AW4 slipping 16k miles after rebuild.

So yeah background...1990 4.0 AW4. I had the tranny rebuilt 16,000 miles/year and a half ago. Two weeks ago I was getting up to speed on the freeway and it slipped bad. I pulled over and let it idle for a second and started to go again, it drove fine for two weeks. Fast forward to tonight. I was accelerating up to 35mph, once I hit about 25 I noticed that the speedometer wasn't moving but the tach sure as hell was. I pulled over once again let it idle for a few and started to move again, it was fine. I'm not sure if the RENIX TPSs can play tricks on the tranny like the HO ones? Could that be my problem? I have a 4 month old Borg-Warner one on there right now and I'm pretty sure it's still adjusted, although I will check that tomorrow. I checked the fluid and its a very light brown color, but it doesn't look bad, and it's not leaking at all. The only thing I can think of that might play a role in this is that I put a new radiator in about 3 weeks ago. However, it had the hookups for the tranny cooler lines so doesn't that mean that there is one in there? I connected the lines the exact way they were connected to my original one. Is it possible that the lines in the tranny cooler could be clogged? Does anyone have any ideas on this, because I am stumped and frustrated.
Thanks guys,
Collin

Many people are of the opinion that rebuilding an AW4 is a foolish choice. It is more cost effective to get a used factory tranny since they are so reliable.

I don't know what the problem is with yours, but rebuilding the AW4 is pretty rare, there is the very real possibility that the shop that did it screwed up.

I hope that AAMCO did not do it... i would get a junkyard lower mile tranny.. the aw4 is the most bulletproof machine ever

BrettM said:

Many people are of the opinion that rebuilding an AW4 is a foolish choice. It is more cost effective to get a used factory tranny since they are so reliable.

I don't know what the problem is with yours, but rebuilding the AW4 is pretty rare, there is the very real possibility that the shop that did it screwed up.

Click to expand...

Hey Brett I know you know a lot about the AW4, I've been reading some of your old posts. Which years would fit in my 90, this is what I've gathered so correct me if I'm wrong.
87-90 - Direct swap
91-96 - only have to deal with the spline count issue.
97+ - have to deal with spline count and electronic issues. Could you elaborate at all on the 97+ electronic issues? I know in one of your old posts you said something about a speed sensor, and the connector at the TCU are different right? Thanks again for the help.

wilcharl said:

I hope that AAMCO did not do it... i would get a junkyard lower mile tranny.. the aw4 is the most bulletproof machine ever

Click to expand...

No although a month before the first time it crapped out AAMCO did do a fluid/filter change to it which probably wasn't brilliant.

Check the TV cable for proper adj and operation, it acts a pressure regulator also.

If your fluid is 'light brown', you need to change it. Sounds like your tranny is having some overheating issues.

Click to expand...

And that would also point to the radiator.

just curious who did the rebuild on the AW-4 id be wanting some money back unless it was a buddy

I had an AW4 rebuilt.

It lasted about 15K.

I found an AW4 w/ 60K miles on it, and haven't had a problem since.

AW4s don't take well to a rebuild.

If your fluid is 'light brown', you need to change it. Sounds like your tranny is having some overheating issues.

wilcharl said:

just curious who did the rebuild on the AW-4 id be wanting some money back unless it was a buddy

Click to expand...

I had a place in town do it. They put a 12k/12 month warranty on it. It's been 16k/and about 18 months. If it was still under the time period I'd roll back the odometer because I really don't think it's right that a rebuild that I paid $1500 is trashed after a year and a half.

BigBlackHeep said:

Hey Brett I know you know a lot about the AW4, I've been reading some of your old posts. Which years would fit in my 90, this is what I've gathered so correct me if I'm wrong.
87-90 - Direct swap
91-96 - only have to deal with the spline count issue.
97+ - have to deal with spline count and electronic issues. Could you elaborate at all on the 97+ electronic issues? I know in one of your old posts you said something about a speed sensor, and the connector at the TCU are different right? Thanks again for the help.


No although a month before the first time it crapped out AAMCO did do a fluid/filter change to it which probably wasn't brilliant.

Click to expand...

Try changing the fluid again, this time with good quality fluid. I doubt AAMCO used anything high quality and possibly the wrong fluid.

97+ added a front input shaft speed sensor. The rear sensor changed as well, sending 4 pulses per rev instead or 1. So you would need to keep the 97+ TCU with the tranny (or go the harder route and built an adapter box like I did). The TCU between 90->91 changed a little for the ODBI versus Renix but it's mostly the diagnostic lines which don't matter on the Renix.

lawsoncl said:

Try changing the fluid again, this time with good quality fluid. I doubt AAMCO used anything high quality and possibly the wrong fluid.

97+ added a front input shaft speed sensor. The rear sensor changed as well, sending 4 pulses per rev instead or 1. So you would need to keep the 97+ TCU with the tranny (or go the harder route and built an adapter box like I did). The TCU between 90->91 changed a little for the ODBI versus Renix but it's mostly the diagnostic lines which don't matter on the Renix.

Click to expand...

Well yeah its not AAMCO's fluid anymore since it was rebuilt after they did the fluid change. Will the plug be the same on the 91+ as the 90- or no? Thanks for the help. By the way to everyone who read my original post, I checked my tranny cooler and the fluid is flowing through it just fine, I thought it might have been clogged but it's not.

BigBlackHeep said:

Will the plug be the same on the 91+ as the 90- or no?

Click to expand...

The wiring harness connectors at the tranny and the trans computer are the same for the Renix and ODBI (up to 96) setups. The differences between the years are where some of the wires go under the hood. In the ODBI setup, the diagnostic wires and the tps sense wires go to the engine computer. The Renix setup has the diagnostic wires going to the yellow diagnotic connector under the hood and the tps sense wires go to the second output on the tps sensor. The NSS is identical as well. On 97+ the connectors changed on the tranny and the NSS, but the wire colors are the same.

Oh, aside from the output shaft spline count change, I believe starting with the HO engine, the 4th gear ratio changed from 0.79 to 0.75. The changeover might have been later. Using an earlier TCU with the older tranny or vice-versus will have a minor affect on the 4->3rd downshift point. The few hundred rpm difference in the downshift point isn't noticeable (I have an earlier tcu with a later tranny).

Well today the AW4 slipped again. This time it would not get out of 2nd gear. I drove around like this for about a mile at real slow speeds and then I had the idea to pop it down into 3. After this it shifted fine again, so I threw it back in Drive. I drove it another 15 miles some on freeway and some not and its been fine the rest of the night. The only thing I can think of is the not getting out of 2nd sounds like a solenoid, but why would throwing it into 3 cure that? It seems to drive fine still, but I've noticed ever since the first time it happened my acceleration hasn't been as good. Could this be because the fluid is brown or because the filter is clogged? Any ideas at all would be appreciated, I just can't afford to drop another $1500 right now.
Thanks
-Collin

Because the Range switch is not making good contact in third.

langer1 said:

Because the Range switch is not making good contact in third.

Click to expand...

Can you elaborate on this a little bit langer? Would this be what was causing my other problems ya think?

Ok, I've been reading up on it a little bit, is the range selector switch internal or external to the tranny?