Anyone "slipping" at 3200-3300RPM?

[studio460]

Hi all. Thanks to all for all of your extremely well-informed, helpful posts--I've been addicted to this site ever since I first discovered it a few weeks ago! Here's the question:

In a three-week old 300B, I've noticed an odd "slipping" in the transmission/torque converter (?) which I noticed in the first few days. This anomaly can be repeated by slow to moderate acceleration only. While accelerating in second gear, as you reach 3200-3300RPM, the tach oscillates slightly, and it feels like the drivetrain is "slipping" (I believe this happens in third gear as well, only less noticably). This "hesitation" lasts for about one second. After this effect passes, the RPMs rev normally to its shift point a few hundred RPMs later. Any others experienced this? Is this an example of the "shudder" characteristic reported of Crown Victoria torque converters (do Marauders have differect TCs?)? How do I "prove" to the service department that something's wrong?

Thanks in advance.

[cyled]

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.

[studio460]

cyled:

Thanks for your quick reply! So you feel that "oscillation" at 3250RPM too? (Which is still about 300-400RPM BEFORE the stock shift point)? Yes, well, I hope all is normal . . . and yes, I am VERY interested in the Stallion torque converter mentioned here. Chip, plugs, stat, and 4.10 mods are an absolute no-brainer from what I've heard from all of you good people here. Just as soon as I work out some minor warranty repair issues--I'M THERE! Thanks again!

[Macon Marauder]

'Shooter:

Not sure if this is the same thing as what you experienced, but:

Before the chip, my Marauder would "surge" under moderate acceleration. It didn't really feel like what I would call slipping. I base this on having owned older Fords which had very slippery transmissions. :)

My Marauder would feel like it "just wanted to go but couldn't" or was "confused."

I know this probably doesn't make much sense. But anyway, Dennis' chip fixed all that - somehow.

[RF Overlord]

shooter:

The chip definitely changes the shift characteristics of the transmission. I didn't have mine stock long enough to notice any "slipping", but it did up-shift WAY too soon, and entered OD and lock-up too soon as well. With the chip, first and second are held much longer...and it won't shift into OD until about 42 MPH.
(under part throttle; believe it or not, I don't do WOT very often...I actually don't find it necessary!)

[TAF]

You're right Macon.

And Shooter, we have talked here several times about how the stocker "hunts" for gears sometimes. Dennis' chip is programmed perfectly and fixes all this. As well, a good professional install of 4:10S will yeild nice firm and precise shifting.

[WolfeBros]

^^^ What they said ^^^^
The chip will fix your problems. :up:

There is a downside.......everyone will wonder why you are grinning all the time while driving in LA traffic. :D

[RF Overlord]

Originally posted by WolfeBros
everyone will wonder why you are grinning all the time while driving in LA traffic.

Grinning all the time in LA traffic is a sure way to keep people FAR AWAY from you...those LA drivers are all loco in the cabeza...

...almost as bad as Marauder drivers from DALLAS!

[russ in VA]

Help me out here becuase I'm new to slushboxes (WISH they built a 6-speed Marauder), but I am confused about the reference above that says that the high stall converter helps get traction without burning the tires off the line. Isn't that just the opposite of what a high stall converter does? Isn't the idea that that it lets the engine rev up into the power/torque band before "biting" so that the car will launch harder? I know that personally I was very frustrated driving this car in the snow BECAUSE I could not modulate the launch. That is, even when I tried to accelerate very gradually to prevent wheelspin as soon as I hit that 2000-2500 range where the torque converter grabs it would just break loose. I've also noticed that when trying to drive like a chauffer and launch quickly but S M O O O O T H L Y, it seems to be impossible because any prod of the loud pedal produces a noticable neck snap as you go past 2 grand. I am hopping that once I get Denis's chip (and 4.10's) that I will be able to launch at part throttle more smoothly. I've never corresponded with him, but I have been planning to ask him if he could custom burn me something (if his standard chip won't do it) to get RID of the high stall effect so I could launch smoothly. I'd like the tranny to grab right off idle and I don't care about being able to rev it up sitting still so I can burn the tires from a stop anyhow, I'd just preffer something with as little slip as possible. However, I DO like getting a nice bark on the 1/2 shift at WOT which I have found is possible with the stock car if you perfectly time a manual shift! Perhaps the chip can do that for me too? Denis you listening? If not I'll email you.

[TripleTransAm]

Originally posted by cyled
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.


With all due respect, Cyled, that is not 100% correct.

The main purpose of a torque converter (like the older pre-'65 fluid couplings) is to take the place of a manual transmission's clutch in an automatic, allowing smooth upshifts and idling at a stop without stalling in gear. However, what makes a torque converter a torque converter and not a fluid coupling is the added presence of a "stator".

The operation of a fluid coupling (and TC) is like putting one of those kids' toy pinwheel fans in front of a household electric fan... the pinwheel fan will begin to twirl because of the angle of the blades, driven by the air thrown at it by the electric fan (or when you blow into it, for example). The stator takes things one step further and 'accelerates' the oil inside the TC onto the driven side, allowing for torque multiplication on take-off. Once the TC stops slipping (ie. the driven side speed begins to match the driving side ie. engine RPM), the stator ceases to multiply torque.

The torque multiplication factors are usually along the lines of 2 - 2.5 . That means that when you slam your foot on the gas pedal and the RPM immediately shoots up, you're actually delivering a momentary 2 - 2.5 times the torque of the engine at that speed into the tranny! Once the car is underway and the slippage is reduced, the multiplication factor returns to around 1:1 ( and actually hits pretty close to 1:1 once the torque converter clutch engages, negating any TC effect).

By tuning the angles of the vanes inside the TC, you can play with the slippage rate. In a heavy car like the MM with an engine that is more comfortable at midrange than at low RPM, allowing the engine to 'flash' to 3000 RPM (or whatever the stall speed is) will allow the engine to reach a meatier portion of the torque curve sooner, and delivering that 2x whallop at that point. With a tighter converter, the engine would only flash to something lower like 1800, and the launch would not be as impressive.

This is why drag racers with engines modified to run high RPM power but with totally crappy low end will use insane TC stall speeds, sometimes >4000 RPM! Makes for awesome launches, but try launching the same car at 1500 RPM and it's bog city (if the engine doesn't completely stall!).

[TripleTransAm]

Originally posted by russ in VA
I have been planning to ask him if he could custom burn me something (if his standard chip won't do it) to get RID of the high stall effect so I could launch smoothly.


I don't believe this is possible since the high stall speed is a result of the internal construction of the TC. The angles of the vanes on the "turbine" and "impeller" sides (and the stator vane angle as well!) will dictate stall speed. What is controllable on today's torque converters (post-1980) is converter clutch application speeds and conditions.

What I believe NBC Shooter was experiencing is the TCC wanting to apply in 2nd gear before the upshift to 3rd. Sounds like an economy thing, and I'm fairly confident a reprogrammed chip will move this engagement point out of your hair in 2nd gear. Engaging the TCC under moderate acceleration in a ratio like 2nd gear could bring about the shudder that is described... it is, after all, just a friction surface like a manual clutch and will try hard to grab during application under power.

History lesson: in the 60's, Buick offered a "switch-pitch" torque converter as an option. You could have the TC set to a low stall speed for smooth city driving, or activate an alternate setting which would actually rotate the TC internal vanes slightly to increase stall speed for a more dramatic launch.

[RF Overlord]

Originally posted by TripleTransAm
History lesson: in the 60's, Buick offered a "switch-pitch" torque converter as an option...

Damn, 3TA, you're GOOD...I was gonna put a "switch pitch" in the Turbo 400 in my GS about 25 years ago, but when I found out you needed a new front pump and other mods to the tranny (which I had just paid a racer buddy to rebuild), I never pursued it...didn't know any better at the time... :(

[WolfeBros]

Originally posted by RF Overlord

...almost as bad as Marauder drivers from DALLAS!

Bastage :D

[WolfeBros]

Originally posted by RF Overlord
...didn't know any better at the time... :(

Since when did you know better at any time ?? :lol:

[martyo]

Wolfe: Leave RF alone. Today is a national holiday for him! Give him the respect he deserves.

[CRUZTAKER]

Originally posted by RF Overlord
...almost as bad as Marauder drivers from DALLAS!


After nine days as an impartial, unbiased, non-local observer.......

PICKUP DRIVERS IN THIS TOWN ARE CRAZY WILD!!!!!!


On topic, the chip upgrade WILL correct shifting issues, positively, absolutely. Customer service aside, buy the RPC chip, great solution vs cost.

[WolfeBros]

Its the soccer Mom's in SUV's you have to watch out for. :rolleyes:

[TripleTransAm]

Originally posted by WolfeBros
Its the soccer Mom's in SUV's you have to watch out for. :rolleyes:


In my area, it's the soccer moms in SUVs, for sure. But then there's the young 'uns in daddy's BMW or Mercedes that are 'making a mark' in my neighborhood. Last Sunday, I saw a silver BMW 3 series straddling a fence on the highway and the marks on the grass indicated a long graceful sideways exit off the paved surfaces. *sigh*

If firearms were commonplace up here, I'm sure my neighborhood would have become a war zone by now, with the way people disregard others' safety.

MM content: I've noticed that when driving around my parents' area of town (where I grew up, and came to enjoy driving), folks will drive REAL slow when I'm behind them. :D In my current neck of the woods, though, seems there is no respect for the local police anyway so no one flinches at the sight of my MM anyway. :rolleyes:

[Mark McQuaide]

Great stuff, TTA - keep it coming! A real education!

[TripleTransAm]

A few years back, I scanned and uploaded some diagrams of how a 3 speed automatic delivers the different ratios using a gear system very different from the traditional manual tranny system. If anyone's interested, here are the links:

http://firebird.freeservers.com/tech/1stgear.jpg

http://firebird.freeservers.com/tech/2ndgear.jpg

http://firebird.freeservers.com/tech/3rdgear.jpg

http://firebird.freeservers.com/tech/reversegear.jpg


There's also a very simplistic side-view of how a torque converter works:
http://firebird.freeservers.com/tech/converter1.jpg
The illustration shows a non-lockup type of converter... the lockup clutch would be located between the turbine (blue) and the forward facing side of the TC, which would interface with the flywheel (shown in the image as actually part of the flywheel for some reason).

[cyled]

The torque multiplication factors are usually along the lines of 2 - 2.5 . That means that when you slam your foot on the gas pedal and the RPM immediately shoots up, you're actually delivering a momentary 2 - 2.5 times the torque of the engine at that speed into the tranny! Once the car is underway and the slippage is reduced, the multiplication factor returns to around 1:1 ( and actually hits pretty close to 1:1 once the torque converter clutch engages, negating any TC effect).

TripleTransAm....

Your point is taken. I explained in non technical terms the fact that people have complained about not smoking the tires from launch and that the torque converter is part of the issue. With no data to back it up, but just thinking how Mercury wants to keep from replacing parts, it is working by design.

Maybe you can help clarify the fact that there seem to be different types of "Stall" converters. Some seem to not "engage" until a certain RPM is reached and then BAM! they dump the power. Others (like in the Marauder) seem to slowly allow power through until they reach a certain rpm and then lock out.
Either way, the one in the Marauder seems to design to help prevent form tearing up the drivetrain and aid with traction from the factory.

I have no issue if you can show me my errors in my ways.. :-)
I am always willing to learn more...

[TripleTransAm]

Originally posted by cyled

Maybe you can help clarify the fact that there seem to be different types of "Stall" converters. Some seem to not "engage" until a certain RPM is reached and then BAM! they dump the power. Others (like in the Marauder) seem to slowly allow power through until they reach a certain rpm and then lock out.


I can't say I have a tremendous amount of seat time with converters of different stall speeds, but it has been my understanding thus far that the higher stall speed converters are the ones that exhibit the 'BAM' nature you described. Usually, these are the 'built' small block Chevys with 3000-4000 RPM stall speed converters... below stall speed the oil isn't being whipped up against the turbine enough to transmit much torque but once it reaches that stall speed, the oil begins to really transmit some push. I keep remembering a friend who owned a 1970 Camaro with a built 350, who works for SLP. His co-workers urged him to go for a high-stall converter, and he says it ruined the car's driveability on the street (the behavior you described), whereas it was docile with a lower-stall-speed TC previously.

One other possibility is that different TCs from different companies behave differently as they approach stall speed. Even identical TCs behave differently behind different engines... a 1600 RPM TC from a Chevy 305 resulted in a 2200 RPM stall speed when used behind a mildly-built Pontiac 400.

In contrast to the small block Chevy I mentioned above, the 4.6l is well-known to be a little soft at the bottom end. Even though Ford saw fit to spec a much looser TC to allow the engine into the powerband a little quicker, I think they were still conservative enough such that there was no 'neck-snapping' by reaching a stall speed too high for street driving. As far as Ford's reasons for their TC stall speed choice, it's been publicized as being in order to aid the launch performance. With something like a 1600 RPM stall speed, the MM would NEVER spin a tire... it would reach maximum torque multiplication at a speed where the engine wasn't making all that much power.

Theoretical example: at 1600 RPM, the engine delivers 100 lb-ft. At 3000, it delivers 300 lb-ft.

With a 1600 RPM converter (using a stator multiplier of 2.00), flooring it would result in an immediate ~1600 RPM and an instantaneous application of 200 lb-ft at the tranny input. With a 3000 RPM stall speed (same multiplier), the engine flashes to 3000 RPM and whallops the tranny with 600 lb-ft. So I'd be inclined to say a yet higher stall ratio in the MM would result in a more aggressive (ie. harder) launch.

In the absence of more technical knowledge on the matter, I'd have to say the behavior you described is a matter of matching the TC to the engine's nature and power curve.

Also, if you don't mind, I may spend a little time looking up some TC manufacturer data before commenting further. I'd like to back up my comments with some more research.

[TripleTransAm]

http://www.kirtland.cc.mi.us/auto/Aut218notes/Aut218notes.htm

Here's a good one outlining converter clutch shudder. I think a 'chip' would help this situation, provided it raised the converter clutch application RPM to where the speed differences between turbine and impeller are already minimal (imagine the difference in clutch behavior if you dropped the clutch on a manual car at 5000 RPM versus 1500).
http://www.c2c-auto.com/what_is_torque_converter_shudd er.htm

This site has some good descriptions, except they are incorrect in saying the overdrive lockout will also lockout the converter clutch operation. Not true, you still get converter lockup in 2nd and 3rd even with OD off.
http://www.leeric.lsu.edu/bgbb/7/ecep/auto/f/f.htm


And what looks to be my favorite site for info:
http://auto.howstuffworks.com/torque-converter.htm
The links (especially the FAQ link) are great!

[TripleTransAm]

http://www.familycar.com/transmission.htm#Torque%20Conv erter

[studio460]

Thanks to all!

You guys are great--thanks for all the tutorials on drivetrain mechanics . . . I finally found and read the FAQ . . . I guess this is normal, then? Really looking forward to installing Phase I + Stallion TC . . .

[SSMOKEM]

I'd like to add my 2 cents' worth, since I had 3 different converters in my Impala.

The stock 12" one stalled to around 1400. This was fine due to the high amount of torque available fairly low, max torque came in at 3000. Not a lot of slippage at all and worked well with the 3.08 gears.

After I added a cam and ported the stock heads, I went to a 2400 12" stall. I discovered that I had no power between the stall speed and 3000, where the cam came in.

I then went to a 9.5" 3800 stall converter. All I could say was WOW!!! It was one of the best mods I had done to the car. It does take some getting used to. At normal city speeds, I need to be around 3000rpm to cross the steep bridge over the Intracoastal by my house. At WOT (wide open throttle), it slips around 7%, since it's not a lockup type. Bottom line is that you need to have a much greater throttle angle to reach the same speeds you used to get just by lightly pressing the pedal.

However, normal driving is pretty much the same as before. If you let off the brake, it will still creep a bit at lights. A light tap of the pedal will still get you moving, but at a much slower rate.

Check out this chart, showing how my RPM stays in a very narrow range at WOT. This run was on the juice, and the converter stalls to almost 4500 due to the extra torque:

http://www.cadwiz.net/cherrybomb/RPMcurve.jpg

[TripleTransAm]

Originally posted by SSMOKEM
Bottom line is that you need to have a much greater throttle angle to reach the same speeds you used to get just by lightly pressing the pedal.


Thanks for confirming this, George. I was under the impression that this was indeed the case with looser converters.

Today was the first day I took out the MM in days (been ugly weather, I figured the Honda could take the abuse instead) and while I did not notice a 'shudder' per se, I did notice that in some cases the TC application made me think it was an additional gearshift (with the ensuing RPM drop). This RPM drop might be misconstrued as a hesitation, even though there was no cessation of forward acceleration.

The application of the TCC was extremely noticeable in manual 2nd gear... I was in stop-and-go-and-stop-and-stop-and-stop-and-go traffic this morning and decided to move forward by holding the tranny in 2nd gear. Acceleration was, as expected, kinda soft but I was surprised the TCC application was so noticeable.

[SSMOKEM]

Hey Steve,

The Chevy trannies, and I'm willing to bet, also the Ford ones have PWM (pulse width modulation) of TCC clutch apply. In the Impalas we can just program for softer or harder apply, and I'm sure Reinhardt could do the same for you guys.

The downside is, the softer it applies, the more it wears. We found it best to apply it past 50mph for smoother city driving.

[TripleTransAm]

Originally posted by SSMOKEM

The Chevy trannies, and I'm willing to bet, also the Ford ones have PWM (pulse width modulation) of TCC clutch apply.


You're right!! I forgot about that since my youngest GM automatic is currently 16 years old, and I'm not sure if they had adopted that PWM application technique. I too recall this was to soften the often-brutal clutch application. The TCC application in my '87 GTA is very noticeable in 3rd gear (it upshifts to 3rd before the 2nd gear application point so that's not an issue)... it's as noticeable if not more than an actual upshift! I actually like it like this... I am among those who prefer more positive auto-tranny-clutch applications in order to minimize wear. And the nice low end torque of the TPI motor means I actually accelerate FASTER once the TCC locks up, under steady pedal pressure. In other words, once the TCC engages, the car shoots forward and I have to back off to a feather weight on the pedal to keep road speed.

Any clue when GM went to PWM? For that matter, can anyone out there confirm that this is Ford's method for TCC application?

[SSMOKEM]

Hey Steve,

I have a TH400 with manual valve body, so no clutch apply :)

In the Impalas, they added PWM to the 4L60E in 1995.

[Katmandu]

Originally posted by russ in VA
I know that personally I was very frustrated driving this car in the snow BECAUSE I could not modulate the launch. ...

I'll be GLAD to swap my P71s (Crown Vic Police Interceptor) TC for your MM TC !! :P :P :D :D

Seriously, anyone want to sell me your used MM TC after you upgrade to a Stallion ??

[TripleTransAm]

http://www.victrans.com/multiplication.html

[martyo]

Kat, pm me or e-mail me if you are serious about wanting my MM converter.