Gang:

Have any of you experienced this? I have a bone-stock truck, low mileage. Everything works just fine and it's a strong runner.

Sometimes if I punch it in first and run it right up to the 1-2 shift point, then lift the throttle right as the transmission wants to shift (for traffic or whatever), it will SLAM into second gear incredibly hard. Basically, it feels like getting rear-ended by some flimsy little European sport coupe (like an Audi TT).

This is often accompanied by a brief, sharp squeal. Not sure if it's the tires, supercharger drive belt, or something else.

Any ideas? At all other times, the thing shifts annoyingly soft (the dreaded 4-cylinder cutoff).

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Silver Y2K Lightning
Bone Stock w/ Duraliner, Ford Hitch Cover

Best 60-foot: 2.041
Best 1/8: 8.872
Best 1/4: 13.789
Best MPH: 99.67

Silver (matching) Y2K ML320 Benz
Burl (ML430) Shift ****
Best Run: 17.137@80.629 (2.550 60-foot)

1992 Grand Prix SE
Commuter Mule, G-Tech 17.3 @ 81

 

I can't explain the mechanics of it, but I can tell you that's what happens when you hammer it to the shift point, let off then hit it again once it's committed to the shift. Kicks you right in the a$$ !!!

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<A HREF="http://users.ev1.net/~temurphy/lightning/" TARGET=_blank> </A><A HREF="http://haloclub.svt-lightning.com" TARGET=_blank> </A>
2000 Black Lightning
#4399

 

Has something to do with trans. pressure. I've noticed it a couple of times.
If you back off right before the shift, it'll hit hard.

The squeal?
Betcha' it's an Audi owner that saw you break the tires loose.....

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Rich
1999.5 SVT Lightning - Red. 100HP Shot NOS, NGK TR6 Plugs, BellTech 3/4 drop, Ford MotorSport Chrome Lightning wheels, Super Chip(TRAC). K&N Filter. Viper Alarm w/remote start, Sir Michael's roll pan, smooth corners and steps w/billet inserts, clear corner lenses, Cervinis Ram Air hood, ARE Cover w/ wing, Momo billet pedals, cd changer, cover, Phantom boost and nitrous gauges, MTX Thunderform w/ 2 10" MTX Thunder 4000 subs. 5-channel 500w. Clarion amp.(APA5241), (4)Polk Audio 3-way, 130w. DX 7's, Color-matched Muth signal mirrors, Soundproofed cab, BedRug, Trenz billet grills, Piaa 9007 Super Whites, etc. Build #2755
TampaSVT@Tampabay.rr.com

http://home.tampabay.rr.com/tampasvt/

2001 Lexus IS-300
2001 EB Expedition

[This message has been edited by TampaSVT (edited 05-03-2001).]

 

Here is a guess.

The electronic shift strategy is programmed so that the speed and firmness of a shift is dependent on the amount of power going through the tranny. If the shift is soft under full power it will take ages to shift and destroy the clutches.

Since it is a mechanical system, it has a certain amount of lag/transition between reading the line pressure and shifting. If you lift on exactly the right moment, 2 problems exists:

1) the pressure is high enough to shift, and since you are lifting, the rpm too. So you get the shift that was planned for 5000 rpm and WOT, at 4000 rpm and 1/4 throttle. It will bang a little.

2) the shift can not be delayed too long, since you are running in open torque converter mode and the fluid is getting churned. Otherwise the shift could be delayed until the line pressure has dropped sufficiently to give a softer shift.

The problem is what will happen if you get on the gas again during this time of waiting for the line pressure to drop...

Solution:
Don't lift !

 

Yeah. What BlackLight said!

A guess, huh? - hehehe

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<A HREF="http://users.ev1.net/~temurphy/lightning/" TARGET=_blank> </A><A HREF="http://haloclub.svt-lightning.com" TARGET=_blank> </A>
2000 Black Lightning
#4399

[This message has been edited by Madhouse (edited 05-03-2001).]

 

Yeah, mine's done that on the 2-3 shift, only without the squeal. It hit so hard I fully expected to see gears and u-joints following me down the road.

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Jim
Black '00
#1,757 built 3/30/00
Clear corners
JDM street program
JDM 2# blower pulley (ordered)
J.L. Stage II ram-air
FRPP Oval throttle body
90mm MAF
MagnaFlow Exhaust

 

Mine did the same thing.

 

Not an L owner but the same thing happens to me if I floor it then let off right before it shifts. I don't hear a squeal though.

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1997 XLT Teal 4.6L Flareside 4x4 ORP. Automatic, Reg. cab, 3.55LS, tinted windows, bug deflector, Dual exhaust, K&N Generation 2 air filter, BullDog keyless entry/remote start, Modern 16" wheels, bedliner, Covercraft tonneau cover, White faced gauges, electronic shift on the fly, Clarion ADX5655z Double Din Cassette & CD, 4 Pioneer TS-A6865 speakers and superchip.

Future mods: Supercharger, headers, NOS, tranny upgrade(heavy duty gears, clutch packs, etc.), performance torque converter, composite driveshaft, bore cylinders 30 over, new pistons, crank, and rods, get performance heads or port the ones I have, gauges for the a-pillar, new L if they still make them and I like the way it looks, and a Z06 Vette or BMW Z3.




Click here to see more pictures

 

The squeal is the SC belt slipping. The engine decelerates rapidly as the tranny hits 2nd, and the blower rotors have to catch up (or "catch down" I guess).

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Mark
'00 Lightning
'79+ Corvette

 

'2K-SVT,

Sounds like Blacklight's assessment is on the money IMHO.

Where is Factory Tech?

 

That squeal is becasue we don't have a good belt tensionoir on this truck. to much play with the stock one. thats why I'm making my own to torque that belt down as tight as possible.

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I get the same hard slam on the 1-2 shift only when I run it up and then have to let up suddenly ( like... gumball spied in the bushes)It's so hard that I fully expect the rear end to rip loose. I still have a firm hard shift driving in a normal manner on the 1-2 shift. I have a weird slip on the 2-3 shift. My dealer says its normal, my gut says it anin't. Happens at any speed.
BTW, I have a 98 e-150 conversion van with a 5.4 and the same jarring 1-2 shift as described above happens with it under the same situation.
aLSO.. The squeal isn't the audi owner...check your ram air duct, mighta sucked the whole audi up in there....

 

I've almost got used to it...If you want to have fun, try to fool the computer. Let up on the gas, and just as it kicks you in the @ss, kick the throttle open again. You can circumvent the 4 cyl upshift thingy, and burn the tires on the 1-2 shift. I've done it a couple of times, but the timing is tricky.

 

Same thing happens to me, too. The 1st time it happened, I could've sworn that the truck hopped up off the road. Now I try to let up after the shift, but I usually run out of road, or I catch up to the car in front before it shifts.

 

RTKILLA
Seems like I remember a while back some one posted that they had a problem with the shaft bearing caused by over tightening of the belt. Might be worthwhile to do a search and find out the details.