Question about 1991 GMC C1500
I have a 91 GMC Sierra 1500. Original 5.7L motor with no problems. I have just went through my 6th transmission, 5 of them being the 700r4 and this last one being a 350 turbo from a 74 Chevrolet pickup. All of the 700r4's do the same thing and go bad within a mile. They will shift all the way through maybe one time and then after downshifting they only have 1st and 2nd and then pops into what seems like neutral, and reverse works. Ive tried new ones, used ones, rebuilt ones, ive put a new computer in it, new radiator with trans cooler, new detent cable and had the dealership dial it in and they couldnt figure out why it wouldnt shift into 3rd..had 2 or 3 local shops look at it and none could give me an answer. I just recently put the 350 turbo longshaft in it with only having to run a vacuum line and move my crossmember a few inches up and it would work perfect until it drives a little bit and gets warm then it shakes when starting off from stop sign or redlight or something, maybe this one is going bad i tried it as a last resort and it worked for a few months. The truck was given to me from my father who was the only owner and took excellent care of it and i wont get rid of it and i wont to get it driving. If anybody has ran into a problem like this or can help with any advice i'd greatly appreciate it. -Ryan
Just rebuilt700r4 transmission and it is sliping in reverse what can cause this.
Posted on Apr 11, 2010
I went thru the same problem years ago. When the 700R trans grinds itself up, all the stuff get into the trans cooler. It is located in the radiator. This needs to be flushed, preferably by a good rad shop. If not the junk in the cooler gets in the rebuilt trans. clogs the filter and burns it up.
Posted on May 08, 2010
Stay with the 350 sounds like your slip yoke is wore out
Posted on Jun 25, 2009
Stick with the 350 or a 400, buy a heavy duty unit from SUMMIT RACING PARTS, they are on the internet, they are sometimes cheaper than having yours rebuilt, on the 350 or 400 that is for sure, and far superior, also they can supply the gear set at a fraction of the dealer cost, remember u need a 3.08 gear set. 700R4's have been a problem from day one, I worked for a GM truck dealer, lost count of the number we removed that were still in warranty, GM could not supply the rebuilds fast enough, every one was slated as the new revised design, end result junky design, they finally abonded it and cam out with a new transmission design.
Posted on Dec 11, 2008
Try using a t5 transmission. I have a sport 1500 chevy that originally had a 305 and later had dropped a 350 bored over .40 and the transmission has not messed up one bit. the t5 is a 5 speed transmission and im sure you know how to drive stick so give that a shot. If it doesnt work just write me and let me know. firstname.lastname@example.org thanks
Posted on Apr 15, 2009
a 6ya Mechanic can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repair professionals here in the US.
click here to Talk to a Mechanic (only for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
Jan 26, 2016 | GMC Cars & Trucks
Nov 16, 2013 | GMC Cars & Trucks
Oct 26, 2012 | 1997 GMC Sierra K2500
Aug 20, 2011 | GMC Sierra 2500HD Cars & Trucks
May 13, 2010 | 1989 GMC Sierra
Feb 23, 2010 | 1989 GMC Sierra
Jan 10, 2010 | 1996 GMC Sonoma
Nov 20, 2008 | 1989 GMC Sierra
Oct 27, 2008 | 1993 GMC Sierra
9,273 people viewed this question
Usually answered in minutes!
Step 2: Please assign your manual to a product: