why does my jmod feel weak? - TCCoA Forums
 
LinkBack Thread Tools
post #1 of 27 (permalink) Old 08-20-2003, 11:59 PM Thread Starter
 
Join Date: Oct 2002
Posts: 107
why does my jmod feel weak?

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?
outside18 is offline  
Sponsored Links
Advertisement
 
post #2 of 27 (permalink) Old 08-21-2003, 12:13 AM
Seasoned PostWhore
 
Silver95Bird's Avatar
 
Join Date: Aug 2002
Location: Gouldsboro, PA
Age: 36
Posts: 3,178
what springs did you put in/leave out? what specs did you drill to?

96 Mustang GT 5spd. w/ 248A Option (GTS). Stock for now until I get the Roush on.

97 Thunderbird 4.6L LX /w Sport Package
24k B&M Cooler, 1" lowered, Steeda UD Pulleys, Dynomax cat-back, J-mod, 3.73's, PI intake, PI cams, 03 GT MAF/Tube, SCT tuned - Gone but not forgotten.
MAMN12 Drag Racing Team [email protected] In need of updated times.
Silver95Bird is offline  
post #3 of 27 (permalink) Old 08-21-2003, 05:26 AM Thread Starter
 
Join Date: Oct 2002
Posts: 107
the top 1-2 spring and no spring in the 2-3 and drilled to the mildest settings.
outside18 is offline  
Sponsored Links
Advertisement
 
post #4 of 27 (permalink) Old 08-21-2003, 09:19 AM
 
Join Date: Jul 2002
Posts: 647
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.
Blown306 is offline  
post #5 of 27 (permalink) Old 08-21-2003, 11:50 AM
5w30 Guzzler
 
chilipepprflea's Avatar
 
Join Date: Jul 2002
Location: Columbus and Athens, Ohio
Age: 35
Posts: 1,462
Send a message via AIM to chilipepprflea
surely traction control and trac-lok will keep it from being wild.
chilipepprflea is offline  
post #6 of 27 (permalink) Old 08-21-2003, 12:29 PM
02 Explorer Pioneer
 
timb's Avatar
 
Join Date: Jul 2002
Location: Cumming, GA
Age: 52
Posts: 2,880
I noticed you said the TOP 1-2 you have it backwards...it's needs the top and remove the bottom

Birdless

There is no limit to what you can acheive if you don't care who gets the credit.
timb is offline  
post #7 of 27 (permalink) Old 08-21-2003, 07:50 PM
5th Gear Poster
 
NightWind's Avatar
 
Join Date: May 2003
Location: New Jersey
Posts: 468
Send a message via AIM to NightWind
I didnt think u had to jmod on any tranny after 95. maybe i should look at the articale again.

Yeah if i wasn't half a sleep I could write better, but sleep is over rated...?
NightWind is offline  
post #8 of 27 (permalink) Old 08-21-2003, 08:12 PM
Astrophysicist / PostWhore
 
66dvlbrd68's Avatar
 
Join Date: Jul 2002
Location: Albuquerque, NM (visit NM!)
Age: 38
Posts: 2,028
Quote:
Originally posted by NightWind
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...

Mike | RSW | THP | MF | SRTConnection |

1996 Ford Thunderbird LX V8 + 1992 Ford Mustang hatchback + 1989 Ford Mustang notchback = no where else to park at my house!
66dvlbrd68 is offline  
post #9 of 27 (permalink) Old 08-21-2003, 08:25 PM
5th Gear Poster
 
NightWind's Avatar
 
Join Date: May 2003
Location: New Jersey
Posts: 468
Send a message via AIM to NightWind
Quote:
Originally posted by 66dvlbrd68


Reread the article again.
So I'm a bad speller so sue me!!!!!

Yeah if i wasn't half a sleep I could write better, but sleep is over rated...?
NightWind is offline  
post #10 of 27 (permalink) Old 08-21-2003, 11:24 PM
Seasoned PostWhore
 
Silver95Bird's Avatar
 
Join Date: Aug 2002
Location: Gouldsboro, PA
Age: 36
Posts: 3,178
Quote:
Originally posted by 66dvlbrd68
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.

96 Mustang GT 5spd. w/ 248A Option (GTS). Stock for now until I get the Roush on.

97 Thunderbird 4.6L LX /w Sport Package
24k B&M Cooler, 1" lowered, Steeda UD Pulleys, Dynomax cat-back, J-mod, 3.73's, PI intake, PI cams, 03 GT MAF/Tube, SCT tuned - Gone but not forgotten.
MAMN12 Drag Racing Team [email protected] In need of updated times.
Silver95Bird is offline  
post #11 of 27 (permalink) Old 08-21-2003, 11:40 PM
MA Chapter Director

Administrator
 
Rodeo Joe's Avatar
 
Join Date: Jul 2002
Location: Franklin, MA
Age: 63
Posts: 7,967
Garage
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

It's not a 97 Sport, it just looks like one!

Mass. TCCoAers, Send me your info!

I buy all my Ford parts from 93 lx.

Member of the TCCoA Damage Control Team.

R.I.P. Johnny Langton 1975 - 2011
Rodeo Joe is offline  
post #12 of 27 (permalink) Old 08-22-2003, 01:11 AM
Seasoned PostWhore
 
Silver95Bird's Avatar
 
Join Date: Aug 2002
Location: Gouldsboro, PA
Age: 36
Posts: 3,178
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.

96 Mustang GT 5spd. w/ 248A Option (GTS). Stock for now until I get the Roush on.

97 Thunderbird 4.6L LX /w Sport Package
24k B&M Cooler, 1" lowered, Steeda UD Pulleys, Dynomax cat-back, J-mod, 3.73's, PI intake, PI cams, 03 GT MAF/Tube, SCT tuned - Gone but not forgotten.
MAMN12 Drag Racing Team [email protected] In need of updated times.
Silver95Bird is offline  
post #13 of 27 (permalink) Old 08-22-2003, 01:57 AM
 
Join Date: Jul 2003
Posts: 306
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
GregFL is offline  
post #14 of 27 (permalink) Old 08-22-2003, 09:55 AM
 
Join Date: Jul 2002
Posts: 647
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.
Blown306 is offline  
post #15 of 27 (permalink) Old 08-22-2003, 09:59 AM Thread Starter
 
Join Date: Oct 2002
Posts: 107
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.
outside18 is offline  
post #16 of 27 (permalink) Old 08-22-2003, 10:02 AM
5w30 Guzzler
 
chilipepprflea's Avatar
 
Join Date: Jul 2002
Location: Columbus and Athens, Ohio
Age: 35
Posts: 1,462
Send a message via AIM to chilipepprflea
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?
chilipepprflea is offline  
post #17 of 27 (permalink) Old 08-22-2003, 10:07 AM
 
Join Date: Jul 2003
Posts: 306
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.
GregFL is offline  
post #18 of 27 (permalink) Old 08-22-2003, 10:09 AM Thread Starter
 
Join Date: Oct 2002
Posts: 107
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.
outside18 is offline  
post #19 of 27 (permalink) Old 08-22-2003, 10:11 AM
 
Join Date: Jul 2003
Posts: 306
Quote:
Originally posted by chilipepprflea
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'.
GregFL is offline  
post #20 of 27 (permalink) Old 08-22-2003, 10:19 AM
 
Join Date: Jul 2003
Posts: 306
Quote:
Originally posted by outside18
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...
GregFL is offline  
post #21 of 27 (permalink) Old 08-22-2003, 10:25 AM Thread Starter
 
Join Date: Oct 2002
Posts: 107
>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...



well thats just the thing. the transmission is brand new. i had it replaced under warranty about 3 months ago.
outside18 is offline  
post #22 of 27 (permalink) Old 08-22-2003, 10:33 AM
Seasoned PostWhore
 
Silver95Bird's Avatar
 
Join Date: Aug 2002
Location: Gouldsboro, PA
Age: 36
Posts: 3,178
Quote:
Originally posted by GregFL
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.
Yes it certainly does affect the RPMs of the shift. Again, my 95 as an example: With the silencer and K&N panel in, some times at WOT it would just barely touch the rev limiter at about 5250 RPMs... after the J-mod it shifted at 4700 every time. But there is a limiting point - if I drilled it out twice as large, I doubt I'd see more than 100-200 rpms difference (i'd have to research, not 100% sure)... but i'd have a break-neck shift that would have me changing my u-joints with each oil change . The parts breakage would be a bigger concern than the shift RPM at that point.

I'm assuming that the car doesn't have a million miles on the rebuild... so the seals and clutch packs should be okay as long as the rebuild was done right. The pump may be worn, but you could put a line pressure guage on and check that fairly easily. The accumulator stuff outside18 or Joe might already know... we'll see.

96 Mustang GT 5spd. w/ 248A Option (GTS). Stock for now until I get the Roush on.

97 Thunderbird 4.6L LX /w Sport Package
24k B&M Cooler, 1" lowered, Steeda UD Pulleys, Dynomax cat-back, J-mod, 3.73's, PI intake, PI cams, 03 GT MAF/Tube, SCT tuned - Gone but not forgotten.
MAMN12 Drag Racing Team [email protected] In need of updated times.
Silver95Bird is offline  
post #23 of 27 (permalink) Old 08-22-2003, 10:35 AM
5w30 Guzzler
 
chilipepprflea's Avatar
 
Join Date: Jul 2002
Location: Columbus and Athens, Ohio
Age: 35
Posts: 1,462
Send a message via AIM to chilipepprflea
Quote:
Originally posted by GregFL


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'.
ok sorry for not understand/being confused. the idea was thrown at me earlier that the earlier shift points would be compensated for by the fact that it shifts quicker. is this wrong?
will my basically stock bird suffer from the 300hp setting?
chilipepprflea is offline  
post #24 of 27 (permalink) Old 08-22-2003, 12:22 PM
 
Join Date: Jul 2003
Posts: 306
Quote:
Originally posted by Silver95Bird


Yes it certainly does affect the RPMs of the shift. Again, my 95 as an example: With the silencer and K&N panel in, some times at WOT it would just barely touch the rev limiter at about 5250 RPMs... after the J-mod it shifted at 4700 every time. But there is a limiting point - if I drilled it out twice as large, I doubt I'd see more than 100-200 rpms difference (i'd have to research, not 100% sure)... but i'd have a break-neck shift that would have me changing my u-joints with each oil change . The parts breakage would be a bigger concern than the shift RPM at that point.
Yup, That is why I said - 'to a point'. You do reach a point (around ~.090") where further drilling does little more than increase shock loads - if you aren't running a HO motor and upgrades in the drivetrain this results in broken part$.

This is one of the things I slightly modify on the JMod for my own use. Especially on the 3.8L engines with their lower output, the shift occurs too soon for my taste with the .081" settings. Without looking back at records, I think I have been using .0785" 1-2 feed holes on the 3.8L applications.
GregFL is offline  
post #25 of 27 (permalink) Old 08-22-2003, 06:25 PM
 
Join Date: Aug 2003
Posts: 168
On my '95 @300HP mod level with 3.08 rear you've got to back off to avoid a chirp!
How 'bout a couple of other thoughts?

Valve block properly torqued?
Separator plate Flat?
Cleaned old gaskets completely?
New gaskets properly positioned?
Check balls all in proper position?
Mercon V fluid?

Have you checked stall speed in all gears?
Does the trans make any unusual noises at idle (in park, neutral, or any gear).

DR
DRROVER is offline  
post #26 of 27 (permalink) Old 08-22-2003, 09:51 PM
 
Join Date: Jul 2002
Posts: 286
Another possibility - does anyone know if the 97 PCM he's got pulls timing during the upshifts to smooth out the torque bump?
bill_s is offline  
post #27 of 27 (permalink) Old 08-23-2003, 02:01 AM
 
Join Date: Jul 2003
Posts: 306
Don't know offhand, but I wouldn't think it would have a great effect.
The inertia of the rotating parts already at 5,000RPM is generally what causes the 'tire spin effect'. Ignition retard wouldn't slow these down much, although it would ultimately effect the continuation of the spin after full engagement - assuming there is enough power being created to overcome tire friction, etc....

FWIW
GregFL is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the TCCoA Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome