Shifting in andn out of overdrive?

[Case500D]

Hi, thanks for all of the help with the exhaust system. I now have another question. My 92 W-250 has a 4 speed automatic transmission. It has been shifting in and out of overdrive between 40 and 50 mph. It will shift up like it is supposed to, but as you accelerate, it drops back down from 4th into 3rd. If I do a full throttle acceleration, it will shift just fine and not kick down. I have had it kick down as high as 55 mph before. The truck actually slows down and the engine revs up. I have serviced the transmission with new fluid and a filter. It mainly does it when it is cold outside. Like today it did it for over 30 minutes and I finally just shut off overdrive and ran in third. The truck has not had many pulling miles, just highway miles. It does shift very nice and solid. Finally it will not act up when I am towing a load over 4,000 pounds. Anyone have any ideas???

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Jeremy Sweeten
1992 Dodge W-250 4x4
Cummins Diesel, intercooled,
LE Package, 165K, AT, Warner Hubs, 3. 54 limited slip differentials, 3" straight pipe, K&N air filter

 

[jsimpson]

Check the connector where it plugs into the transmission. The boot is probably shot and the connectors corroded. Clean them up and graese them up and you should be OK.

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http://coffeewithJesus. homestead.com/web1.html 89 1-ton, Amsoil System 3000 5-30,K&N air filter, cleaned-up exhaust, Dynomax straight-thru, rebuilt pump, thermostatically controlled twin 14" Permacool electric fans, intercooler), modified 518 OD transmission, Gear vendors OD controler, R-134 refrigernt, louvered front fenders, 93 aftermarket smoothie grille, new Dupont Chromacolor black, black-and-red rubber rubstrip, black headlights, powdercoated bumpers; 78 35'Avion, 93 Lance 900 slide in with generator and power jacks. To see my truck, Click on: <A HREF="http://albums.photopoint.com/j/AlbumIndex?u=1169022&a=10097213

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[BushWakr - RIP]

Yup it could be all corroded and not making contact as it should,, or, that evil thing called the throttle position sensor (TPS) is on its way out. I have noticed on mine that there is a threshold setting that makes my transmission behave in a similar manner. If you do a search on the site for TPS you will find several good descriptions of this thing.

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93. 5 D250 4X4,HD Spring Pkg, Rancho 7000's, Rear Swaybar,Dual Shock Front Stabilizer,BD Injectors,31/2" Mandrel bent exhaust,16cm 'Hot End',Modest Pump Tweaks/Timed,K&N Air,Isspro Pyro,Tach,transmission Temp,Auto Meter Oil Filled Boost Ga. , 3:54's, 4 Speed Auto, Clubcab, Aftermarket Reclining Buckets w/ctr Drop Down seat/console, Black over Silver, 21psi,285-65R-16's,American Racing Clear Coat Mags, Amsoil 15W-40HD Marine,12,000 lb. Warn Winch,KC Spots. 97,000 Kms.

 

[Case500D]

Well I have done a search on TPS. It sure sounds like my truck's is going bonkers. Just curious, but where exactly on the injector pump is the TPS? Does anyone have any pictures of where it is and/or what it looks like when you replace one? I am going to try cleaning mine when I can get into the shop (it is 5F right now with a -30F windchill). Thanks for all of the help.



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Jeremy Sweeten
1992 Dodge W-250 4x4
Cummins Diesel, intercooled,
LE Package, 165K, AT, Warner Hubs, 3. 54 limited slip differentials, 3" straight pipe, K&N air filter

 

[paccool]

Sits on top of the pump on a metal bracket. The bracket attaches with 3 of the screws that hold the top pump cover on. ( at least on my 93 thats where its at)

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Stan
93 2WD extended cab, Banks Power Pack, K&N Air Filter, PW Injectors,Auto w/4. 10 rear with limited slip, US Gear Exhaust Brake, 31/2" Exhaust, 5K air bags, Boost/Pyro/Tach Gauges, Green/Silver, new 40-20-40 bucket seats, 149K

[This message has been edited by paccool (edited 12-19-2000). ]

 

[BushWakr - RIP]

Case'
it is located on the 'radiator end' of the injection pump. you will need to look kinda under/around the rad hose to see the adjuster for it. on the top of your inj. pump you will see a raised center with a cap (assuming your cap is still in place), just forward of that is the TPS,it has a 3 wire connector attached to it. I have not had the guts out of one yet. The TPS guts are held down by 3 or 4 screws. Down and underneath is an adjustment for this thing. It is a 10 or 11mm (i think)open end wrench type adjustment.
turning this will change the voltage it supplies which governs 3-4 shift. Counterclockwise increases voltage. mine is kinda stiff which i think is normal. You need to attach a DC voltmeter to the center wire on the connector (there are 3 wires) i think mine is orange, turn on the ignition (do not start) and check the voltage coming out of this lead. It should be around 1 volt. I have found if you increase this it will cause 4th gear to be longer in coming, and if you go to far, it will want to jump around. Just make sure to determine a baseline (what your original voltage is)
These things can be taken apart with some work but its not something i've done.
I am getting an intitial key on voltage of about 3/4 volt right now and i like the shift point that i get from it.
You can find some great pics of the pump, cutaway view here on the site or at one of the perf. sites. Diesel Dynamics i think has some pump pics that are good. if you send me your email i can send you the ones i have as an attachment to an email.
hope i haven't confused you.
regards, bush

 

[preleeguy]

Case, Unless you have a friend in the parts dept at Dodge that will give you a good discount, you need to get your new TPS from Cummins. It will save you some $$$. My son just replaced his this week. He just unbolted it and put the new one on with no adjustment, Works great now,BIG improvement in shifts.
Good Luck,Later.

 

[Case500D]

Thanks everyone for the help. You guys have definitely saved me some $$$. The local Dodge dealer wants $234 for the sensor and $35 for an insulator kit. I will try to find a Cummins dealer if I need a new TPS. I am going to try and clean/readjust mine.

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Jeremy Sweeten
1992 Dodge W-250 4x4
Cummins Diesel, Intercooled,
LE Package, 165K, AT, Warner Hubs, 3. 54 limited slip differentials, 3" straight pipe, K&N air filter
http://home.earthlink.net/~sweeten1/index.htm

 

[Ian]

My TPS is also very touchy. I am probably looking at a replacement before too long. Under 50 mph, any slight power increase and OD drops out. >50 it stays put perfectly.
Price difference between Dodge and Cummins, Cummins just over $C100 cheaper.
Someone else here on TDR suggested poking a small safety pin through the centre wire to the connector to the TPS, then put your pos. meter lead onto it and the neg. lead to ground.
Good luck.

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Ian.

'93 D250 ext. cab. Upgraded injectors, 3. 5" exhaust, K & N filter, Xmsn oil cooler and fan, 4 gauge mount, mirror tubes reversed, RACOR fuel filter, larger transmission oil pan.

[This message has been edited by Ian (edited 12-25-2000). ]