01 duramax

[miamimax]

i was towing a small tralier when my truck slowed downed then it would'nt go passed 65mph.the check engine light came on.the next day the light went out and was able to go passed 65.if i drive it easy it will go through all the gears fine, but once i step on it, it holds third gear for afew seconds then shifts hard... i'm puzzled can someone help???

[DmaxMaverick]

Welcome aboard!

Is your SES (Service Engine Soon) lamp on? If so, you need to get the code(s) read before you'll know the whole story.

Otherwise:

Try replacing fuel and air filters. If the fuel filter is fresh (less than a couple thousand miles), it may be leaking air under load, and needs to be removed and reinstalled correctly. If the filter has more than 1,000 miles on it, it's better to just replace with new. If the problem returns after a few (hundred or thousand) miles, you may have some bad fuel.

Your thread has been moved to the Duramax Forum.

[miamimax]

thank you i will try it and get back to you

[miamimax]

thanks a lot i changed my fuel filter and replaced my air filter and now my truck is shifting like its supposed to...thanks again:)