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#1
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I have just started building up my 318 in a 90 dodge truck with an eight foot bed. I have already rebuilt the transmission and the rearend. the problem that I am having is my shift points. I have been told that a new computer would take care of that problem, but i don't know anything about them. What do I need to look for and where?
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#2
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A new "computer" won't solve the problem.The shift point is determined by throttle pressure via linkage/cable from the carburetor/throttle body to the transmission valve body.What exactly is the problem???
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#3
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My problem is with my shifting. when I am really getting into the throttle the transmission will not shift from first to second. I have a Transgo shift kit with brand new bands and clutches. I seem to have a rev-limiter that keeps first gear from reaching the 5000 rpm that the shift kit is looking for. The rest of the gears shift right on time. I have adjusted the linkage a few times to try and dial it in, but have had no luck. will a high performance computer remove that rev-limiter?
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#4
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I've snooped around with this asking various people over the years, and I've sort have concluded that the max rpm shift points are programed into the valve body. Not programed like with a computer, but valved in such a way that the shift occurs when the trans fluid reaches a certain pressure. I have a 1991 318 in a short box 4x4, it shifts at 4000, my 85 4x4 Ramcharger and my 72 3/4 ton motorhome van chassis both are exactly the same. I have been looking for the facts on this situation, not real hard or anything, and I do know that the computer does not control the shift in these years of transmissions, and the throttle pressure controls shift points at all conditions less than full throttle. Now you know what I know, please post any other info you come up with, I'll be listening.
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#5
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Shift RPM is determined by the govenor weight that is located at where the tailshaft meets the main trans case.In order to change the weights,you'll have to pull the tailshaft off as per a Mopar service manual.This can be done in the vehicle.Some of the Transmission shops in the Mopar magazines sell these govenor weights that will alter the RPM shift point.I think,and I may be wrong on this,Mitsubishi weights will fit a Torqueflite.I will look into this a bit further.
[This message has been edited by Christopher (edited May 28, 1999).] |
#6
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OK Christopher I have obviously been asking the wrong people, would I be correct in thinking the weights can be changed on a 4x4 transmision, and if I put a set on from a car transmission I will now have the same shift points as the car had, or does vehicle weight alter this formula in any way.
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#7
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You would be correct although the extra weight of a 4x4 MIGHT throw the shift point off a bit,but I wouldn't think very much,maybe a couple of hundred RPM at the most.Also Mopar has had two different weight diameters,so if you find one in say,a old 340 Dart that shifted at 5000,the diameter is different than in your 4x4,so you would have to change the weight retainer too,but that's an easy job too.
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#8
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This is my problem, the tranny will shift in and out of gear when going from first to second when I race. The shift kit wants 5000 rpm but the tranny will only allow 4300-4500rpm. Will changing the weights on the tail shaft allow for the extra 500 to 700 rpm so it can shift? If so, does mopar make these weights for a 500 tranny?
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#9
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Yes,changing the weight will give you the increase in RPM that you want.The problem is that Mopar changed the diameter in the weight at some point and a older weight won't work.(like out of a 340 Duster)I know of some that will work,but I will have to look in my book of notes for sources you can get these from.May take a day or so.O.K. I found it,the weights you can get from A&A transmission (317)831-5610 The weight from a 2.5 Jeep #4617173 will give you a higher upshift.Central Jersey Motor Parts (732)446-3738 has a slant 6 governor kit (NOS part)that will upshift at 4800 rpm.That's all the info I have.You may want to get friendly with your local dealer parts man and see what he can look up too.
[This message has been edited by Christopher (edited June 02, 1999).] |
#10
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Christopher, thanks for your help. I have used A&A transmission before and have had good luck. I will get back with you with the results. thanks again
[This message has been edited by wildcat (edited June 03, 1999).] |
#11
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I have ben looking to remove my rev-limiter in my 1990 dodge with a 318. I have been told that a new computer would do this> I have been trying to get reach Mopar Performance but the line is always busy. I need to know if there is a replacement computer for my vehical and how I can get one. or is it possable to change the rev-limiter with a high performance valve body?
[This message has been edited by wildcat (edited June 15, 1999).] |
#12
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I believe the deal on the diameter of the govenor is that 727 govenors are larger that 904 based trannys. Also Mits built Dodge Arrow used a 904 transmission with a high (lightweight) govenor. I've read that when the govenor is installed it should give you around 6000 rpm shifts in drive.
If your computer won't let the motor rev that high, I think that the only thing to do is to go with the "old" tech way. Put in a carb, distributer, and electronic ignition and let the motor rev to where YOU want it to. As far as I know I don't think that there is much out there for computer upgrades for pre-Magnum EFI motors. I could be wrong. There is another thought and that is that if there are no other modifications to the motor, would there be any reason to rev the motor beyond the stock range? Dunno. If it's a low speed torquey motor there may not be any reason to run the revs up. |
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