives well.

Considering, however, the totally mistreated and ignored maintenance state it was in when I got it, I am certain nobody has serviced the AW4 for probably over 100k. I would jump all over changing the filter and flushing out all of the old fluid, but after reading online some, it seems possible that whatever old fluid is in there, with all of the old clutch material suspended in it, is the only thing keeping it going. But that's no good, I don't want to go on running a ****** old used up AW4 into the ground, I want to prolong it's life as best I can, make it clean and happy, and not worry about just how close it is to the end.

So, I just wanted some opinions on where that puts me, what I should do...

Thanks.

Reports from the field tend to indicate that a "power flush" of the AW4 isn't a good thing (although I've never tried it.)

I'd say to buy a case or two of Dex II/IIE/III/V, a filter kit or two, and do this:

- Drop the sump, clean thoroughly. Do not dismount the valve body. Clean the magnet in the pan thoroughly. Replace magnet. Clean the crud out of the sump pan itself. Replace the filter. Wipe clean (lint-free rag - if you don't have that, don't bother. "Lint-free wipes" for electronics are excellent for this) Clean mating rails. Install new gasket. Install pan (replace lost screws with M6-1.0x15 or M6-1.0x20. DO NOT OVERTORQUE SUMP PAN SCREWS! I've not used RTV on the gasket, I've never needed to. You may if you like.) Fill with four quarts.

- Put 5,000 miles or so on the box, drain & refill (don't drop the pan, don't do anything with the filter.

- Repeat.

- Repeat.

(This should get most of the loose crud out gently.)

After another 5K, pour a pint bottle of Berryman's B-12 "Chemtool" into the transmission, drive it around for 2-3 days normally, drain, and refill. (This will start to get the crud that isn't loose.) You may drop the sump & inspect the filter at this time (I'd suggest it, but it's not strictly necessary. If you want to monitor progress through this process, drain the fluid such that it will run over a coffee filter - it has enough "tooth" to it that it tends to catch a good sample of crud that flows over it.)

The reason for all the changes is simple - unlike with the engine, when you pull the sump plug on the transmission, you'll only drain about half of the fluid ("dry fill" on the AW4 is about eight quarts, most of which ends up staying in the torque converter. Drilling the case is typically required to empty it.)

The reason to do it gently is that most slushboxen will end up "adapting" to the crud they collect (until they don't work!) and you have to give them a chance to "adapt" to getting rid of it. If you blow it all right out at once, you'll end up screwing something else up (not deliberately, it just usually happens that way.)

NB: Like your engine, drain the transmission hot. This ensures that the maximum amount of crud is still suspended in the fluid when you drain it.

As far as the only getting first gear in the 1-2 range, this is normal for the AW4 - the controller "forces" it into first as soon as it can do so. No, we don't know why. Going to a "manumatic" controller (there are a few available) will give you the option of driving it as an automatic or as a "clutchless manual" with full control of the four gear ranges. There are a few designs out there - we have one or two sponsors that have the things, and you can also find them on Toyota enthusiast's boards (the AW4 is a Toyota design, and was known as the "30-40" or "A340" series by them. It was used in Celica, Supra, Toyota pickup, and some RWD Lexus models. I believe there is a five-speed version extant, but I'm not sure about swapping the one for the other - the controllers are certainly different, and you would have to have the five-speed have a standalone controller or know the truth table for the solenoids to build a manual shifter for it. The five-speed variant is predominantly Lexus, but I think it's also in the Landcruiser and Highlander.)
 
I did a poor-man's-flush in the drive way. I am not sure if it helped but it sure did not hurt. I ran 12 quarts of ATF through it twice in about 3,000 miles. Maybe it was not necessary to do it twice that quickly but peace of mind could do wonders.

1) Get a catch can that could hold at least the amount of fluid you plan to replace.
2) Get a good funnel that fit the oil filler neck on the AW4.
3) Remove the hose that take the fluid from the AW4 to the radiator oil cooler and
put it in the catch can. The out hose come off the front of the AW4.
4) Start the engine. Oil will be pumped into the the catch can. Replace the oil while it
being pumped out at about the same quantity it is being pumped out. Be careful
not to allow the AW4 to run low of oil. Stop the engine if necessary and add oil.

When I did mine, I was able to compear the the amount of fluid out verses the amount I replaced. In that way I never let it get too low and ended with the last of the 12 quarts to bring it up to the proper operating level.

Prior to doing the fluid flush, I had to remove the pan to replace the shift solonoids. Looking at the filter, (it is a very good quality bronze wire mesh reinforced screen) I think it is un-necessary to service the filter unless there are broken parts or plenty of sludge in the pan.
 
I did a poor-man's-flush in the drive way. I am not sure if it helped but it sure did not hurt. I ran 12 quarts of ATF through it twice in about 3,000 miles. Maybe it was not necessary to do it twice that quickly but peace of mind could do wonders.

1) Get a catch can that could hold at least the amount of fluid you plan to replace.
2) Get a good funnel that fit the oil filler neck on the AW4.
3) Remove the hose that take the fluid from the AW4 to the radiator oil cooler and
put it in the catch can. The out hose come off the front of the AW4.
4) Start the engine. Oil will be pumped into the the catch can. Replace the oil while it
being pumped out at about the same quantity it is being pumped out. Be careful
not to allow the AW4 to run low of oil. Stop the engine if necessary and add oil.

When I did mine, I was able to compear the the amount of fluid out verses the amount I replaced. In that way I never let it get too low and ended with the last of the 12 quarts to bring it up to the proper operating level.

Prior to doing the fluid flush, I had to remove the pan to replace the shift solonoids. Looking at the filter, (it is a very good quality bronze wire mesh reinforced screen) I think it is un-necessary to service the filter unless there are broken parts or plenty of sludge in the pan.

You are essentially correct about the filter - but if the transmission has been neglected, the inside corners of the filter casing will collect crud - and it will break loose as you replace the fluid (and for a long time afterward.)

Best to replace it outright before doing any major flushing, then PRN for varnish/crud/filings/parts/whatever afterwards. Make sense?

If you're going to get rid of crud, but you're not going to tear it to bits and clean each bit individually, you may as well get rid of as many reservoirs of crud as you possibly can. Changing the filter certainly won't cause any harm - I think I changed the filter on each of my AW4s only the first time I changed the fluid - since I was digging in and inspecting everything anyhow. After that, it was drop, clean, reinstall. Easy enough.
 
I have two very old AW4's. I only dropped the pan on them once to change the filters and clean the pan, new gasket...and since then I just use the drain plug which drains a little under 3 quarts each time. And I add almost 3 quarts back in. I have had very good luck with just 3 quart transfusions, and some times, if needed a pint of Trans-X is added. One had a rear tail cone seal leak, and a shifting problem, that nearly stopped (down to maybe a pint a year now, if that) completely after 3 transfusions, and the shifting problem stopped after adding Trans-X with a transfusion, all over 20,000 miles ago.

If you shift from 1-2, to 3, get up to about 30-35 mph, then down shift manually to 1-2, the AW4 will shift into 2nd and stay there, until the Jeep speed hits about 8-10 MPH, then it will shift back to 1st. In 1-2, you need to hit about 4500 rpm for it to shift into 2nd, if the TPS is working properly!!!
 
Wow, thanks for all the info guys. That's tremendous, I really appreciate it!
 
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