Frequently Asked Questions Associated With The Dodge Cummins Automatic Transmission

 

      Question: Why does my Dodge Cummins Diesel shift so early at light throttle?

           Answer:    Early minimum throttle up shifts are a common complaint on 1996-98 47RE transmissions. 
          The factory minimum throttle 1-2 up shift occurs at aprox 4 mph and the 2-3 at 9 mph.

Preferred 1-2 should occur @ 8-10 mph and the 2-3 @ 15-17 mph, at minimum throttle.

New TRANSBUDDY shift springs allow the minimum throttle 1-2 and 2-3 shift to be calibrated to the correct mph. Only install shift springs if up shifts are too early during initial road test.

Note: Some late 1999 and most 2000 and later models shift on time and do not need new shift springs.

Do not install shift springs on 1994-95 47RH unless necessary.

Early 47RE models 96-98 governor curves vary from vehicle to vehicle so there is no set rule on minimum throttle up shifts. This requires an initial road test. Page 6 of main instruction sheet lists mph values on both the new inner and new outer 2-3 shift springs for calibrating the shift timing.

If a 47RE shifts early even with the new TRANSBUDDY shift springs, (mostly 96-98 models) check desired governor pressure with a snap-on scanner and compare the reading to actual governor pressure. A minimum throttle 1-2 should occur at about 10 mph with aprox 10-12 psi governor pressure. The 2-3 minimum throttle upshift should occur at 15-17 mph with around 20-25 psi governor pressure. If the desired governor pressure is rising too quickly which is often the case, it will cause early shifts and is usually a defective computer.


Question: What should my idle pressure be and at what rpm should my trans shift at wide open throttle?

Answer:   Hook a 300psi gauge to the accumulator port on passenger side of case. Minimum line hot in "D" should be 95 psi idle and 165 psi at wide open throttle. Pressure readings will read 5-10 psi higher when cold. The W.O.T shifts will be 2500-2650 rpm's for 12 valve and 3000-3100 rpm's for 24 valve. These pressure readings are for single plate torque converters only. Multi plate converters may run lower pressure.


Question: Why did the rear band burn up during initial road test right after TRANSBUDDY installation?

Answer: The reverse circuit is very sensitive to cross leaks resulting in rear band burnup. This can be eliminated by following the instructions in TRANSBUDDY Kit. Very expensive! To check, hook a pressure gauge to the rear servo at start up. Pressure should be zero at rear servo except in reverse and manual low. If pressure exists during upshifts, remove valve body and realign separator plate to channel casting. See page 2. Holes "L".


Question:  Why does the 2-3 shift feel so aggressive or firm with other after market torque converters and valve body calibrations?

Answer:   Dunrites' TransBuddy valve body kit fixes incorrect shift timing and eliminates firm aggressive 2-3 shifts. Note: Always check front band servo apply lever ratio. It is marked on the side of the lever. If the ratio is not marked or is higher than 3.8, change it. The 3.8 lever can be purchased from a Dodge dealer P/N 2125067. 48RE trans. Come with a 5.0 lever. Please change to 3.8. Adjusting the TV cable to cover up internal problems will likely produce a 2-3 flare up. For the optimum shift feel and adjust-ability, read page one of main TransButtty instruction sheet.

Question: Why does my transmission have a delayed N-D engagement after shut down or early morning starts?

Answer:  If complaint occurs after overnight shut down, it indicates that the converter is draining back into the pan. To Qualify: Pull the trans dip stick before startin the engine. Is the level above full by 3 to 4 inches? If yes we have drain back. Now: if the truck is parked for days or weeks, consider this normal. If thi occurs over night, something is wrong. Below are the most common causes.
  1. Front pump bushing to torque converter hub has excessive clearance.
  2. Front cooler line check ball has been removed or is defective. (It's in the rubber hose at the heat exchanger).
  3. If this happens right after trans work, suspect something in the valve body.

 
Question: Why does my transmission fail to engage torque converter lockup?

Answer: Factory Switch valve may be sticking due to drilling burr, or valve body bore needs cleaning.  If this valve sticks, vehicle will not move or take 2 to 3 minutes to fill the converter, and/or no lockup. Note: When valve is inboard, converter is unlocked. If valve is sticky when VB is assembled, make a paste out of Ajax and cleaning solvent or diesel fuel. Use this paste on the valve, install valve into VB bore and spin with a piece of vacuum hose by hand until valve moves freely. Valve can be air tested both on the bench and in the vehicle by blowing in the exhaust slot at the  T.C.C. apply valve. See “Air Check Here” below.



Question: Why does my truck seem to have no power during take off?

Answer:   After overhaul this trans makes quite a bit of break in metal. Don't be surprised if after road test the governor solenoid sticks. This causes wrong gear starts, shuttle shifts (bang bang bang) at W.O.T., late shifts into third at hard or max throttle. During overhaul, use gray coated planetary washers instead of brass.

Sticky Governor Solenoid Codes: (Snap On Scanner)

P1762 Gov pressure offset,

P1757 Gov zero pressure malfunction.

P1763 Gov pressure high.

P1764 Gov pressure low.

Code 1693 MIL With Companion Module: means there is a problem with the engine computer (ECM). So clear this code first if trans codes will not erase or fix the problem indicated by the ECM.

Qualify if Governor Solenoid is the problem: 47RE Trans.

Use a scan tool hooked to the diagnostic connector or a pressure gauge to the right rear corner of trans case. Notice Governor pressure at 40-45 mph. It must be over 50 psi. If it's not, suspect the governor solenoid sticking.

Here's how to fix it:

  • With pocket screw driver, bend back the four tabs on solenoid can. See Fig. 1.

  • Careful: When can is separated from the aluminum housing (part with the screen), a tiny check ball falls out. So do this over a shop towel.

  • Using two shop towels, break the flutes off a .055" drill bit and use the smooth end as a punch to knock out the brass washer on the outboard end of Alum housing. See Fig 2.

  • Stick the screen end into a deep well 5/8" socket and using a hard metal surface (sprag race) place drill bit on sprag race and rap socket with a small hammer until inner valve knocks out the brass washer on outboard end. The brass washer, tapered spring and valve will fall into the deep well socket.

  • Make a paste out of Ajax and cleaning solvent and lap valve in bore until free. Clean all parts and install valve in bore with brass bushing end first, large end of spring on top of valve and then brass washer.

  • Use arbor press to crimp washer in place. Fig. 4.

  • Use small paperclip to push valve toward spring to check for sticking after cleaning Fig. 5.

  • Fig. 6 shows exploded view of internal parts of solenoid housing.