94 EXP no O.D. after engine change

[JOHN BUFF]

Thanks in advance for any help.
Last week before I did an engine swap, my tranny worked fine, it was rebuilt by AAmco transmission about 20,000 miles ago (no longer in warrenty).
I replaced my 4.0, and used my original upper intake and all sensors (except the crank sensor), alt, starter and such. Now the tranny will not shift into O.D, all other gears are perfect with no slippage, fluid level is fine, modulator is secure as well as vacuum lines to it (no cracks). When on the highway it's like it is drive, not overdrive. Usually at about 55 mph the rpm's would have gone from 2200 down to 1500.
Any Ideas????????????

 

[MrShorty]

3-4 shift (and torque converter lockup clutch, for that matter) is controlled electronically by the computer.
1st: Make absolutely sure everything got plugged back in.
2nd: Get a wiring diagram and check the 3-4 shift circuit. Run EEC-IV self-test to make sure the computer isn't seeing any problems.
3: Put a voltmeter across the 3-4 shift solenoid and monitor the voltage drop across the solenoid while running EEC-IV output state test. This tests that the computer can switch the solenoid.
4: With the voltmeter hooked up as for 3, do a road test to see if the computer is choosing to shift into 4th gear.
At this point, if you haven't found a problem, then the fault lies in the internal hydraulics/mechanics of the transmission. Because the problem surfaced after installing an engine, I would expect a wire got left unplugged or a wire got cut.

 

[JOHN BUFF]

Thank you for your input regarding my tranny, people like you help the less knowledgable.
Although I did not fully understand what you said, I do agree that more than likely something did not get plugged in all the way, or maybe a wire got pinched.
I tried to think last night , if I did in fact use all of my old sensors. I do know that I did not change the crankshaft position sensor. Also I'm not sure if I aligned the CMP sensor the required 60 degrees, if that makes a difference. I drove the truck today, about 10 miles in DRIVE, and it shifts perfectly.
Once again thank you for your time and info.
John

 

[Flat Top]

no OD

I took my Maf sensor out of the air cleaner box to clean it on my 91 and evidently didn't get the plug all the way back in . Went down the road , no overdrive . Got the plug in all the way and overdrive came back. Don't ask me

 

[JOHN BUFF]

Hello, I have to wait until tuesday to work on the truck again, but I will surely check that out.
Thank you for the reply.

 

[JOHN BUFF]

Thank the lord (and you guys), I now have overdrive and when I tap the brakes at 55mph the rpms go up as the TC unlocks. At 70 mph I'm tacking about 1800 and if I apply the gas, the rpms and speedo rise with each other.
What I did was remove the battery cables for 1 hour, and then drove around the city to rest the VSS, like I said earlier, I changed the TPS and VSS this morning.
THANK ONCE AGAIN.
John

 

[jimbo74]

glad you got it fixed... sounds liek it was a glitch in the computer... and by reseting the computer, it relearned itself correctly while performing its self diagnostic scheck