Trex cam and Vacuum Modultor??
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Trex cam and Vacuum Modultor?? Since I put the Trex cam in, the Tranny doesn't downshift right. When I'm cruising around 35 mph and nail it from 3rd gear, it won't even downshift or come out of lock up. When on the freeway cruising at 70 mph it down shifts fine. I'm wondering if the Vacuum modulator is not functioning right with the Trex, maybe the vucuum is to low and not giving the right line pressure's. I also notice I'm bouncing off the 7400 rpm rev limiter with 6500 rpm shift points, any idea on that one? It's a pro Yank tranny with 12K on it, mods in the sig..BTW, I had none of these issues with the TR230 two weks ago.
TIA,
Dan
TIA,
Dan
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Originally Posted by T/A Medic
too much power now ... u need a Th400 
I guess I'm just gonna pull this Vacuum Modultor out and let the PCM control the line pressure. Something is causing this and this is all I can think of. It shifts gears real fast too now, meaning it goes from 1-2 and 2-3 shifts befor I get to 30 mph then it goes to lock up right away in 3rd gear. Maybe it's time for a new car
Dan
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Originally Posted by DanZ28
Ahhhh Great!! Another big expense
I guess I'm just gonna pull this Vacuum Modultor out and let the PCM control the line pressure. Something is causing this and this is all I can think of. It shifts gears real fast too now, meaning it goes from 1-2 and 2-3 shifts befor I get to 30 mph then it goes to lock up right away in 3rd gear. Maybe it's time for a new car
Dan
I guess I'm just gonna pull this Vacuum Modultor out and let the PCM control the line pressure. Something is causing this and this is all I can think of. It shifts gears real fast too now, meaning it goes from 1-2 and 2-3 shifts befor I get to 30 mph then it goes to lock up right away in 3rd gear. Maybe it's time for a new car
Dan
Don't do that. Vacuum modulation is the key. It doesn't have anything to do with the shift timing. It only has to do with shift firmness. 0 vacuum = 100% line pressure. You downshift problem has to be in the programing. Good luck to you.
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I've been tuning the hell out of this thing, but the tranny perameters look good. I have the shift points at 6500 rpm for now, I'd like them back to 6900 rpm when this is resolved though. Shift timing is only half the problem, why does it not downshift at low rpms (under 2000)? Could low vacuum down low cause this to happen?
JFM, you have any similar issues?
Thanks guys!
Dan
JFM, you have any similar issues?
Thanks guys!
Dan
Backround.
Dan,when my car was dyno tuned back in November the PCM-Trans section got screwed up somehow.The trans would start in the gear selected meaning if in OD,it started in OD,barely moved.The stock trans had over 400 passes on it so we thought the dyno killed it.We installed another used tranny and it did the same thing so we went back to the tuner and he "reset"the trans section.It took him a few tries to get it right[by right I mean you could put it in OD and it would shift on its own],he said something about not having any shift points set.The used trans was a POS and I had my stocker rebuilt.
Issue:I start in OD and the 1-2 is fine,2-3 is fine BUT at 30 MPH it feels like it locks up[in OD or is it 3rd ?]then downshifts and holds to about 38MPH and locks up in OD.If I start the trans in D,the 1-2 and 2-3 are fine but when I shift to OD it feels like it,unlocks or lags than locks in OD.My thought is that the shift tables are still not right.I am tired of waiting to get it 100% right so it will go to the track and I will try it in D and see what happens.
I rolled the gas on in 2nd[took a couple tries because it was blowing the tires off] and it shifted out to 3rd great,I cant test the 1-2 shift until the Hoosiers Drags go on at the track.
Dan,when my car was dyno tuned back in November the PCM-Trans section got screwed up somehow.The trans would start in the gear selected meaning if in OD,it started in OD,barely moved.The stock trans had over 400 passes on it so we thought the dyno killed it.We installed another used tranny and it did the same thing so we went back to the tuner and he "reset"the trans section.It took him a few tries to get it right[by right I mean you could put it in OD and it would shift on its own],he said something about not having any shift points set.The used trans was a POS and I had my stocker rebuilt.
Issue:I start in OD and the 1-2 is fine,2-3 is fine BUT at 30 MPH it feels like it locks up[in OD or is it 3rd ?]then downshifts and holds to about 38MPH and locks up in OD.If I start the trans in D,the 1-2 and 2-3 are fine but when I shift to OD it feels like it,unlocks or lags than locks in OD.My thought is that the shift tables are still not right.I am tired of waiting to get it 100% right so it will go to the track and I will try it in D and see what happens.
I rolled the gas on in 2nd[took a couple tries because it was blowing the tires off] and it shifted out to 3rd great,I cant test the 1-2 shift until the Hoosiers Drags go on at the track.
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jfm, our issues are definately different, but shifting into lock up in (D) at 30 mph is the same as I have. These big *** cams of ours may be causing this issue somehow, specially since the TR230 had none of these issues two weeks ago before I swapped to the TRex. Maybe the PCM thinks there is less or more of a load than there really is and causes it to lock up and shift early. I would invest in Edit and start doing this your self. The shift points are easy to set and it's by RPM at WOT.
Since I have the Vacuum mod, if my vacuum is low at part throttle, that would increase line pressure right at low RPM right? What if I have to much line pressure at low RPMs, would it cause this wierd behavior?
Dan
Since I have the Vacuum mod, if my vacuum is low at part throttle, that would increase line pressure right at low RPM right? What if I have to much line pressure at low RPMs, would it cause this wierd behavior?
Dan
Dan,when you said it shifts gears real fast now and goes OD at 30 mph is same here but mine seems to lock at 30 then unlock and relock in OD at 38 to 40.
I guess HP Tuner or Edit will fix my shift tables.
I hope you get yours sorted out it sucks slamming the rev limiter.
I guess HP Tuner or Edit will fix my shift tables.
I hope you get yours sorted out it sucks slamming the rev limiter.
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I made a little progress last night by going back to an old tune. It seems to down shift better now, don't know why, the tranny perameters are Identical. It's still not right, but better. Once it goes to lock up in 3rd (gear selector in 3rd) at 30 mph and I floor it, it takes a good 2-3 seconds before it drops out of lock up and down shifts. I think I'm gonna adjust the lock up speed so it just won't lock till a much higher MPH. I think with our high stalls and big cams, it just needs some extra tweeking.
Mine also unlocks between 3rd (D) and OD (actually moving the shifter from 3rd to 4th)at about the same 37-38 mph. I don't think I would actually want mine to stay locked through a shift. Are you saying yours while in OD or 4th gear it will lock in third then when it shifts, unlocks, then relocks again?
I hope you get that worked out soon to because I really want to see some new 10 sec. track times from you...
Dan
Mine also unlocks between 3rd (D) and OD (actually moving the shifter from 3rd to 4th)at about the same 37-38 mph. I don't think I would actually want mine to stay locked through a shift. Are you saying yours while in OD or 4th gear it will lock in third then when it shifts, unlocks, then relocks again?
I hope you get that worked out soon to because I really want to see some new 10 sec. track times from you...
Dan
TTT, interesting... I have the same problems but my cam is waaaay smaller, 222/224 .571"/.571" 114 LSA. I do have 3.73 gears in the back which I figure contributes to the wacky shifting (I don't believe the shift points stuff was ever changed from stock settings). Unfortunately my tune is locked and there's no way to change it so I'm living with it.
Yank 3000 2.0 STR, TransGo shift kit, 2 washers.
I'd sure like to know what causes this low speed downshift problem though.
Bad30th
Yank 3000 2.0 STR, TransGo shift kit, 2 washers.
I'd sure like to know what causes this low speed downshift problem though.
Bad30th
Dan, sorry to hear about your problems. Please try this one little part of your tune out. Go into the the fuel air tables, there is a part, MIN MAX MAP should be 55/45 or close to that. Anyway, add 10 to each one and then go try the trans downshifting.
After installing the TSP 231/237 cam in my A4, one of the 1st I guess, had the same problems your talking about. Trans would go right up to overdirve, like leave a sto light, 1-2-3-4, then sometimes come back to 3. But if I nailed it right then it would hold that gear. I never got on it to check the rev limiter before I fixed the shift issues. But try it out, it cant hurt anything.
I dont have edit on my wofes computer, I am on leave before I deploy so I am thinking of which page, but at the center maybe bottom half, you should see two drop boxes, one over the other. Min & Max MAP, with a set of ##, just add 10 to each one and go try it. Thanks,
Charlie
After installing the TSP 231/237 cam in my A4, one of the 1st I guess, had the same problems your talking about. Trans would go right up to overdirve, like leave a sto light, 1-2-3-4, then sometimes come back to 3. But if I nailed it right then it would hold that gear. I never got on it to check the rev limiter before I fixed the shift issues. But try it out, it cant hurt anything.
I dont have edit on my wofes computer, I am on leave before I deploy so I am thinking of which page, but at the center maybe bottom half, you should see two drop boxes, one over the other. Min & Max MAP, with a set of ##, just add 10 to each one and go try it. Thanks,
Charlie
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Hey Charlie, thank you so much for the info, I'll try that out tonight
Bad30th, I would send your PCM back to who ever locked it and make them unlock it! That is a bunch of crap if you ask me, locking your PCM so no one can see what the hell is going on. That PCM belongs to you and it should NOT be locked, that would **** me off if someone did that to mine. There is no way you can find out if something is messed up with the tune, and for that matter have someone else or yourself tune it again. Send it back and make them unlock it. You payed for that tune, you own it!
Sorry for the rant
Hope you get it worked out, but sounds like you need to tune it to fix it..
Dan
Bad30th, I would send your PCM back to who ever locked it and make them unlock it! That is a bunch of crap if you ask me, locking your PCM so no one can see what the hell is going on. That PCM belongs to you and it should NOT be locked, that would **** me off if someone did that to mine. There is no way you can find out if something is messed up with the tune, and for that matter have someone else or yourself tune it again. Send it back and make them unlock it. You payed for that tune, you own it!
Sorry for the rant
Hope you get it worked out, but sounds like you need to tune it to fix it..Dan
Sounds like a EW tune. And tuners look at their work like head porters do, its their art and art shouldnt be copied. Whats that saying locks are for keeping honest ppl honest!
Anyway, I hope this MAP reading will work for you as well. There was a few of us with the 231/237 cam having the same problem. I forget which guy figured this out, but its worked for me and quite a few others.
Again, good luck and please let me know if this works.
Charlie
Anyway, I hope this MAP reading will work for you as well. There was a few of us with the 231/237 cam having the same problem. I forget which guy figured this out, but its worked for me and quite a few others.
Again, good luck and please let me know if this works.
Charlie
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Hey CAT3, are you talking about the Fuel Air Multiplier? Did you adjust yours from the lowest 20 KPA up to 55 KPA by adding 110% (10%) to all fields? I did that and your right, it down shifts way better now. Thanks for the huge tip my friend! Saved me a ton of time..Have you noticed any side affects to anything else by adjusting this field?
Dan
Dan