904 LU trans problems

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Seriously. This stuff was recommended for my 2006 Sprinter. These vehicles were notorious for converter shudder from new in the lower RPM range. I was advised at the time that the shudder is more of an annoyance than a problem.
1785676094143.png
 
My understanding is that ATF+4 has some amount of friction modifiers, as do most modern ATF's.

The Instant Shudder Fixx above will show if TC lockup is the source. And it will indeed work very quickly.... like in less than a mile, you will notice a change. So it is a good diagnostic tool. There are longer life additives intended to last for many thousands of miles like this one which would be added if the Instant Shudder Fix helps: Highly Friction Modified ATF (HFM-ATF) Supplement with LXE® Technology

And BTW I have used these products the help reduce TC shudder in a Ford Taurus that had developed severe shudder issues. It helped and reduced the problem from severe to the 'sometimes annoying' level, but ultimately it would need a renewed VB and/or solenoid pack, or a new TC, to fully fix this particular car's issues.

But there are other sources of TC lock issues like wear in the valve body or other apply pressure mods, which I assume is what is being done with the suggested pressure adjustment. Also VB mod kits like have been suggested.
 
So Ive heard of Lubegard, but never used it.
The stuff Troy linked is 2 oz for $20 and the other Lubegard nm9 linked is 10 oz for $20? Cheap either way if its a fix.
Buy 1 of each?
CFD244 said:
Seriously. This stuff was recommended for my 2006 Sprinter. These vehicles were notorious for converter shudder from new in the lower RPM range. I was advised at the time that the shudder is more of an annoyance than a problem.
View attachment 1716571891
Click to expand...

nm9stheham said:
My understanding is that ATF+4 has some amount of friction modifiers, as do most modern ATF's.

The Instant Shudder Fixx above will show if TC lockup is the source. And it will indeed work very quickly.... like in less than a mile, you will notice a change. So it is a good diagnostic tool. There are longer life additives intended to last for many thousands of miles like this one which would be added if the Instant Shudder Fix helps: Highly Friction Modified ATF (HFM-ATF) Supplement with LXE® Technology

And BTW I have used these products the help reduce TC shudder in a Ford Taurus that had developed severe shudder issues. It helped and reduced the problem from severe to the 'sometimes annoying' level, but ultimately it would need a renewed VB and/or solenoid pack, or a new TC, to fully fix this particular car's issues.

But there are other sources of TC lock issues like wear in the valve body or other apply pressure mods, which I assume is what is being done with the suggested pressure adjustment. Also VB mod kits like have been suggested.
Click to expand...
 
LubeGuard recommends using the 2 oz Instant Shudder Fixx as a temporary additive and diagnostic tool to determine if the shudder is in the TC. It is not a long term additive. For long term treatment, then you use the other additive at the recommended dose per quart of trannie fluid.

If 'twer me:
- Do the drive tests to determine that this is TC shudder
- Do the pressure adjustments discussed earlier and re-test.
- If still there, then add the Instant Shudder Fixx and test to see if that improves things
- At this point if the Instant Shudder Fixx helps, decide if you want to try the longer term additive, or try the kits suggested, or change the TC. If you use the additive, AFAIK, it does no harm if it does not achieve anything.
- I have no knowledge on this particular trannie's hydraulics and tricks and wear points to be able to know if there are common problems in the VB that cause this. So sorry I can't help you there.....
 
I have the spring it takes to raise the lu speed for those early units that shuttered. Find out if it is shuttering at 25 to 35 under light throttle first.
 
Ok so got to spend some time, didnt do anything other than test drive(s), redo/adjust kd linkage, as well as shifter linkage. Also dropped fluid and all looks good, no flakes chunks etc.
I took a couple videos before the abv changes were made. 1 was 11 min long, not sure anyone wants to endure 11 min of me lol. Video I'll link is only a couple minutes long, done on same drive as 11 min one.
Not sure if much info is pertinent, hopefully lol.
Before adj 2-3 shift when floored was approx 55 mpg and 2500 rpm.
The next are just observations under steady speed.
25 mph 1200 rpm
30 mph (in 3rd) 1500 rpm
60 mph (3rd) 2800 rpm.
Heres short vid.


So after draining, adjusting heres readings
Shift points
1/2 10 mph
2/3 15 mph those were both under very moderate acceleration.
When floored the 2/3 shift is 55 mph
30 mph has kickdown, 35 and up does not.
Readings at steady speed
40 mph 2000 rpm
60 mph 2800 rpm
70 mph 3500 rpm.
Thanks all, hope that info makes sense.
 
Video is 1:45 not 11 minutes. Easy to view. Enjoyed the ride. Next time, we need some old-time country music LOL.

Useful narration. It sounds like you applied a lot of throttle when accelerating from almost a stop on the main highway around 0:48; is that correct?

What is the rear gear in this car? That 2-3 shift speed when floored seems low to me, but that depends on the gearing.

Some observations that might help:

At 0:48, when you accelerate from almost a dead stop, the first gear revving does not sound right. It is almost like it starts to rev and then the rev's stop rising for a moment. The revs certainly don't go up as far as I would expect.

At 1:06 another thing interesting happens: You going about 45 mph and then you push on the throttle: The engine revs rise for a moment and then drop back down. That is almost like the TC starts to unlock and then the trannie immediately re-locks it. Certainly not right....

Those 2 incidents make me wonder if the TC is locking almost immediately when the car starts moving or any throttle is applied. That would explain the lack of 'umph' in the car as that eliminates all the torque multiplication that you would normally get from the TC when accelerating, and maybe also the unexpected jumping of the car into gear when you got back home after the test drive last week. It might also explain the lack of kickdown, assuming the kickdown is dependent on the TC lock valve releasing first (which would make sense as you don't want gear changes with the TC locked).

But then again, it seems to upshift OK so IDK if that idea on the TC locking is right at all.
 
Maybe 20-30 minutes for 1st test drive. I did run on axles stands for over 1/2 hour total when 1st installed. Im thinking same thing with everything getting soaked thru and under load.
Thanks!
nm9stheham said:
How long was the 1st test drive? The new ATF+4 fluid may have now 'conditioned' the used TC lock clutches so that they engage smoothly.
Click to expand...
 
So I am bit confused.... but that is nothing new! I reviewed this whole thread, and also the prior thread. So is this a different trannie, with a lock-up TC, than the one that was being rebuilt in the prior thread?
 

Yes, i should've clarified this LU was a "spare". The orig 904 got rebuilt. I thought there was more LU info in that thread.
Do you happen to have 79 shift points? I have the 67 fsm, but thought with a LU the FSM shift points may vary. 323 gears btw.
Here's 67 fsm
nm9stheham said:
So I am bit confused.... but that is nothing new! I reviewed this whole thread, and also the prior thread. So is this a different trannie, with a lock-up TC, than the one that was being rebuilt in the prior thread?
Click to expand...

20260806_131555.jpg
 
Thank you.... things are making more sense now. So this later LU trannie is pretty much complete as you got it? And has no shift kit or other mods?

Those WOT 2-3 shift points are making more sense.
 
And it seems like the first order of business is to re-examine the whole throttle linkage to this trannie. That is one of the 2 things that determine the shift points.

I'll have to check with my son on his '65 Cuda but IIRC it was changed to the Lokar cable to make this work.
 
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