Diablosport Forums

2003 Mustang V6 w/automatic/4R70W, latest revision, U7146.
When I'm going at partial throttle, approx 35mph and then realize I am in a 25mph zone and lift off the throttle partiallly, its shifing into 4th gear and I have OD turned off and always turn OD off when I start the car. I believe the 4R70W automatic is a 3speed with OD making it a 4speed. There doesn't seem to be a partial throttle rpm shift times modification on this model, just WOT. I have a PI stalllion 2800 stall converter and 3.73 gears w/tractionLok. Other engine mods but shouldn't be related to this issue. This also happens when I'm going about 45mph to 50mph and slightly let off the throttle. The problem is that the Shifter it self only has a 1st, 2nd and D, so I can't stay in 3rd if I want either. This isn't really an issue if I'm going 45 to 50mph but it's a problem at the lower 35mph speeds because it will lug the engine going into the 4th. Any ideas as to why this is happening ? Do you think someone before me modified this tranny to be a 4speed with OD ? which doesn't seem likely. Should I put the stock tune back in it and see if it still does it.

In third gear, the torque converter will lock up at light throttle. It's not very noticable with the stock converter, but with a higher stall converter it would be. I'd bet that's what you're feeling. Either that or your OD switch isn't working. Does the, OD off, light come on in the cluster?

4648 wrote:In third gear, the torque converter will lock up at light throttle. It's not very noticable with the stock converter, but with a higher stall converter it would be. I'd bet that's what you're feeling. Either that or your OD switch isn't working. Does the, OD off, light come on in the cluster?

Howdy
Yep, the light comes on and I always turn off OD when I start the car. I have the tune automatically turn off rev and speed limiiter as well as traction control. I adjust the torque modulation, shift firmness and rpm wot shift points.

Now that you mention it and although it's been a while since I put the torque converter in, pretty sure it was after that mod that I started feeling that. I've tried turning od off and on while I'm driving as well but I get the same results. It just simply feels like I have a fourth gear all the time and it's a pain at lower speeds around town because it brings the rpm's down like a fourth gear ratio would.

When I'm driving down a 55mph hwy rather than freeway it shifts into that fourth gear and then when I push the OD button to put it in Over drive and it shifts into overdrive just like it should as well. One thing that's strange about that fourth gear is that the rpm's must be a very close ratio to 3rd because the rpm's dont' go down a bunch just a liittle bit. Like I said, and it happens all the time and I can feel it most at lower speeds because it lugs the engine and I know why it lugs the engine of course since I have the stall converter set at 2800.

My stall is set at 2800. Maybe I should take it down to 2600, I don't know. I chose 2800 because when I did the test of just watching my rpm guage from a dead stop and punched it, I got 2800rpms which of course is one of ways to choose which stall to go with. Most of the time if I'm only going 25 to 30mph and it does it, I shift into 2nd if it lugs too much. The Gears helped with that lug feeling a little bit as well and I can get out of that lug feeling faster now after the gear upgrade than I could before putting gears in.

I'm stumped on this one. I really like the stall it's at for the most part. It's just in these down town streets where the speed limit is 25 that it bothers me. If i shift into 2nd at 25 to 30 mph I'm at about 2500 rpm's I think so it's not real bad to have to do that. I just wish there was a easy fix for it which in my opinion is if this tuner had the option to choose partial throttle shift ponts as well like some of the valve body shift kits etc..out there.

It seems like if the predator had the option to change rpm shift points for partial throttle conditions, that would help but it just has WOT rpm shift points to adjust. That part works perfect so I wish they had a partial throttle shift point option. I could get a shift kit and upgrade the valve body and be able to do partial throttle shift points, I just like the predator and really don't want to do that if I don't have to.

Anyone with DiabloSport know if they may come up with a upgrade for the U7146 that would permit partial throttle shift points for our 4R70W trannys in the future or could I get a custom tune?
I think that would help a lot seems like to me and I'd appreciate that Big Time. If not, and if I upgrade the valve body to one that supports both partial and wot shift points, will that mess up the options with my Predator ? Thanks for the response

4648 wrote:In third gear, the torque converter will lock up at light throttle. It's not very noticable with the stock converter, but with a higher stall converter it would be. I'd bet that's what you're feeling. Either that or your OD switch isn't working. Does the, OD off, light come on in the cluster?

I feel it is related to the converter as well.