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Troy
Dodge Dakota
1/04/2002
09:26:29
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 Subject: tire size affecting shifting
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Message:
Does anyone know if tire size affects the shifting on my truck? I had the dealer switch my 32" tires from my '99 Dakota to my current one the day that I bought it. The truck shifted fine for 10 months after this. Then, with the same tires, it started hitting the rev limiter at the 1-2 shift when floored. I have since switched to 275/65-17 tires which are about 31.3" tall, and the problem still exists. I now have stock 31x10.50-15 tires on, and the problem was happening until the weather turned cold. It shifts fine in this colder weather. I have the stock tires on so the dealer can see that it still won't shift with the "right" tires. However, the weather is messing up the plans. Before the cold weather, the truck would do this shifting problem app. 3-4 times out of 5. Any suggestions would be helpful.
2000 QC Sport Plus 4x4 5.9L 3.92LS, every factory option
equal-length headers and larger y-pipe
Magnaflow single in/ dual out
Autolite 3923's, indexed
Kenne Bell (Taylor) wires
180 stat
Redline Water Wetter
S-bolt
Homemade 4" cold-air induction
Baffled removed from air hat
K&N air filter
Mobil 1 and Purolator
Perma-Cool auxiliary oil cooler
Map sensor mod
adjusted TPS from .568 to .764
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Mar
Dodge Dakota
1/04/2002
12:29:33
| RE: tire size affecting shifting
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Message:
Changing the tire size should do nothing with the transmition. As far as its concerned the driveshafts are still spining the same RPM and the shift points will be the same. Only diffrence will be that the trucks probably going about 5 or 6km faster then before.
Check your fluid level or get a tranny service done. A lot of people on this forum have oversized tires and i havent heard of this before.
Try resetting the PCM. Take of the Neg bat cable and turn the key and hold it on START for about 20 Sec. Then put the cable back on. It should flush out the trannys memory and for the next 200Km should relearn how you drive so drive like you will drive.
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Troy
Dodge Dakota
1/04/2002
17:16:40
| RE: tire size affecting shifting
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Message:
Mar,
I have reset the PCM numerous times, and it did nothing. The truck has 22,000 miles on it, and this problem has been going on since 14,000 miles. Could this be a problem with the transmission internal pressures?
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Aaro
Dodge Dakota
1/04/2002
22:49:09
| RE: tire size affecting shifting
IP: Logged
Message:
Line pressure could be a bit low or TV cable is adjusted to tight
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Joe E.
Dodge Dakota
1/04/2002
23:07:26
|  RE: tire size affecting shifting
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Message:
Think about this, with the larger diameter tire, your tires spin less times at a set speed than they would with a smaller tire. What this means is if your trucks shifting computer is set to shift at a certain speed and RPM, the truck will continue to shift at that computers set level. BUT your tires are outa wack so what your computer thinks you are doing, and what you really are doing, is not the same anymore. This means that you computer is actually being fooled. By thinking that your truck is going faster/slower than it actually is, your shift pionts are off by a bit, causeing wierd shifting areas. If you understand, good.
Its alittle mutteled but hard to explain. But you get the drift. larger tires look great, but do cause things like this. I think 2THEXTRM, got a Superlift "TruSpeed" device which says it fixes all this stuff. Ask him.
Joe E.
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jASON
Dodge Dakota
1/05/2002
00:20:12
| RE: tire size affecting shifting
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Message:
My 97 did this for a few years. I know exactly what you are talking about. I put a trans-go shift kit in my truck in September and the problem has gone away. You have to remember that the computer controls the tranny and can keep it in gear if it is getting bad info from the tranny sensors. The shift kit actually fixed the problem, and I enhanced that by installing a MP PCM which raised the shift points to 5200 rpm!
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Ralph
Dodge Dakota
JOIN HERE
2/22/2002
14:04:43
|  RE: tire size affecting shifting
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Message:
Jason,
What trassmission shift kit did you install? I've been looking for on for my 97 V6 for months and have not found one that fits the application.
Also, what is the difference between a Jet Chip and a MP PCM? I have the Jet Chip currently and I'm not sure if I like it yet.
THanks, Ralph
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Hersbird
Dodge Dakota
JOIN HERE
2/22/2002
17:15:14
| RE: tire size affecting shifting
IP: Logged
Message:
My 93 used to do this as well after a few mods so I switched to the MP PCM and it's higher rev limiter solved it.
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