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Hesitation and Jumping - Transmission Or Not?

Transmission Fluid Flush

In our Ask a Mechanic section, user janeti asked the following question:

When I start from a full stop, or in slow traffic my car hesitates to go. When I push on the gas, it doesn't shift quickly into any of the low gears. Once it gets past 40 mph it is fine. It's very slow to get into the lower gears and feels as if it will stall out. It isa 95 lumina. The fuel pump was replaced 2 years ago. It idles fine - not rough.

The immediate assumption most would make is that this is a transmission problem. In a 1995 Chevrolet Lumina, that is not a bad assumption given the age and mechanical history of that model. Given the problem, one of the easiest things to check first is transmission fluid levels. If the trans fluid is low or dirty, that could be the problem - even if it isn't, it's something to be fixed immediately anyway.

However, jumping to the transmission and getting into time-consuming or costly repairs is not a good idea at this point. First, we should rule out other issues that could be the culprit.

Always ready with an answer, Big Block 409 suggests that the problem could actually lie in the engine:

First thing is to know and understand is that alot of times what APPEARS to be a transmission problem is REALLY an ENGINE PROBLEM.

(You said) No check engine light on.

IGNORE the check engine light. In other words DO a scan for error codes EVEN if the light is OFF. If a code (or codes) are present, then post them so we can see them.

THOROUGHLY clean out the throttle-body, (with a quality) throttle-body cleaner paying particular CLOSE attention to the PIVOT points of the "Butterfly".

Clean the MAF sensor with "CRC MAF CLEANER" ONLY.

RULE OUT:

Cylinder misfires
Ignition misfires
Vacuum leaks

He then suggests pulling the engine codes manually, which can be done by any DIY mechanic for free, using the information found at Extreme-Check-Engine-Light-Codes and OBD-Codes. If there is a problem in the engine rather than the transmission, there will likely be a code thrown that is at least alerting to the issue.

Janeti then says that the engine computer is reporting two codes: a "Trans Range Switch Error" and a "TCC Enable Fault (QDM)". She also reports that the car shifts differently when the engine is cold versus hot. At speed (over 45mph), it has no issues - likely because it's reached its top gear.

This means the problem is not the engine, but is almost definitely in the transmission. The fix? Probably a bad TCC solenoid or fluid that's lost its viscosity. The remedy is to drain the fluid, clear or replace the filter(s) and screen, replace that TCC solenoid, and then put everything back together and refill with new transmission fluid. Clear the codes and try it again.

Many vehicles with an automatic transmission, especially those from General Motors, will have similar problems when they age. It is a fact of life when dealing with a very old automobile.