Helping someone on their 94’ c1500 305 tbi truck with 4L60 figuring out if we should just swap out with all new shift solenoid kit
Or can an engine VSS, TPS, MAF, MAP sensor cause problems to?
94’ has no tachometer so it’s hard to visually determine the shift pattern unless you just go by feel.. to me it shifts 1-2 then 4 but he thinks it’s 1st to 3rd skips 2nd . Never slips never drops out of a gear either…
The truck is obd1 no trans codes
I feel like the 3rd shift pattern by feel really drops the ball with torque that’s why I say 1-2 then 4th
I dunno I once had Limp mode issue on my 94 suburban and I fixed it with a whole new solenoid kit
Might be far fetched but any truth with any particular engine Sensors known to affect
2-3 shift on a tbi 305 4l60 trans
93-94’ year span
You/he needs to rule in or out problems with those engine management sensors before doing anything with the transmission. If either of you have a TECH 1 or equivalent bi-directional scan tool that's capable of rendering OBD-1 data streams from the ECM, plug that in, take for a test drive and verify what's happening. If not, use a multimeter to test the suspect sensor(s) for those that can be tested via a DVOM (search youtube for videos covering the test procedures those sensors)
You can also rule in or out issues with third gear itself (3-4 clutch pack) by simply unplugging the transmission's large case connector on the pass side of the unit, starting the truck up and putting it in drive...It will default to third gear. If the truck moves on it's own, or with a little bit of throttle then the 3-4 clutch and forward clutch packs are both working fine. If you're able to achieve 2nd gear then the band is likely fine. The only way to obtain 2nd (and 4th) is via the servo applying the band which then 'brakes' the reverse input drum, arresting it's rotation.
Shift solenoids A & B are both off in third gear...Shift Sol A is on in 1st and 4th, off in 2nd and 3rd. Shift Sol B is on in 1st and 2nd, off in 3rd and 4th...So if you had a shift solenoid problem, you'd be missing more than just 3rd gear. You may have a failed 3-2 control solenoid, which I have seen cause downshift issues into 2nd or upshift into 3rd so it's worth considering...You also continuity-test each solenoid via the case connector on the trans.
ETA: a bad VSS will present as a no-upshift from first gear condition.
Here's an image of the pins you can use for testing do you can test each solenoid without dropping the pan. You also test the pressure switch manifold as well, to rule it in our out as a cause or contributor to your problem.
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The only other possibility is a stuck or jammed 2-3 shift valve or 2-3 shuttle valve in the valve body; these are located in the valve train at the shift solenoid B location. I've actually never seen one come in with a jammed/seized 2-3 shift or 2-3 shuttle valve and been rebuilding these transmissions for over 10 years.
