I have a 1998 GMC Jimmy and until now we had little to no heat. In the morning when we first leave the house in the cold as we are speeding up we slip into neutral and we either have to pull over or shift the shifter into neutral and back to get it going again. We only notice this happening when it is very cold. How do we fix this before it becomes a bigger problem?
Step one ; check and correct fluid level.
My 79 does this periodically BECAUSE it stays parked so much the seals dry a bit and I need to add a tad once a year at least.
When a transmission starts to do this when it gets cold, the transmission isn’t long for this world.
What usually happens is, as the seals inside the transmission become hard from age they shrink in the cold. This prevents the proper hydraulic pressure from being produced so the transmission can’t shift properly. Then once the temperature warms up or the transmission warms up the seals expand allowing the transmission to shift properly.
If possible when it’s cold, allow the vehicle to idle long enough so the pump/torque converter inside the transmission have a chance to warm up the transmission fluid to prevent the transmission from slipping. Because each time the transmission slips, it’s burning up the clutches inside the transmission.
I would change the fluid and filter to start with. Low temps thicken the fluid and maybe new fluid would help.