Cold Shifting?

[motormayhem]

When I start my m1009 in the mornings and begin to drive it doesn't like to shift and winds out the motor. However after about .5 mi it seems to warm up and be fine. Whats up with that? It wasn't doing this until the IP was changed. Oh and the vacuum lines are new.

 

[kipman]

sounds normal, my blazer does not like to be run when cold.

 

[IRWFO]

sounds normal, my blazer does not like to be run when cold.

I wouldn't say it's normal.

 

[LanceRobson]

It's not normal. If you haven't done so, replace the rubber vacuum lines from the vacuum pump through to the transmission. It's take 10-15 minutes and will likely fix the issue. If there is a vacuum leak it will cause late and hard shifting.

If not, look at the -20 manual for the checks to make sure the vacuum pump, modulator etc are working correctly.

If the transmission fluid is old it can cause similar symptoms. So can a transmission starting to die.

The vacuum lines are, if original, over 20 years old. start with the cheapest and easiest fix first.

Lance

 

[motormayhem]

Ok I "tuned" the shift points yesterday afternoon and now the problem is gone.

Thanks,
Miles

 

[LanceRobson]

Good deal!

Lance

 

[IRWFO]

Ok I "tuned" the shift points yesterday afternoon and now the problem is gone.

Thanks,
Miles

How did you Tune the shift points? Do you have an adjustable modulator?

 

[dependable]

If you have not replaced the tranny filter,yet, I would strongly recommend that as well.

 

[motormayhem]

How did you Tune the shift points? Do you have an adjustable modulator?

I adjusted the modulator as well as the valve on the IP.

If you have not replaced the tranny filter,yet, I would strongly recommend that as well.

I did that last week

 

[LanceRobson]

How did you Tune the shift points? Do you have an adjustable modulator?

The -20 TM and a vacuum gauge. the gauge to check the pump and the manual walks you through the process.

Often these trucks had well meaning mechanics adjust the shift points when they should have been replacing $2 worth of vacuum lines. Change them first because of the "you can't see a vacuum leak" deal and the rest is a 10-15 minute job.

Hard shifting is another issue that this will fix.

Lance