Auto Tranny Problem

[96mod289]

my car has a problem shifting from 1-2 at WOT and hits the rev limiter. At first i thought i was spinning through first, but last night at the local track with a fresh coat of track prep and BFG DR's at 20 psi it was happening again.

 

[justinschmidt1]

well..from your mod list it looks like you have 4.10s but no tune/....I had the same problem with 3.73s in my auto....

basically the auto cant get ready to shift fast enough becuase the computer thinks your running stock gears or something along those lines...the only thing that Is really gonna get it to shift the way you want would be to get a tune... they will be able to get it to shift wherever you want

 

[96mod289]

well that seems logical- the tranny isnt showing any signs of mechanical problems. this problem is killing my 60 ft time :comando:

 

[nyuk98gt]

96mod289:

While you're at it, you need to get a trans cooler (get a big one) and do the J-mod (see TCCoA.com, find "Transmissions 101" in the Tech Articles/Transmissions section). Your transmission will last much longer and shift way, way better.

HTH,

Chris

 

[96mod289]

i have a hypertech tuner- would it help to firm up the shifts/ shift kit??

 

[nyuk98gt]

96mod289:

The handheld tuner can be used to increase pressure and firm up the shifts. You can go ahead and do it and enjoy firmer shifts. But, know that there is a fundamental disadvantage to just increasing line pressure. The transmission pump generates flow and pressure. If you want more pressure at a particular spot, then flow will be reduced. With a pump, you have to trade one for the other (pressure for flow or flow for pressure). If you firm up the shifts too much with a handheld tuner, you may have robbed too much fluid from the other needs of the transmission (cooling of the innards, for example). So, you get firm shifts but it is costing you long-term durability.

What to do? You need to improve the hydraulics: reduce the pressure loss of the trans fluid by opening up some passages in the valve body [separator plate, to be specific]. This is "the j-mod". By opening up a few holes in the separator plate (a thin metal sheet with specifically sized holes that control the flow of fluid [the plate is attached to valve body] from one part of the transmission to another. With these holes opened up ("j-modded"), the pump can move more fluid at the same discharge pressure. Practically, the shifts are much quicker because the fluid can move through the larger holes faster. And, the quicker shifts can be had without any adverse affects on the cooling needs within the transmission. A major benefit of improved hydraulics is less friction during the shifts so the ATF temperature does not get as hot (as an unmodified transmission). This is how the transmission should have been made to shift from the factory but most drivers like smooth, almost seamless shifts of passenger cars and don't want quicker, noticable performance shifts.

Of course, you can always firm up the shifts more on a j-modded transmission if you desire, too. The key thing is to first open up the circulation system of the transmission so that heat is reduced and durability is improved. Adding some pressure then takes very little flow away from the other parts of the transmission.

Well, it's time I put down my j-mod cheerleader pom-poms. Every auto Mustang should be j-modded and have a tranny cooler added, too, imo.

Chris

 

[dutman98]

I have 4.10's. And I never had a problem. Mine shifts where it always did. I never heard of getting a tune for are cars just for a gear swap. I know you can get a hand held tuner to change the shift points, thats what I would recommend.

 

[nyuk98gt]

dutman98:

The reason that an aftermarket tune for gears is usually required is to account for the faster rate of RPM increase over stock gears. The trans will shift based on vehicle speed or engine RPM, whichever condition occurs first. In the case of RPM shifts, the shift is commanded at a particular RPM and this is set below when the physical shift occurs. There is some anticipation or allowance made (i.e.--time allowed) for the shift to occur. Higher numeric gears will shorten the time between the commanded shift and the physical shift so it is quite possible to hit the rev limiter if the commanded shift point is not lowered a bit. This is not always the case (for example, your transmission shifts OK) but it is very common in our cars (and a tune to adjust the commanded shift points is needed).

Chris

 

[dutman98]

Ok. Im just lucky 8). If you were to tune your car would you want it to shift at max power up in the rpm band, right before it starts to fall off? I can see where this could benifit peformance.

 

[nyuk98gt]

If you were to tune your car would you want it to shift at max power up in the rpm band, right before it starts to fall off? I can see where this could benifit peformance.

dutman98:

Yes, that's correct. And you want to lock the converter right after the shift, too, so no power is lost to slip. A higher stall converter and stickier tires will get the job done at the track.

To get the trans to shift at the max power point, the commanded shift point is nudged up or down until datalogging shows exactly where the physical shift occurs. So, you might end up with a 1-2 shift commanded at 5900 rpm so that the physical shift occurs at 6100 rpm (these are just examples, btw). Track testing/datalogging is needed to fine-tune the commanded shift points.

That's a very entertaining avatar, btw. ;D

 

[Dusstbuster]

96mod289:

The handheld tuner can be used to increase pressure and firm up the shifts. You can go ahead and do it and enjoy firmer shifts. But, know that there is a fundamental disadvantage to just increasing line pressure. The transmission pump generates flow and pressure. If you want more pressure at a particular spot, then flow will be reduced. With a pump, you have to trade one for the other (pressure for flow or flow for pressure). If you firm up the shifts too much with a handheld tuner, you may have robbed too much fluid from the other needs of the transmission (cooling of the innards, for example). So, you get firm shifts but it is costing you long-term durability.

What to do? You need to improve the hydraulics: reduce the pressure loss of the trans fluid by opening up some passages in the valve body [separator plate, to be specific]. This is "the j-mod". By opening up a few holes in the separator plate (a thin metal sheet with specifically sized holes that control the flow of fluid [the plate is attached to valve body] from one part of the transmission to another. With these holes opened up ("j-modded"), the pump can move more fluid at the same discharge pressure. Practically, the shifts are much quicker because the fluid can move through the larger holes faster. And, the quicker shifts can be had without any adverse affects on the cooling needs within the transmission. A major benefit of improved hydraulics is less friction during the shifts so the ATF temperature does not get as hot (as an unmodified transmission). This is how the transmission should have been made to shift from the factory but most drivers like smooth, almost seamless shifts of passenger cars and don't want quicker, noticable performance shifts.

Of course, you can always firm up the shifts more on a j-modded transmission if you desire, too. The key thing is to first open up the circulation system of the transmission so that heat is reduced and durability is improved. Adding some pressure then takes very little flow away from the other parts of the transmission.

Well, it's time I put down my j-mod cheerleader pom-poms. Every auto Mustang should be j-modded and have a tranny cooler added, too, imo.

Chris

I want to J-Mod so bad but I'm deathly afraid of it for some reason...New cams, manifold, exhaust...no problem, but the J-Mod scares me for some reason. Any way you could calm my nerves? I've read the install thing on Tccoa and still don't quite get it all, probably because I'm retarded though.

 

[nyuk98gt]

Dusstbuster:

Have no fear, brother! What worked for me was just reading and re-reading Transmissions 101 and A-Train's how-to articles. I read those things so many times, it became very familiar and the apprehension faded away. I also had the how-to articles on the workbench for easy access and reference. I didn't have a digital camera at the time but I highly recommend taking pictures so you can see how things started out and then progressed as you start to put things back together. Buy the parts and leave them in the open so they remind you that you have work to do, lol.

Here are some other random thoughts:

I didn't remove the eight check balls but you need to remember where they go if you take them out!

There are two little filter "things": one is triangular and the other one is just flat, iirc. It's not obvious where they go but you will see them as the valve body separates from the transmission. Don't be alarmed if the 2-3 accumulator 'keeper' plate falls out -- it just sits up in the bore and is hidden by the valve body.

You might find a yellow plug in the drain pan -- that's an assembly line plug and can be thrown out.

Clean the magnet in the bottom of the pan -- get all the grey "fur" off it. You just need to spray it with brake cleaner and wipe the fur off with shop towels.

You can use kitty litter to soak up any spilled ATF.

When you get ATF on your shirt, it won't come out until wash no. 44 so don't wear any "good" work clothes when you doing this job.

A slightly tricky thing [to remember] is getting the shift lever "finger" in the right spot on the 'manual shift valve' -- that's why a camera is handy. I made a sketch so I got the shift finger located in the right place.

There are 26 bolts and 6 of them are long and go in the "middle" of the valve body and the rest go around the perimeter of the valve body. When reinstalling, you have to hold the v/b up and get two of the long bolts in with about 5 full turns to hold the v/b in place. Put the rest of the bolts in and finger tighten them a little at a time so the v/b is pulled up against the transmission evenly. Torque them to 30, then 60 , the 90 lb-inch and CHECK THEM ALL TWO OR THREE TIMES AGAIN (sorry for yelling, I'm just nagging). And, you want to torque them in a criss-cross pattern, doing the long bolts first, then the outside bolts -- kind of like doing the cylinder heads or lug nuts on a wheel.

I have to tell you that I WAS an auto transmission chicken but by reading those articles over and over and feeling comfy with the procedures, I am not a tranny chicken any more! You did your cams and went through the timing procedure and this is much easier (honestly) and does not take near as long.

Now, if you really don't feel comfortable in the end about doing the j-mod, then I suggest that you try a local Mustang board and ask for a local trans shop or a member/technician who will do it for you. Or, if you already have a favorite shop that does big jobs that require special tools or a lift or something that you can't tackle at home, ask your shop guy if he will do it. It will cost you some loot but you won't lose sleep.

LMK if you have any other questions. :thumb:

Chris

 

[96mod289]

Lots of goooooood info- thanks man