oneshot

Hey Guys,

I have a 77 vette that I put a B&M TH350 transmission in. The problem I am having is when the car is cold. I have to let it run for a long time before it will shift out of park into any gear. This does it when ever the car is started for the first time. I can run through all the gears and it will not engage into any of them. I run the car at 1500 rpms for a good 5 or 10 minutes then it will shift. It jerks the car alot when it first shifts but it will finally go. Now when I get it going, I have no problem shifting at all. It shifts just like normal. This only happens when the car has been sitting for a while.

I checked the transmission cooling lines and they are not blocked or colapsed.

Any ideas.

oneshot

Ok, it might be the vacuum module. I did some more research and kind sounds right. I have a pretty big cam in the car and very low vacuum. Less then 10Hg. So next question is I have read about getting a vacuum modulator that will work for cars with low vacuum but I can not find a type or part number. Has anyone seen this before?

7T1vette

Your problem is not the vacuum modulator. You either have low oil level (until the oil is hot enough to expand and keep the pump from sucking air) or you have a sump intake problem. Auto tranny oil level is checked [and set] with engine running, not shut down.

oneshot

Thanks, I will double check the oil level but I am pretty sure it is at the correct level.

If it is full then what can I do to check the sump intake? or do you mean pump intake?

Thanks
Aaron

7T1vette

Pump intake...sump intake...no difference; just semantics. Just drop the pan and check the pick-up tube for any problems with proper sealing: crack in the tube; loose/cut/hard sealring on the pickup tube; broken/cracked transfer tube from pump to block. It could also be a problem with the pressure regultor spring system in the oil pump. Either way, your problem should be in the engine sump area (if the tranny oil level is correct.) You haven't changed/replaced the tranny dipstick for any reason, have you?

RonR80

I'd check the level first if it's not up-shifting try or check the modulator vaccum line , you can get adjustable modulator if need be. You can change a modulator valve in ten minutes. Ron

oneshot

nope, same out dipstick. I did add a extra deep pan. It came with an extension for the filter to set lower in the pan.

Thanks
Aaron

7T1vette

The pan wouldn't change the oil level requirement. Got to be oil level, suction tube, or pump problem [with the symptoms you described]. Add 1/2 quart of tranny oil and see if you get any change. 1/2 quart too much won't hurt anything. It may not fix it, but if it changes for the better, that's your problem.

oneshot

Will do. I will report tomorrow if it changed anything.

Thanks
Aaron

vetteboy101

Mine was doing the exact same thing after I installed my crate motor. It was the darndest thing. I looked under the car and the vacuum hose had come loose from the modulator. I had to get some new hose and a small clamp and fixed the problem. Mine would take forever to shift gears. I have the TH400.

7T1vette

A bad modulator [or disconnected vacuum line] will cause "late" upshifts; but it will not prevent the tranny from engaging its clutches. Not the modulator.