Automatic slipping, flaring or refusing to shift

A buyer's guide for this generation puts the automatic's problem down to heat: towing, old fluid, a clogged cooler and high temperatures shorten its life, and the guide tells a buyer to look for smooth shifts and clean fluid as the test. Owner reports filed with the United States road safety agency add the specific complaints that show up first — a transmission that will not shift properly when the truck is cold, and torque converters that failed. Heat is the whole story here and it explains why the symptoms arrive in the order they do. Transmission fluid does not wear out gradually and evenly; it survives until it has been cooked, and then it stops doing the two jobs it has, which are carrying pressure and holding friction. Once the fluid has gone, what it destroys is the clutch material inside, and that is the part that turns a fluid service into a rebuild. So the useful judgement is not about the transmission — it is about time. A truck that is slipping today can often be saved with a service; the same truck a thousand kilometres later usually cannot. Drive it gently, keep it off towing and long climbs, and get the fluid looked at this week rather than at the next service.

Gen 2Gen 2.51991–1999Damages other partsCommunity consensus

Drive gently — repair soonManeje con cuidado — repare pronto

Community consensus. This entry is not backed by factory documentation — treat its values and steps as a starting point, not as if they came from the factory manual.

Consenso de la comunidad. Esta entrada no se apoya en documentación de fábrica — tome los valores y los pasos como punto de partida, no como si vinieran del manual de fábrica.

Symptoms

It will not shift properly until the truck has warmed up
The engine revs rise between gears, and the truck does not gather speed with them
A shudder or a fine vibration at a steady cruise that goes away when you touch the throttle
The fluid on the dipstick is dark brown and smells burnt
A harsh bang into gear where it used to be smooth

Likely causes

Burnt or long-overdue transmission fluid
Blocked or restricted cooler circuit
Clutch packs worn out by heat
Failing torque converter, or its lock-up clutch

Diagnostic steps

With the engine warm and running, check the fluid level the way the truck expects and wipe the dipstick on white paper to judge its colour and smellPoints toBurnt or long-overdue transmission fluid · Clutch packs worn out by heatRules outBlocked or restricted cooler circuit
Note whether the trouble is worst cold and improves as it warms, or worst hot after a long runPoints toBurnt or long-overdue transmission fluidRules outFailing torque converter, or its lock-up clutch
Have the cooler return line disconnected into a container and the flow checked while the engine idles, which shows whether the circuit is restrictedPoints toBlocked or restricted cooler circuitRules outBurnt or long-overdue transmission fluid
At a steady cruise on a level road, hold a light throttle and feel for a fine shudder, then lift slightly and see whether it disappearsPoints toFailing torque converter, or its lock-up clutchRules outClutch packs worn out by heat
Drop the pan and look at the magnet and the bottom: fine grey paste is normal wear, dark friction material and metal flakes are notPoints toClutch packs worn out by heatRules outBlocked or restricted cooler circuit

Fix paths

Service the fluid and filter, and keep servicing it

$–$$Difficulty 3/5

The cheapest useful action and the only preventive one. Use the fluid specification the truck calls for rather than a universal product, change the filter with it, and set a shorter interval than the book's if the truck tows or climbs. On a transmission that is already slipping badly this may not save it, and it is still the right first move.

Clear the cooler circuit, or improve it

$$Difficulty 3/5

A restricted cooler means the fluid never gets cool no matter how new it is. Flush the lines and the cooler, and if the truck tows or works in heat, an additional cooler is the change that actually addresses the cause the cited guide names.

Rebuild or replace the transmission

$$$–$$$$Difficulty 5/5

Where the clutch material is already in the pan or the converter has failed, fluid will not bring it back. Have the cooler circuit cleaned out as part of the job, whatever else is done — a rebuilt transmission fed by a cooler full of the old one's debris does not last.