AW4 doesn't start when cold

[sacem]

I have a problem that arises everytime the weather is mildly cold (50ºF) the AW4 trans in my 90XJ 4.0 L with 2" raise, 31x10.5 tires Limited slip up front, stock motor, trans and diffs.

The car will not move for several seconds specially in Reverse, in Drive it will crawl but without much energy (will not go up a garage ramp) until it seems like it fills up and then suddenly it will kick in even with a tire screetch (specially in Reverse).

The problem can get much bigger if the tem goes to the 40's as then it will simply not move in reverse (I have to get out of the XJ and push it to get it out of the parking lot) and shifting to Drive will start things moving, at those occasions i will have to drive several miles before the Reverse will work.

Also when its cold the AW4 will not upshift when driven unless it is flooring it and going up to 3,000 + rpm's then it will shift when I lift the foot from the gas after 2 or 3 bursts like those it will normalize.

The trans up and down shifts normally, kicks in very nicely on the highways, downshifts with no problem in the city and the rest of the time simply works perfectly.

Can anybody give me some clues about the reason for this.

SACEM

 

[john mitchell]

need just a little more info:

Will it operate normally when it is warm. What about stopping when hot then restarting when partly cooled, like when you go to the store for 10 min, will it operate normally then?

How many miles on it?

Fluid level check?

Preliminary diagnosis sounds like a lack of fluid getting to the pump, check the fluid level when warm idle in park, and the jeep is level. The best place is the concrete pad at a gas station.

or the low gear clutch assembly is not engaging properly, there are many reasons for this problem from bad linkage to blocked passage to worn clutches. 31" tires with stock gears is hard on the trans but the AW4 is a good tranny, do you tow with it?

Yer in good hands here.

 

[Comanchedude]

I agree with the last post
what have you done
have you checked fluid level and have you changed the filter and fluid?
it does sound like low fluid or maby bad pump pressure that could be from worn seals and maby a fluid change would help?

 

[sacem]

Thanks guys:

mi 90 XJ has 230,000 mi on it but is 45,000 mi from a complet engine rebuild new pistons, new main, rod and cam bearings, valves, pump, etc. Trans never been touched except for filter changes.

When I stop it for 10 to 40 min it will start perfectly with no hesitation even in Reverse (the worst situation).

The fluid level has been checked with the XJ completly level, cold AND hot after driving for minutes and for hours (done last month 2,000 mi tour around the southern mountains and climbed 5 times over 14,000 ft of altitude no problem with the trans except when stopped for long periods).

The last fluid change was done with the filter change which forces you to drop the bottom pan of the trans. That was about 15,000 mi ago.

Thanks for the help

SACEM

 

[Quarterwave]

I'd try doing a FULL trans flush and replacing with new Dexron III. I had some issues with my trans a while back, where it would jump out of gear after driving about 100 feet - likewise for going around a corner while the trans was still warming up. I checked the fluid levels at the time and all was well. But after getting the trans flushed, the problem went away, and the gearbox shifted and felt so much more "solid". Now, I try and make a point of changing out my fluid about every 10k miles.

Best of luck with it.

 

[mgreen84]

The filter will sometime clog with a "gel-like" crud if you use bad or cheap fluid and once it gets warm and melts out of the filter it runs fine. I didn't believe it, until we had one come into the shop and the filter looked like it was full of red jello... this happens when cheap fluid gets wroked hard and breaks down... what brand of fluid did you use?

 

[sacem]

The filter will sometime clog with a "gel-like" crud if you use bad or cheap fluid and once it gets warm and melts out of the filter it runs fine. I didn't believe it, until we had one come into the shop and the filter looked like it was full of red jello... this happens when cheap fluid gets wroked hard and breaks down... what brand of fluid did you use?

The fluid was provided at the same shop that changed the filter, but looking back they have been also replenishing any fluid that has been added for a long time and I don`t have the slightest idea of what they are using.

I will pull the cover, rechange the filter and use that Dexron III fluid that has been recomended, hope I can find it around here.

To johnmitchell: I forgot to answer about the worn disk situation: I do not think it is the problem as I have been able to pull out from the sand a stranded Toyota HiLux with no effort at all so power transmission, once it is warm is not a problem.

I do not do towing frequently, just my Yamaha Wave Venture on a trayler but that I can move around by myself at the beach or my VW powered sand buggy rail, but that's done once or twice each summer from the city to the beach where it stays for the whole summer and then back, in any case the XJ only reflects the towing in the lower gas mileage.

I think I will try the filter and ATF change first.

Is there a way to FLUSH the entire system after draining the fluid with something that will clean it (with out destroying the O-rings and so on) and then refilling with new fluid?

Thanks

SACEM

 

[Quarterwave]

As far as I'm aware, there are two lines that enter the trans - 1 sending and 1 return. If you undo the return line and start the engine, the trans pump will engage and pump out the contents of the trans, cooler and lines. IMHO, it's definately worth doing this, as it gets rid of all the old fluid that's in the lines and cooler which saves contaminating the new fluid with all the old stuff. If you do a search on that topic, I'm sure you'll find a detailed write up about it - I've read some posts before on this forum for the exact procedure.

Good luck.

 

[sacem]

Thks for the tip, it looks very simple and it should be, I'll be doing that soon

Regards

SACEM

 

[Cherokee91Red]

Just checkin, but did you make sure to use the same fluid when you did the fluid change? If you used a Chrysler ATF mixed with the 2-3 quarts of Dexron that stay in, unless fully flushed that could cause some problems. I did that stupidly the first time I changed out my fluid and it had trouble shifting until i replaced the fluid with all Dexron.

 

[sacem]

Just checkin, but did you make sure to use the same fluid when you did the fluid change? If you used a Chrysler ATF mixed with the 2-3 quarts of Dexron that stay in, unless fully flushed that could cause some problems. I did that stupidly the first time I changed out my fluid and it had trouble shifting until i replaced the fluid with all Dexron.

I really do not know even the brand of ATF that the car service shop has used and probably, as it is usual around here, it must have been the cheapest fluid around.

To flush every part throuly, I'm planning on doing the following:

1) Disconect the line from trans pump to radiator and pump out and discard all the fluid I can out from the trans.

2) Open the bottom cover of the trans, drain any rest of fluid, replace the filter, wipe as much as I can around there.

3) Reconect the line to the radiator, close the trans cover and fill with fluid, start the engine, fill the trans to operating level by dipstick marks.

4) Take the XJ for a drive so that the trans warms and makes any deposits more likely to be removed by the clean fluid.

5) Stop the engine and without letting thge trans to cool, disconect again the line to the rad and drain as much fluid as I can.

6) Reconnect the line to the rad, refill with new fluid and I HOPE this has cleaned the trans.

If any one sees something that I'm missing please let me know.

BTW I have not searched for the Dexron III that has been recommended to me but I don't think it is going to be availiable around here.

I'll check and keep you posted

Thanks

SACEM

 

[4xBob]

Good plan, but a change in order is needed. If you pull the pan/check the filter/clean the pan/reinstall then refill the pan BEFORE you disconnect the return line, then the pump will have a pan full of clean fluid to use to push out the old stuff. When the clean Dexron starts coming out, it is a brighter red, and you can see it. This is what I do. I take out (from the return line) 2 litres (quarts), stop the engine and refill, then repeat until done. I don't want hydraulic lines and torque converter with air in them, so I don't try and pump out more than that before adding more to the pan. I timed it, about 12 seconds running to pump out 2 l (or quarts- close enough) on mine.

 

[jeepsrock]

I think all this may be somewhat caused by the tranny having the wrong fluid (probably has atf +2 or +3) ...i would drain/ flush using a box and a half of mercon/dexron 3 stuff.

pete

 

[JoBo]

I think all this may be somewhat caused by the tranny having the wrong fluid (probably has atf +2 or +3) ...i would drain/ flush using a box and a half of mercon/dexron 3 stuff.

pete

Exactly. When trying to get fluid for the first change on my 96, several places recommended the WRONG Chrysler fluid. I don't know where you live but Dexron III is by far the most common fluid there is. At least in the US.

JoBo

Edit: I now see you don't live in the US but it still should be available there.

 

[sacem]

I'm starting to pull the pan out from the AW4 and beginning to follow all your instructions, let´s all hope that that is the solution as I'm starting again this weekend up the andes to 15,000+ ft mountain passes.

SACEM1

 

[sacem]

I found DEXRON III/MERCON on several brands around here (Lima-Peru) I had never checked before but I found it in Castrol, Penzoil and Texaco I bought a 5 gallon pail of Texaco so that I can do all the flushing and changing with no problem.

BTW can any body give me how many quarts go into the AW4, I know it has been posted before but I can't find the data.

Thanks

SACEM1

 

[jeepsrock]

I would drain it the first time by pulling the pan , change the gasket and filter and then drive it for 5-10 min then empty it the second time by just pulling thte screw and refill. By doing this you guarantee your get as much of it as you can.

pete

 

[sacem]

I already pulled the pan off, but did not found too much gunk in the pan, have to get the filter out but its already dark and I'll continue tomorrow.

The idea of driving it around for some minutes had also come to my mind and I think I'll just do that

Thanks

SACEM1

 

[jeepsrock]

dont forget to fill before you drive it..
pete

 

[sacem]

You bet

Thanks