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Discussion Starter #1
hey guys i just did the jmod to my 1997 mark 8. i did the exact thing as a couple of my friends did (same springs, drilling holes etc) and they can bark the tires on 1-2 but i cant at all. my shift is firmer but is smooth as glass. any ideas why i cant rip the tires?
 

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what springs did you put in/leave out? what specs did you drill to?
 

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Discussion Starter #3
the top 1-2 spring and no spring in the 2-3 and drilled to the mildest settings.
 

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I did the 300+ specs on my '97 Mark (non LSC), shifts are nice and firm, no problem breakin' them loose on a moderate acceleration 1-2 shift. The mild is probably too mild for the Mark...do you have 3.08 gears? If so, that could be the biggest factor.
 

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I noticed you said the TOP 1-2 you have it backwards...it's needs the top and remove the bottom
 

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I didnt think u had to jmod on any tranny after 95. maybe i should look at the articale again.
 

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NightWind said:
I didnt think u had to jmod on any tranny after 95. maybe i should look at the articale again.
Reread the article again.

Very few changes have been made to the 4R70W since the article was written (new/better valvebody after '99 I believe is the major thing)...this is ignoring the small variances between TCC's over the years.

You can do the mod to any 4R70W...new or 'old.' We did it on an '01 GT a while back. You just have to do it to the proper settings. On the newer 4R70W's, some of the holes are already the right size...

Silver95bird would know a hell of a lot more than I would on such a subject...
 

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66dvlbrd68 said:
Silver95bird would know a hell of a lot more than I would on such a subject...
what am i now, some kind of expert? lol. just kiddin around... i'm getting to know my way around a 4r70w bit by bit over time.

outside18,

Maybe your car has different gears/axle than the ones you're comparing to... also possible that your tires are sticky and your friends aren't! :)
my 95 was done with only an upper 1-2 spring, no lower 1-2 spring, and no 2-3 spring... it used to come close, but almost never chirped the tires. I'm assuming you've got the same spring setup, if you don't then try the above. Assuming thats the same, then if you're really unhappy with it, you could try something higher for the specs- marks are close to the 300hp level, so maybe the next higher specs would work, though they'll add more stress to the u-joints and rear end. ... or you could do it the easy way and buy a chip. One of the good chip suppliers from this site could do what you want in a way that wouldnt add undue stress to the tranny. I'd kind of prefer it to be done via a chip, but some ppl can't afford that readily.

Just keep this in mind if you decide to redrill: If you want only the 1-2 shift stiffer, only redrill the #2 hole. And go up in small increments... its easy to make them bigger, but you'd need a new plate if you drilled the holes too big. Try a bit around .090" before you go to a .100" bit. You may find it only needs that tiny bit more to get what you want.
 

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Tom,

I did the mod for his car and both his friends. The #2 hole was drilled out to .100" with the #39 bit. His friends have 96 and 97 T-Birds so they're running the 3.27 gears, not sure about the Mark VIII gears though. The 1-2 piston has the top spring and the 2-3 has no spring. He also has a rebuilt tranny in that also. Could there be something there that would cause this? Just a thought.

Joe
 

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Joe,

Okay, that helps a bit. If he's already at .100", he's either got good tires 225 wide or bigger, or his rear end is probably a 3.08. I'd say the rebuild didn't affect it. When I had my 95 (w/3.27 trak-lok) I never drilled the 5.4L tranny to .100" and it would WOT chirp 1-2 some times, but that tranny has a different EPC solenoid. That's the only thing affecting the shift really... hole size, line pressure, and resistance (via rear, tires, etc).

related technical rant (for those interested):
Many of us j-modders hear the serpentine belt squeal on a wot shift ... it squeals because the speed of the crank pulley changes faster than the belt has traction to slow. same concept, only opposite side of the driveline. The output shaft is accelerating slowly at the top of the rpm range in 1st gear, and as the rpms come down when 2nd gear engages, the acceleration changes. The faster the shift the bigger the change. The tires, being mechanically linked to the output shaft of the tranny, are also experiencing the same acceleration changes. when the change is too large, the torque load of the engine on each wheel/tire overcomes the friction of the tire.... and voila! *CHIRP* It's a jerk, in the scientific aspect of the word.

That's also why gears play a part. as the rotations of the tire in relation to the rotations of the output shaft of the trans change, so does the acceleration.
Shift kits change the amount of time it takes the clutches to apply/exhaust, thereby making the acceleration changes faster and feel more sudden.

Okay I've gone on long enough. that's way too much for what most people want to know, lol.
 

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Another thing to consider when opening up that 1-2 clutch/accumulator feed hole is that the larger you make it, the lower the RPM the shift will occur - to a point. Remember that the ECC sends the shift signal slightly before the shift is to occur - enough to overcome the fill time of the clutch and accumulator. The delay is based upon the rear-end ratio, engine torque, and clutch fill rate.

What all this means is that if you have a 3.8L engine and a 3.27 rear-end and the ECC expects the engine to take 1.8 seconds to reach the desired shift RPM from where it is currently, it sends the shift solenoid signal that amount of time early. When you reduce the fill rate the shift occurs sooner - possibly so early that you're not even in the peak power band of the engine...

Overdrilling the holes with a stock motor or one with a lower power output that recommended could result in too early a shift. A stock 3.8L N/A coupled to a transmission drilled out to 450HP is a mistake!

FWIW
 

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Great info guys...IMO, it really sounds like he's got 3.08's and (maybe) some stickier tires or low tire pressure (since hole #2 is the same for mild and 300+ settings). That DOHC should have no trouble overcoming the friction of the tire ( tire, singular, all Marks have open rear ends)

Oustside18, tell us if your Mark is an LSC or not! Also, if you really want to make some noise out back, turn off the traction control as soon as you start the car. On mine, the TC can react fast enough to apply the brakes, eliminating all but the hardest of shifts.
 

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Discussion Starter #15
ok guys, im a 97 non lsc. i have a 3.08 rear end which will be changing to 4.10 this winter. i do notice that the traction control light comes on when i take it to wot then let off the gas right before the shift. thats when it feels hardest. when im at wot the shift is literally as smooth as glass.
 

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but during that time that the computer sets away for shifting in the stock setting, isnt power not being applied anyway? if it's taking that long to shift, then it's out of gear that long correct?
could ET's actually go up with a modification like this?
 

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And you are sure you put the 1-2 accumulator spring on the top? Meaning - towards the top of the car/tranny? That is strange... What happenes when you do a manual 1-2? Even with the milder settings, this is almost guaranteed to cause a rapid engagement. If you put the spring on the bottom by mistake, it will probably never shift hard at WOT - this is the factory 'mildest shift' arrangement.
 

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Discussion Starter #18
no way. Joe and I definitely but the spring in the top. we wouldnt have messed up like that. my cars just weird. we will see what i chip does with it. now that its sitting in my room with my dual exhasut. ill let everyone know when i install the chip and see the difference.
 

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chilipepprflea said:
but during that time that the computer sets away for shifting in the stock setting, isnt power not being applied anyway? if it's taking that long to shift, then it's out of gear that long correct?
could ET's actually go up with a modification like this?
Not certain I understand what you are saying, but automatics don't 'release' anything between shifts - not like a straight shift. The only thing the tranny does to shift into '2nd' is apply the intermediate clutch. The FWD clutch is already applied when in first - apply the intermediate clutch, and it's second. It's never 'out of gear'.
 

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outside18 said:
no way. Joe and I definitely but the spring in the top...
There is one other possiblilty, however unfortunate. :(
If the car is high mileage, or has had a lot of hard 1-2 shifts in it's life, the intermediate clutch pack may just be worn out. Weak pump pressure can also do this, as can a really scratched up accumulator bore, leaky acc. cover., and bad intermediate clutch piston seals. Just something to consider...
 
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