Quick question, Just need more opinions

[Stitch6719]

Hey guys, haven't posted in a long time. Had a lot going on with college, moving, and working on my new house. Anyways I have noticed that my 85 bronco II auto 4X4 isn't pulling as hard anymore. It's shifting fine, down shifts into passing gear fine, but when it does the RPMs go up transmission down shifts but no added pull or power. I'm fairly certain that its my torque converter going, but I wanted a second opinion. Will draining and refilling the trans and converter maybe fix this issue or do I just need to swap the converter? also whats a quick way to tell which auto trans I have? I'm trying to find a manual to swap my auto with, but haven't had any luck yet. I'm even looking for one that needs rebuilt, not the first time I have rebuilt a manual.

Thanks

 

[ab_slack]

I am not certain the problem is the transmission.

Of course when it down shifts the RPMs increase (lower gear and all that).

Now if you are saying when it down shifts suddenly it feels like the engine is decoupled from the drive wheels then that may be a trans.

For testing purposes, manually shift to the lower gear so change in engine RPM from shifting isn't confused with change due to torque converter allowing slip.. Also with an auto trans there is usually a point at lower RPM/Idle or while otherwise coasting where engine RPMs can drop independent of wheel speed (sort of like coasting on a bicycle you don't have to pedal) While trying to accelerate though, be it lightly to strongly the engine RPMs should not change without wheel speed also changing. If RPM under that circumstance changes lots and wheel speed isn't then yes torque converter would seem to be letting it slip.

If it isn't doing that though, then it comes to engine power. A lower gear usually moves engine to higher RPM where it can provide more power (thus more energy to move) and the gearing turns that to torque providing more push. If that is not making a difference and torque converter isn't slipping and letting engine RPM increase then you just aren't getting engine power.

There can be numerous reasons for engine power not being good at higher RPM from fuel problems, are intake problems, spark advance problems, thru exhaust problems (clogged cats)



Can't answer your question about fluid. Low fluid can result in slip. If not low, I do not know if changing fluid would resolve it.

 

[Stitch6719]

I am getting high RPMS and not enough speed gain so I do feel that its the torque converter letting to much slip. Is there a way to easily identify which transmission I have? As for the engine, I am getting ready to rebuilt my carb, and figure out how to remove the smog control and pump, is there a tech page for that here?

 

[ab_slack]

Odds are it is an AL4D, but look here:

http://www.therangerstation.com/tech_library/AutoTrans.html

I know yours isn't a manual, but for anyone wanting to identify a manual trans look here:

http://www.therangerstation.com/tech_library/ManualTransmission.html

 

[Stitch6719]

Found out late yesterday that it is an A4LD. so now I'm probably gonna shop around for a torque converter. go enough yards around me that I'm sure I can find one fairly easy enough. Hey just a thought, but could the solenoid be bad? I'm not sure what it means about it controlling converter lock up, just weighing all my options here.

 

[ab_slack]

In your original post you spoke about when it down shifts and passing gear where this problem occurs.

Does it accelerate okay from a stop?

I would expect torque converter issues to occur under both conditions so maybe it is just the way you wrote it that makes me think other than torque converter every time I read it.

If you haven't seen this it may be helpful

http://etereman.com/blog/ford-transmission-2/common-problems-with-the-ford-a4ld-transmission-that-all-shop-owners-should-be-aware-of

It mentions old fluid can cause slip.

Torque converter lockup solenoid turns on/off direct coupling thru the torque converter. This typically only engages when cruising at a fixed speed and when this engages all squishiness between engine and wheel speed goes away, wheels change in proportion to engine speed for that gear. This is largely a fuel economy measure although it can keep trans fluid cooler.

Typically when you go to accelerate heavily and transmission shifts it first unlocks resulting in some higher RPMs and then downshifts. It tends to remain unlocked until acceleration is done and you go back to cruising.

 

[Stitch6719]

Yes it takes off smooth from a stop and accelerates fine through the gears. The only time I notice and acceleration/power loss is when I step on it and it down shifts into passing gear. that is when I get high RPM's the trans down shifts fine, but no increase in acceleration. Fluid and filter change is next on my list. I have one week left in this semester and I will be doing a carb rebuild, and trans fluid/filter change. I plan on swapping to a manual before to long which is why I don't want to sink a bunch of money into my A4LD, even though I am going to rebuild it and sell it later down the line. I see a lot of topics on trans swap. Which is best for a 2.8 4X4 (i'll eventually have a slightly modded engine) the FM146 or M5OD. I have a M5OD in my 89 f-150 XLT Lariat and loved it, but that was also a 302 4X4

 

[ab_slack]

So the torque converter is working fine at low RPM and accelerates okay at low RPM.

So when at high RPM and it down shifts, does it feel like the engine is disconnected from the trans? Engine will RPM will of course go up with the down shift, but after it downshifts what happens other than not accelerating? Does it start going slower? Does the engine go up to redline?

At what speed is the downshift occurring and what engine RPM when it is not accelerating?

I am trying to understand why this is a torque converter problem and not a high RPM power problem.

 

[Stitch6719]

So the torque converter is working fine at low RPM and accelerates okay at low RPM.

So when at high RPM and it down shifts, does it feel like the engine is disconnected from the trans? Engine will RPM will of course go up with the down shift, but after it downshifts what happens other than not accelerating? Does it start going slower? Does the engine go up to redline?

At what speed is the downshift occurring and what engine RPM when it is not accelerating?

I am trying to understand why this is a torque converter problem and not a high RPM power problem.

I'm not saying that it is definitely a torque converter problem, and am very much open to options that are alot cheaper. Yes it feels like the engine is disconnected from the trans, It doesn't slowdown, but holds the same speed with slight increase in acceleration. the downshift is whenever i put the pedal on the floor, the trans downshifts, rpms increase, the engine does not redline, but I dont have the acceleration I should have. I adjusted the bands yesterday and it's running better but still not what it should be. I am going to do a fluid and filter service, as well as rebuild carb next weekend after finals