thinking about doing the jmod.. couple questions

mark8smine

mark8smine

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im swapping my old trans into my 97 base.. trans has 150,000 as far as i know.. anybody think a jmod would kill the trans or would it hold it? curious cars coming back apart this winter so im not really worried about it but dont want to kill a good trans. anybody out there have one done that has high mileage? trans is out so i figured might as well right? lol
 
Sapperfire said:
Personally, I'd save the jmod for a 98 trans
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yea? i was just debating on it because the things out and wouldnt be hard to do while i got everything apart ya know? was more curious to see how much harder it shifted from stock. guess ill just wait cars coming back apart im going to cage it and back half it.. just wanted to run around in it a little before i start tearing into it this winter
 
Doing the j-mod on any 4r70w will help it to last longer... If you have the time, I say do it!
 
chris2523 said:
what is peoples strange fascination with 98+ trans? the older stuff is just fine for stock power levels.
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The 98 and newer trans came with upgraded springs and pistons from the factory. Anything older than a 98, and it is highly recommended that you replace the 1-2 and 2-3 piston and springs. The springs tend to break, and the pistons can bind. Both cause l-o-n-g shifts.

I've had 2 93's and both of them had broken 1-2 springs when I took them out to do the JMOD. My 97 had been upgraded by the previous owner, but not JMOD'ed. I upgraded everything in my 96 when I did the JMOD, but nothing was broken.

In all cases, leave the 2-3 spring OUT! It's not necessary, and the 2-3 shift is almost perfect without the spring.
 
rrudd2 said:
The 98 and newer trans came with upgraded springs and pistons from the factory. Anything older than a 98, and it is highly recommended that you replace the 1-2 and 2-3 piston and springs. The springs tend to break, and the pistons can bind. Both cause l-o-n-g shifts.I've had 2 93's and both of them had broken 1-2 springs when I took them out to do the JMOD. My 97 had been upgraded by the previous owner, but not JMOD'ed. I upgraded everything in my 96 when I did the JMOD, but nothing was broken.

In all cases, leave the 2-3 spring OUT! It's not necessary, and the 2-3 shift is almost perfect without the spring.
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I thought broken springs made it shifter harder. :confused:
 
rrudd2 said:
The 98 and newer trans came with upgraded springs and pistons from the factory. Anything older than a 98, and it is highly recommended that you replace the 1-2 and 2-3 piston and springs. The springs tend to break, and the pistons can bind. Both cause l-o-n-g shifts.
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i'm aware. that upgrade is cheaper than a 98 trans.
they also came with an upgraded mechanical diode for 2nd gear.

rrudd2 said:
I've had 2 93's and both of them had broken 1-2 springs when I took them out to do the JMOD. My 97 had been upgraded by the previous owner, but not JMOD'ed. I upgraded everything in my 96 when I did the JMOD, but nothing was broken.
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i replaced my accumulator pistons and springs at 140k. looked fine. factory trans went on to 170k. 2nd gear scratch til the day it died.

rrudd2 said:
In all cases, leave the 2-3 spring OUT! It's not necessary, and the 2-3 shift is almost perfect without the spring.
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yeah i wouldn't do that. definitely not in all cases. my jmod and chip can chirp the tires half throttle 1-2. spring is in. i've seen many cases where people put that spring back in. too harsh.


but still, my point is, at factory power levels, a pre 98 trans does work fine. you can even put in the new accumulator and upgraded diode if you really want to. you do not "need" a 98+ trans.

sbcaprice305 said:
I thought broken springs made it shifter harder. :confused:
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yes. a symptom of a broken spring is the harsh shifts.
a messed up accumulator will shift slower though.
 
chris2523 said:
what is peoples strange fascination with 98+ trans? the older stuff is just fine for stock power levels.
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It's true that the pre- 98's are fine for normal power levels but there were some good things added to the 98's that would likely keep you worry free of shudder and allow you to do manual 1-2, 2-3, 4-2 shifts, like the intermediate one way clutch and also, in 98, the friction material was swapped over to a better, longer lasting material.

picture02.jpg


So if one were to be on the hunt for another transmission, an extra $50 to $100 would be worth getting the 98 and re-pinning to work with the 93-97's or just swapping out electrical internals and like mentioned above, the accumulators and springs are already upgraded. There were a few more things done with the 98 trans to make it last longer and function a lot better.
 
My friend has his 97 j modded at 190k. It is the original transmission. Today the car has 207xxx on the original drivetrain and it still shifts perfectly.
 
chris2523 said:
i replaced my accumulator pistons and springs at 140k. looked fine. factory trans went on to 170k. 2nd gear scratch til the day it died.
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This is what the 1-2 looked like in my Blue 93 when I did the JMOD:

old12.jpg



chris2523 said:
yeah i wouldn't do that. definitely not in all cases. my jmod and chip can chirp the tires half throttle 1-2. spring is in. i've seen many cases where people put that spring back in. too harsh.
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None of my cars are chipped, so I hadn't considered that. A very valid point, the JMOD plus the increased line pressure settings in the chip would probably have you sideways pretty quickly!

chris2523 said:
but still, my point is, at factory power levels, a pre 98 trans does work fine. you can even put in the new accumulator and upgraded diode if you really want to. you do not "need" a 98+ trans.
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Not disputing that at all, as evidenced by the fact that I did the JMOD on the original tranny on all 4 cars, none of which is a 98. I was trying to answer the "why would you want one", without realizing you were asking a rhetorical question!

chris2523 said:
yes. a symptom of a broken spring is the harsh shifts.
a messed up accumulator will shift slower though.
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Spot on. I screwed that one up in my post.
 
rrudd2 said:
This is what the 1-2 looked like in my Blue 93 when I did the JMOD
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how many miles?

rrudd2 said:
None of my cars are chipped, so I hadn't considered that. A very valid point, the JMOD plus the increased line pressure settings in the chip would probably have you sideways pretty quickly!
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chip + jmod, don't even consider flooring it in the rain. lol. just don't.
 
this shouldnt even be a question. do it.


when i did mine i also upgraded the pistons to the new ones. the springs wernt broken but i changed them out anyways
 
I'll do mine next week. I have everything but decided to get the 1-2 cover and a new circlip just to be safe. I will take my chances on the 2-3 spring, I have the 1-2 springs and both pistons.

The upper separator plate gasket was the hardest thing to find.
 
rrudd2 said:
The 98 and newer trans came with upgraded springs and pistons from the factory. Anything older than a 98, and it is highly recommended that you replace the 1-2 and 2-3 piston and springs. The springs tend to break, and the pistons can bind. Both cause l-o-n-g shifts.

I've had 2 93's and both of them had broken 1-2 springs when I took them out to do the JMOD. My 97 had been upgraded by the previous owner, but not JMOD'ed. I upgraded everything in my 96 when I did the JMOD, but nothing was broken.

In all cases, leave the 2-3 spring OUT! It's not necessary, and the 2-3 shift is almost perfect without the spring.
Click to expand...

should i leave it out or what then? others are saying not to...

vr4 said:
this shouldnt even be a question. do it.


when i did mine i also upgraded the pistons to the new ones. the springs wernt broken but i changed them out anyways
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what did that cost?

rrudd2 said:
That was right about 114k. We've put another 50k on it since it was JMOD'ed.
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thats not bad at all, i think this is going to happen now. i just didnt know if it beat the trans up or not. definitely looking into parts now
 
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