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Moses, time to pick your brain again on my 1994 dakota. I finally found the right extension housing, swapped it, filled the transmission, and now it has a severe vibration in first through 4th gears. i know i could probably just rebuild it, but when i got the extension housing, it came off a complete transmission i picked up, so im thinking of just using the used one i picked up, since its supposed to be a good transmission. The one odd thing i noticed though, with the transmission i picked up, is with it sitting on the floor in the garage, the shifter is very stiff, and i cant get it into any gear except first. Could that just be because it is sitting out of the truck on the floor in the garage, and because it has been cold out? I dont want to swap the transmission, only to find out i have issues with the one i picked up and have to take it back out.

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The extension housing in itself should not cause the vibration issue unless the countershaft or mainshaft bearing(s) slid out of position during the installation of the adapter housing.  Any growling or new noises from within the transmission?

 

Check out the step-by-step in my AX15 rebuild article, especially steps 181 onward in Part 2: http://www.4wdmechanix.com/Moses-Ludel-Rebuilds-the-Jeep-AX-15-Transmission,-Part-2-Assembly-and-Final-Work.html.  See if anything here resonates with the work you just completed on your Dakota's AX15.

 

Since the vibration is all with gears forward in the main transmission case, reviewing the AX15 article could help.  You know what you removed and installed.  Doesn't sound like the driveline, as you have a one-piece rear driveshaft, and it should connect to the transfer case readily with the slip coupler.  Look over the front and rear driveline mate-ups to the transfer case outputs, including the front CV-joint.

 

Also, there could be binding between the transmission and transfer case if this is not aligned properly.  Think through the steps you performed.

 

As for the unit on the garage floor, it can be difficult to shift a full-synchro transmission that is cold, especially without the gears rotating.  Old, cold gear oil never helps; however, AX15 lube should not be that heavy.  Before condemning the transmission on the garage floor, warm it up carefully with a space heater a bit, then rotate the input and output shafts while the transmission is in neutral.  Turn the input and output shafts in opposite directions to get gears and the mainshaft pilot bearing moving.  Once you get into each gear, rotate the input shaft.  Use reverse, too. 

 

Caution: Make sure nothing slides out of position if the adapter housing is removed!  The transmission shafts and bearings need to stay in position.

 

Review the AX15 article while the recent work you performed is fresh in your mind.  Since the adapter housing mates to the transfer case, consider the alignment issue.  I'm guessing that you did this work in the chassis and that you did not remove the transmission?  If you removed the transmission, is the crankshaft pilot bearing in position and in good condition?  A wobbling input shaft or sprung clutch hub, running out of center, can also cause the vibration you describe.

 

Moses

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One thing I forgot to mention. I drove it quite a bit while it was still leaking, and there were times I could tell by the whine that it was getting low on gear oil, so I think I may have hurt something in it. I did check out the other transmission very carefully today, and as long as it is somewhat warmed up and rotating, it shifts fairly easy, so I think I'm just going to swap the two. I just thought it was odd, since I have filled it several times before, that it now all of a sudden has the vibration in it. I also neglected to mention that for the most part, knowing it leaked, I was very careful not to push it too hard, staying right around 55 on the highway, no fast starts or letting the clutch out hard, but the day before the vibration started, I was running very late, and in trying to get where I needed to be on time, I pushed it pretty hard, doing 65-70 on the highway for about 45 miles, and the vibration started the next day, so that may have had something to do with it. Im also pretty sure the issue is strictly with the transmission, because in 3rd or 4th, it vibrates hard enough that the truck shakes, but once I push the clutch in and let it coast, even at 50-55, the vibration instantly stops.

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I did do the work without taking the transmission out of the truck, so I doubt it is clutch related, and there isn't any noise at all out of it, new or old, as long as it is filled with gear oil. I also doubt it is a transfer case issue, because I had to put it in 4HI a couple days ago, and it engaged and disengaged without any issues. I was pretty much leaning towards swapping the old one with the used one I picked up, but I didn't want to do all that work if you thought there may be something wrong with the used one, but now that I know it shifts fine, it looks like that is what I am going to be doing.

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Biggman100...Too bad that you're doing the transfer case removal again, but it sounds like the oil-starved AX15 scorched the count shaft and upper bearings.  These are close-tolerance gear systems in the AX15, and they have zero tolerance for running low on oil.  Aside from actually starving the bearings, the shafts and thrusts can get hot and lose hardening. 

 

In this situation, the counter gear has now crept away from the main shaft due to bearing damage and run-out.  You'll be ahead with the other transmission if in "good used" condition.  Sometime (like we have time?), you might tear down this damaged transmission to confirm the damage.  I have a good idea what it looks like without taking it that far: scorched bearings, gear scoring and a lot of metal debris in the bottom of the case.  Some parts might be salvageable.

 

Let us know the outcome...

 

Moses

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  • 2 weeks later...
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Biggman100...Here are illustrations of each for your identification.  The Dakotas apparently all use the AX15.  Jeep 2.5L four-cylinder models use the AX5.  Here is the difference: 

 

1994 AX5 Transmission.bmp 1994 AX15 Transmission.bmp

 

This should help.  Your Dodge Dakota trucks are V-6s, so the AX15 is the transmission you need...

 

Moses

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Incidentally, I looked up the official oil recommended by Jeep for the 1994 Cherokee and Wrangler YJ.  The factory shop manual calls for API 75W-90 GL-5 of good quality.  No distinction around conventional versus synthetic, consumers were on their own here.  "Good quality" does provide a "good conscience" if you elect to use conventional GL-5 75W-90 lube and a quality brand.

 

As for filling, Jeep suggests just to the fill hole when cold.  (Might spill out slightly when checked warm.)  A clean and completely empty transmission should take 3.27 quarts in your 4WD version of the AX15.  A used transmission, drained but not flushed thoroughly?  I'd guess 3 quarts or under would do it.  In any case, fill to the base of the fill hole on level ground and cold...Don't overfill.

 

Moses

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Want more thoughts about the AX15 gear lube?  This includes the "brass synchro ring versus sulfur discussion" and other points we haven't gotten to here.  The exchange is at our Jeep forum, right here at this address: http://forums.4wdmechanix.com/topic/47-ax15-transmission-gear-oil/.  Take a peek, it's a nice read!  The synthetic Redline bias gets aired, too...

 

Moses

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  • 2 weeks later...

Moses, new update on this. I didnt have time to swap the transmission, due to having to get some stuff done, so i tried another approach. I drained the gl-5 80w-90 i had in it, and replaced it with pennzoil syncromesh, and now the vibration is gone, but shifting into 4th is at times a real chore. Normally what i have to do is when i shift from 3rd to 4th, i have to pretty much force it into 4th, or it grinds and kicks back out, but once it is engaged in fourth, i can drive for miles with no issues, but, to downshift from 5 to 4th, i have to put it in 3rd, keep my foot on the clutch, and pretty much ram it in 4th. I even drove a 480- mile round trip, half of which was towing a car on a tow dolly up some pretty big hills with it doing that, and other than that one issue, it shifted fine, and didnt vibrate at all, in any gear. At least now i know to pay more attention to what fluids i use in the dakota transmissions, because as i learned the hard way with my automatic 1991, using the wrong fluid can have disatrous consequences. I used Dex/Merc instead of ATF+4 in that truck, and burnt the transmission up a week later.

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  • 2 months later...

Moses, i finally got the time to tear down the old transmission from my truck, and although i didnt find much in the way of metal in the bottom of the case, i did find that 2 of the brass synchros were broke, one in 3 pieces, and a couple of the gears in it had the teeth severely wore down in spots, but it wasnt uniform in how they wore down. The gears may have been like that before i swapped the extension housing, and since i drained all the fluid out of it for that swap, that may be why i didnt find much metal in the case when i tore it apart today. Either way, im going to put the extension housing back on the other transmission i have, and once im done replacing all the gaskets and cleaning up the engine, i am going to put it back in the truck, but, first i have a question i never considered to ask before now. Is there a gasket between the extension housing and the transmission, or did chrysler just use silicone between the two? I looked through your rebuild, and i may have missed it, but i dont remember you mentioning it when you put the extension housing back on.

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One last question about this. I looked on 4wd hardware's site, and all they show are parts for the Jeep AX15. All i am after is the gasket for the shifter housing, and the front and rear seal for the transmission case, so would those parts be the same for the Jeep and the Dakota?

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Biggman100...Go to my AX-15 rebuild article, see illus. AX-15-179 to AX-15-186 at: http://www.4wdmechanix.com/Moses-Ludel-Rebuilds-the-Jeep-AX-15-Transmission,-Part-2-Assembly-and-Final-Work.html.  The extension housing uses sealant as shown.  Mopar recommends Threebond® Liquid Gasket P/N 83504038 (if still available).  This is a 1998 shop manual reference.  I used sealant sold through 4WD Hardware for this work.

 

My rebuild is a Jeep version of the AX15.  Compare this with your Dakota seals.  It's unlikely that Jeep and Dakota versions of the AX15 would differ.  If you need seal part numbers, describe the Dakota year and equipment.  I can furnish OE Mopar numbers for the seals in question.

 

Moses

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