crwdns2936637:0crwdne2936637:0 crwdns2853008:0crwdne2853008:0 crwdns2861143:0crwdne2861143:0

Repair guides and support for C/K pickup trucks sold by General Motors under the GMC brand, including the GMC Sierra.

crwdns2934591:077crwdne2934591:0 crwdns2934593:0crwdne2934593:0

crwdns2933897:0crwdne2933897:0

started running poorly a few days ago

My 89 GMC sierra does not have a vacuum modulator valve,it started running like crap a few days ago and shifting from first to second,it slams,shifts hard going into second. Why?

crwdns2934081:0crwdne2934081:0 crwdns2934083:0crwdne2934083:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0

crwdns2933313:01crwdne2933313:0

crwdns2934221:0crwdne2934221:0
crwdns2931211:0crwdne2931211:0 crwdns2931215:0crwdne2931215:0 crwdns2934225:0crwdne2934225:0
crwdns2934051:0crwdne2934051:0

crwdns2933897:0crwdne2933897:0

I would take it to an AutoZone and get a free computer read out so you have even an idea of where to start looking.

crwdns2934105:0crwdne2934105:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 1
crwdns2934285:0crwdne2934285:0

crwdns2934229:0crwdne2934229:0

Gary Seely crwdns2934231:0crwdne2934231:0
crwdns2936625:0crwdne2936625:0:

crwdns2936751:024crwdne2936751:0 0

crwdns2936753:07crwdne2936753:0 0

crwdns2936753:030crwdne2936753:0 4

crwdns2942667:0crwdne2942667:0 51