Remember my "Transmission slipping at 3,300-3,400 RPM" post?

[studio460]

Hopefully, some of you may remember my "transmission is 'slipping' at 3,300-3,400 RPM" post which I wrote shortly after I purchased my '03 Marauder 300B way back in March of 2003. Many of you responded that (and I'm paraphrasing here) the stock transmission programming often "hunted" for gears and that the Reinhart chip would resolve the general problems associated with the poor shift-point programming. I think Sarge also mentioned some related issue with the stock torque converter, I can't quite recall.

Well, I recently had a FordChip dynotune performed on my Marauder by Jerry, and the car does shift MUCH nicer now. However, I was able to repeat the following condition over and over again this evening as I was doing some more studied test driving of the car:

1. While driving at a moderate speed, with RPMs at about, say, 1,500 RPM (this part is arbitrary), manually shift the transmission into second gear.
2. Depress the accelerator and hold at anywhere between 50%-100% throttle.
3. As the tach reaches approximately 3,300 RPM, the engine RPMs FREEZE at 3,300 for approximately 0.5 seconds.
4. After this visible and tactile delay, the tachometer/engine RPMs increase normally.

I can repeat this over and over. This is a repeat of the same "transmission" anomaly I had reported before. For all of you who have Reinhart chips and/or FordChip dynotuning already, have any of you ever experienced this? If you haven't, would you mind trying this test the next time you're out? Any feedback on this issue would be most welcome. Any possible diagnosis, absolutely welcome. By the way, when I took it to the dealer nearly six months ago regarding this problem, the service writer reported, "That's the way it's supposed to be." This is also the same car that had its transmission temperature sensor fail during the first 24 hours of ownership (but wasn't taken to be repaired for several weeks). Thanks again for any input on this issue.

[SergntMac]

I don't know if any of this will help you Shooter, let's throw it out there and see what flies?

The "gear hunting" is a trait of a bone stock MM, and it does get fixed with a dyno tune because line pressures are adjusted for better shifting. I'm not sure this is is related to what you describe as a "plateau" in RPMs. Symptom or not, many here have noted poor shifting, and addressed that with the same fix.

What you describe I see on my MM at 5000 RPM with regularity. I have seen it on other MMs between 4000 and 5000 RPM. The RPMs plateau briefly, and go on. Yes, it is repeatable, and one source of advice says it's visible on my dyno report as a small blip, yet I could not agree with that. But, it's there, I can see the tach freeze for a moment.

OTOH, this brief plateau does not seem to affect performance, because the car continues to build power and speed. I have no better explanation to offer, other than to wonder about the quality of our OEM tachs.

Open for suggestions...

[MMM2003]

I can verify Shooters finding. I have the identical situation on my bone stock MM. I did a search on this before, and found some mentioning of the fuel pump/fuel pressure problems. Not sure what ever happened to that thread, but apparently we are no the only one's. Do a search for SM# 16941 and see if you can get some info out of that.

Good luck.

[SheboyganGuy]

Mine did this before the dyno-tune. I always felt it in 2nd gear around 3200 rpm. I haven't noticed it since I had the Fordchip.com treatment. Will have to check this out later (I'd do it now, but I have the truck at work today...). Will report back this evening!

[uwsacf]

My new CV does this during 2nd/3rd shift.......

sorta stalls for a second - sounds sorta like clutches slipping then goes into gear....

I'm figuring the trans won't make it thru the warranty period...

[Warpath]

Here's my uneducated guesses:

1. The 0.5 sec delay allows the T/C to lock up. I think Lidio posted something about the T/C locking up in all or most gears. I remember something in his post about allowing the T/C to lock up. Look for his post in a broken tranny thread.
2. This triggers something in my mind about Mustang/Cobras. I think some people have mentioned a plateau on curves before. For the life of me, I can't remember their speculations. It may still be there at <50% throttle and you just can't feel it.

[Zack]

What do you think Curious George?

[TripleTransAm]

Could that hesitation be the torque management kicking in during the 2-3 upshift? I think I've experienced what's been described, and I'm fairly sure it wasn't the TCC engaging as I previously thought. Most definitely coincides with what should be the 2-3 upshift.

Perhaps those of you with dyno tunes or chips have had the torque management reduced or modified and hence it's not as noticeable anymore? (and thereby replaced with a firmer shift?)

[studio460]

Thanks for everyone's replies. I really appreciate all of your comments!

1. The engine is definitely "holding" that RPM--the engine "pitch" is the same and there is no acceleration. The tach is not the problem.

2. Thanks to those of you that reported similar symptoms. That leads me to believe that this is in fact a normal anomaly of our drivetrain.

3. The hesitation is smack dab in the middle of the RPM run in the gear. I am accelerating from low RPMs straight through 3,400 RPM all the way to 5,000-6,000 RPM in the same gear.

4. I am guessing that it's not the transmission. That it's an anomaly of our stock torque converter doing "something." But I don't know. I'm not a mechanic. I don't know a whole lot about cars. I just know its repeatable and sorta weird.

[studio460]

I went back and read the responses to my original thread posted nearly six months ago . . . I believe Cyled (and probably others as well) had already posted what seems to be a highly plausible answer:

"What you are feeling is what Mercury advertises as "A High Stall Torque Converter". Designed to help deliver the power without burning up the tires, plus (IMHO as well as some others on the board) to keep from tearing up the drive line on a 4100 lb car. The idea is to be able to take off from a stop light with out just smoking the tires. Between the torque converter and the beefer tires, it helps get you traction (a plus for winter driving). So the car waits to 3500 rpm before letting full power to the rear wheels (when the converter is locked out), hence the feeling of slipping.

If you do a search for torque converter you will fine a lot of good information. A few owners have switched out for smaller converters which has given proven good results. Also, chips like the one from Dennis, will lock out the torque converter on wide open throttle so you will not feel this." --originally posted by Cyled

Thanks, Cyled!

[schuvwj]

I was wondering if some has a Trany parts list needed to fix our tranys right, so we could order a list parts and replace them before they fail. Mac sent me some pics but no numbers?

Thanks!

[looking97233]

I don't know if this will help....
I have a Bronco with a little 460, makes big torque. It has a C-6 trans.(no lock-up TC) stall is about 2800. When driving spirited(WOT) the tach. climbs to 2800 or so, then stops for about 0.5-1.0 sec. Although the tach stops, the spedo. continues to climb quickly. I think that this is the converter slowing?(going from the 1.98:1 to close to 1:1) as engine torque builds and can push the higher ratio. I actualy think this is the time that my Bronco acclerates the quickest as the spedo really climbs as the tach. is pretty much stopped.I don't think I explained that too well, so if anybody can do a better job please do. Or if somebody knows and I'm totally wrong please correct me.
BTW My MM does the same thing as everybody elses too.
Also, the Bronco beats up on Mustangs and may be quicker than my Stock MM.

[TripleTransAm]

Originally posted by looking97233
It has a C-6 trans.(no lock-up TC) stall is about 2800. When driving spirited(WOT) the tach. climbs to 2800 or so, then stops for about 0.5-1.0 sec. Although the tach stops, the spedo. continues to climb quickly.


Yup, that's exactly the behavior of the torque converter, allowing your engine RPM to flash to a higher RPM where (supposedly) your engine will be making its best power for launch. And the added benefit of the torque converter is that while all that slipping is going on, you're getting some torque multiplication going on as well. Once the tranny speed (directly related to road speed via the gearing ratio) gets up to more or less the engine RPM, then both begin to climb together, as you saw.

Not many V8s out there coming out of the factory with high-stall converters, and this brings on different behavior that can throw us off since we're not used to it. On my GTA, the tight torque converter means the engine is usually beyond its 1600-1800 RPM stall speed by the time upshifts occur, whereas I've noticed on the MM that in MANY conditions an upshift can occur while the engine is still below the stall speed. This makes for weird hesitations that are actually upshifts, yet the engine RPM hardly moves down after the upshift!

With the engine cold, this is very noticeable since the TCC doesn't engage when the engine is cold. I've noticed that when I accelerate such that the engine is holding steady at 2500 or so, you can pick off the 1-2 and 2-3 shifts easier since there is no TCC to distract you. But it is disconcerting because the engine RPM doesn't change much if at all, since I'm below the stall speed of the converter.

Once I scrounge up the cash, I should be able to prove this is the case via autotap. NBC, I believe I once mentioned in your earlier thread that I thought it was the torque converter kicking in... based on the previous paragraph I would have to retract that and say that it's the factory's too-early 2-3 upshift that you're experiencing. But I'll have another look at it tomorrow when the engine's cool. I might even videotape it, just to be able to compare with what you're experiencing.

[Mongoose]

For all of you who have Reinhart chips

NBC Shooter,
My MM had the same symptoms.
Just had a Reinhart chip put in Friday. Dennis also changed the tranny fluid and put in some CRC posi-trac additive with the new fluid and a set of DENSO plugs. What a difference!!!!:D No more hesitation under normal acceleration. Under WOT, the same ( no hesitation) but with a firm shift.:burnout:
Lovin' it.

[studio460]

Well thanks for all your input on this rather tired post. After becoming more familiar with my shifting/acceleration patterns, I'm pretty sold on the idea that this "hesitation" is simply the stock torque converter doing what's supposed to be doing. And Sarge, I think you're right, the car still seems to be making power during the TC "hiccup."

[TripleTransAm]

Believe me, I've been keeping this issue in the back of my mind all along, especially since I posted an opinion on this and I'd hate to mislead anybody. While I haven't had a chance to try and reproduce the behavior at 3300-3400 RPM (even though I do recall it happening once), I've seen it happen very often at 2800-2900.

Now, this being close to the stock converter stall speed, I'd say that my description holds some potential. However, do you ever experience the same thing at slightly slower accelerations? Or is it ALWAYS at that RPM? Maybe you should verify your converter's stall speed...

[studio460]

Hmmm . . . thanks again for all your informative and detailed posts, Triple-T.

I only recall it happening under moderate-to-hard acceleration. Although funny that you mention in your post about the varying speed/RPMs. I have been noticing the TC kicking in/transferring power (or whatever it's doing) at even HIGHER RPMs and higher speeds. When I recently noticed the behavior at the higher speeds, I immediately relegated the cause to the TC, simply because I could "feel" the TC transferring SOMETHING under there as it performed its (hopefully) routine torque management duties. So about your theory of it being related to stall speed . . . I'm not so sure now. Will try to verify stall speed when I have a chance (how do you do that?)

I've got some DVDs to return to Blockbuster tonight--I'll test specifically for your comments later tonight.

By the way, since this issue's been "in the back of [your] mind" since I first posted it, did that cause you to think it abnormal for the TC to be doing it for any reason? In my car it's awfully repeatable at the exact stated RPMs.

[TripleTransAm]

Originally posted by NBC Shooter
did that cause you to think it abnormal for the TC to be doing it for any reason? In my car it's awfully repeatable at the exact stated RPMs.


I had the chance to drop off my wife before heading to my parents' to drop off my son, this morning, before heading back to work... so that gave me some occasions to 'test'.

Here's some scenarios, we can put these together with what you're seeing and pay attention is anything matches... here's what I did and noticed:

1)
at speed (45-50 mph), press pedal to instigate the TCC unlocking. Since the engine revs about 1500 at this speed with the TCC locked, unlocking it will allow the engine to rev up to as high as the torque converter (TC) will allow (stall speed and then some, since the tranny output shaft is already moving). So in this case, the engine revs up to about 2900. Since I'm running the stock program, I need to slowly add throttle opening to get the tranny to downshift to 3rd and not to 2nd. I think in this scenario (I hope I got the listed speeds correct), the new engine RPM in 3rd gear is STILL under stall speed so the engine RPM barely moves at the downshift. The car is accelerating and then I see the tach begin to inch upward slightly... the tranny output speed is beginning to match the input speed so the engine can begin to climb in RPM.

The tach gets a chance to see 3000 or maybe 3100 before there's a slight surge / hesitation... the engine RPM drops to 2900 once again and I feel a momentary loss of acceleration. I see this as being the upshift to 4th, still no TCC applied. It hangs at 2900 from then on, because I'm in 4th and only slowly accelerating.

Eventually the TCC kicks back in and things drop to 2200 or 2300 or whatever RPM corresponds 1:1 for that tranny gear and speed.


2) Accelerating 'harder' in 2nd gear, the engine RPM eventually climbs above 2900 and about 3300 or so, there is the same surge / hesitation and the RPM drops back to maybe 3000 and I again feel a slight loss in acceleration which immediately comes back after the hesitation. I see this as the upshift to 3rd. Then the TCC locks up and REALLY brings the RPM down.

This 2nd scenario only happens if I'm really driving at 2/3 on the street, and from a complete stop. I rarely see this scenario unless I'm really driving aggressively since I'm in a dense urban area. Usually, this happens at the 2900 with a slight surge back to about 2800 or so, if I'm driving 'spiritedly'.

But I said I did remember having felt it at 3300 at least once, so this confirms what I remembered.


But the only way to prove this is to get an Autotap or some other snooper s/w to watch what your ECM is commanding, to prove that this 'hesitation' is indeed characteristic of a high-stall converter during a transmission upshift.




As for checking stall speed: I believe the technique is to hold the car firmly with the brakes, and apply throttle, watching the engine RPM increase until it reaches a point where it no longer increases. The trick is not to let the rear tires spin (ie. hold the brakes FIRMLY) otherwise you fudge the results... the tranny shaft HAS to be at 0 RPM to get the true engine-side stall speed. This is the listed stall speed. The 'flash' stall speed is what you see when you stomp the gas on a launch, and is slightly higher, since the car begins moving almost right away and you don't have a 0 RPM condition at the tranny side of the TC.

Don't do this for more than 15 seconds or so, since the TC will heat up and in some cases balloon somewhat. Burnouts are fun but toasted trannies are not.

You should see results between 2400 - 2900 RPM for stall speeds. Anything outside of this is out of spec. Older TCs will loosen up beyond 2900... time for replacement (but they gotta be REAL old and worn to do this). Also, you can never trust factory tachs... your tach may read 3000 at 2800 actual RPM, whereas mine may read 2600 at 2800 RPM... factory tachs can be VERY sloppy.

Hope this helps.