Trans issue - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 10 (permalink) Old 09-11-2010, 12:57 AM Thread Starter
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Trans issue

My 2001 24valve 4X4 auto truck switches back and forth between 3rd and 4th gear at 35 mph. Does anyone have any sugestions about if this is a computer issue or a mechanical issue.

2001 Dodge ram 2500 auto 4x4 cummins. 4.10 gears, 285 tires. Superchip, CFM+ intake, K&N air filter, 4" exaust. Issopro fuel pressure gauge.
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post #2 of 10 (permalink) Old 09-11-2010, 04:52 AM
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could be a solenoid that actuates it or have you tried the APPS mod to see if that might work for ya?

2000 Ford F650 - CAT 3126
1999 International 4700 - DT466E
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post #3 of 10 (permalink) Old 09-12-2010, 03:01 PM Thread Starter
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I did have to replace one solenoid last year that was causing the truck to hang in 2nd gear and that fixed that problem. What APPS mod are you refering to try?

2001 Dodge ram 2500 auto 4x4 cummins. 4.10 gears, 285 tires. Superchip, CFM+ intake, K&N air filter, 4" exaust. Issopro fuel pressure gauge.
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post #4 of 10 (permalink) Old 09-12-2010, 05:13 PM
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post #5 of 10 (permalink) Old 09-12-2010, 07:56 PM
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That is about 1500 rpms in 4th or 2400 in 3rd?

That sounds like it is at a shift point and will go back and forth depending on load and throttle position. You may need the dealership to re flash your tcm.
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post #6 of 10 (permalink) Old 09-12-2010, 08:29 PM Thread Starter
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Thanks for the advice. I am not exactly sure the rpm but I check. I know its always right at 35 mph when it will switch back and fourth from 3rd to 4th.

2001 Dodge ram 2500 auto 4x4 cummins. 4.10 gears, 285 tires. Superchip, CFM+ intake, K&N air filter, 4" exaust. Issopro fuel pressure gauge.
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post #7 of 10 (permalink) Old 09-13-2010, 04:37 AM
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Quote:
Originally Posted by later View Post
That is about 1500 rpms in 4th or 2400 in 3rd?

That sounds like it is at a shift point and will go back and forth depending on load and throttle position. You may need the dealership to re flash your tcm.
35 is way too low for that shift. I come up with 1008RPM in 4th and 1460, in third which is about right. In my truck, I keep O/D turned off until 55mph anyways, so its never been an issue. But in the rare occasion that I forget to turn O/D off, it goes in around 45mph. It could be output speed sensor in the trans. That shift is controlled by a solenoid and is triggered by the PCM based on a couple variables, those being speed, throttle position. So I would start looking there.
Sean

2000 2500 reg. cab 4x4 auto 577hp
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post #8 of 10 (permalink) Old 09-14-2010, 04:11 PM
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Ok, let me check my math,
1600 rpms and 4th is 1 to 1 so divide by 4.1 the rear end ratio = 390 rpm of the tires with a stock diameter of 30.8 inches times Pie 3.14 divided by 12 to convert to feet per min = 3143 feet per min of vehicle velocity or 3143/5280 X 60 min = 35.71 MPH in 4th @ 1600 with the TC locked so where is my math off?
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post #9 of 10 (permalink) Old 09-14-2010, 11:28 PM
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4th is .69:1 in the auto and 3rd is 1:1.

I am also assuming a tire diameter of 33" since he is running 285's which are generally a 285/75/16 in these trucks which is actually like 32.8 depending on the tire.
Sean

2000 2500 reg. cab 4x4 auto 577hp
09 6.7L QC LB stick, 4x4.

TOTAL PERFORMANCE DIESEL 707-545-FUEL (3835)
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post #10 of 10 (permalink) Old 09-15-2010, 02:18 AM
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Quote:
Originally Posted by sstockton View Post
4th is .69:1 in the auto and 3rd is 1:1.

I am also assuming a tire diameter of 33" since he is running 285's which are generally a 285/75/16 in these trucks which is actually like 32.8 depending on the tire.
Sean
I think you may have a point, almost OD is .72 and factory size for the tires is 245 or 265 but many people to go larger.
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