Questioni have a 1988 gmc pickup 1500 transmission has not been shifting into high range latly it is a 400 turbo automatic changed vacum module on tranmissiom and checked vacum line to intake manifold all clear on a cold day sometimes it will shift but i cant get it to function all the time what else can i try i have a cruise control that has failed could that be the problem.change transmission because of it and no difference also motor was changed since problem.
AnswerRichard,
Are you the Richard that asked about sending a donation ?.
e-mail me at my below e-mail address and I will explain this boards POLICY as being TOTALLY FREE.
autohelp
Are you POSITIVE that you have the 400 transmission ?. I have rebuilt many transmissions over the years and am now teaching my son as everybody is afraid of the newer electronic transmissions. The ONLY reason I can come up with is that they just don't want to take the time to understand how and what makes the electronic transmissions work.
As for the older transmissions They are very simple and easily modified for any driving conditions.
Back to your transmission. Are you telling me that you REPLACED the transmission and still have the EXACT same problem ?.
Are you POSITIVE that you have the correct sixe inside diameter vacuum line to the modulator and that is is one single length of vacuum rubber line with NO plastic connectors connecting 2 pieces of rubber vacuum line together and has NO other vacuum lines branching off of it ?.
The trans to manifold vacuum line must be one single piece and be the correct inside diameter rubber hose. You CANNOT use a smaller inside diameter rubber hose as you will still have the correct vacuum but the VOLUME of vacuum will be insufficient. A very common overlooked mistake made by many people.
Are you POSITIVE that you have the vacuum line connected to the correct vacuum port on the manifold ?.
Make sure that this vacuum line is not easily pinched shut using your fingers as it tends to get SOFT over the years and does suck itself flat after it gets hot thus restricting the vacuum supply.
Are you POSITIVE that you have the correct modulator as there are different kinds, Some are adjustable and some are NOT. Some are small and some are large. If you have the wrong one and or the one you have is adjustable you may have to adjust it.
What YEAR and MODEL vehicle did you get this replacement transmission from ?.
If you have a DIGITAL camera and can e-mail pictures of the transmission that is in the vehicle please take several of all sides of the trans and e-mail them to me at:
meperganfortis@msn.com
So I can see exactly what setup you have.
autohelp
