so i posted a few months ago that my truck would not back up unless it warmed up for a while and I would have to get off the gas for it to shift from first to second and it wouldn't go to third at all. so the conclusion in this forum was change or rebuild. changed transmission reverse seems to work fine but still wont shift to second or third. so the question is vacuum pump? I pulled the pump already and put my finger on the valve and spun it and it did suction to my finger. so the one thing I am most concerned about is I didn't change the torque converter could that be the problem?
info 1987 f350 dully with an automatic c6
thanks
update: drove truck without vacuum pump no change in shifting reverse worked fine brakes no good. so what do u think, torque converter or something else?

 

I just read your previous transmission topic.

It seems clear to me that your problem is with the Vacuum Regulator Valve, aka 'VRV' which controls your C6 shifting by regulating the level of vacuum to the transmission. The VRV is adjustable through a broad range but the right spot for proper shifting with an old and worn VRV is going to be a very fine line, if it is not completely worn out - in which case it will have to be taken apart and "fixed" but you need to have skills and patience to do this.

Adjustment is not a simple adjustment - it requires a hand vacuum pump with a vacuum gauge, about $38.00?? at a parts store and VERY CAREFUL ATTENTION to following the adjustment procedure instructions EXACTLY.

I have to leave right now and I won't be back until late so that's all I can help you with at the moment. Do some searches on this forum for 'VRV' or 'VRV Adjustment' and read up on it! Read a LOT because this is what you will be dealing with.

Also if your old parts truck still has the VRV you had better keep it and protect it because you may need it! You can't buy new ones but old ones CAN be fixed.

That's all I have time for right now (I'm already running a half hour late) so read up on the VRV so you'll know what you will be dealing with.

 

Hey thanks for the info. I will get right on that. Just one question if I by some miracle get my hands on a new one can I just slap it on and it's good to go or are there adjustments that have to be done even with a new one?

 

If you've looked, by now you know they are not available new or rebuilt.

I don't own a vacuum pump/gauge so I adjusted mine after an injector pump change with no real issues. Loosen the two screws (right angle philips ie Chapman), bump forward for higher/crisper shifts, bump toward the back for lower/smoother shifts. Took a few tries but not a worrisome thing. Wished I'd known this a couple decades ago as I was never particularly fond of the C6 in my old Bronco but apparently it was all in this adjustment.

Good luck,
- Jeff

 

The quick and correct answer is that a new one would require adjustment. I will come back to this question a bit later and add some options as well as a lot of additional information about the VRV itself.

HOWEVER, before we even consider adjusting or changing the VRV there are OTHER things that you need to CHECK FIRST.

Mainly that will be the all of the vacuum lines and their connections associated with controlling the shifting of the transmission. You may as well check all vacuum lines and their connection points (where leaks are usually found) while you are at it because vacuum leaks can affect any component that is controlled by vacuum including transmission shifting.

I want to address this in more detail in my next post which should be posted shortly.

 

For the moment we can only ASSUME that the Vacuum Pump itself is in good condition and is pulling a full vacuum in the system within specifications. You cannot confirm this with your finger, you have to use a vacuum gauge while the truck is running at idle and I do this by removing the vacuum hose at the Power Brake Booster and checking the vacuum at that location. I'd have to check again to confirm this but I think that the minimum acceptable vacuum is 22 in.Hg (Inches of mercury) shown on the gauge which is about -74 kpa (kilopascals) if you are using that scale.
If it shows below 22 in. Hg that it could indicate vacuum leaks or a vacuum pump that is beginning to fail.

You can check that later but lets go directly to checking the Vacuum Lines and their connections.

I use the terms 'vacuum line' and 'vacuum hose' interchangeably.

On a vehicle this old it's quite common for rubber vacuum lines to have become dried out, stiff and sometimes cracked or deteriorated where the rubber is stretched over the vacuum hose fitting. When rubber vacuum lines are old, the rubber at that location gets stiff, looses it's elasticity and doesn't grip tightly around the connector so they are prone to leaking even if they are not visibly cracked or deteriorated. Leaks will lower the vacuum in the lines and cause problems (very common in gas engine vehicles). I will often remove an old vacuum line from the connector, cut off the stiff end so the cut end will be soft and pliable and then put it back on the fitting, or I may replace the whole line.

Lets start back at the transmission and move forward. There is a rubber vacuum line connected to the Vacuum Modulator Valve at the back of the transmission. From there it goes toward the engine compartment and connects (under the truck) to a METAL vacuum line which is just a metal section of the same line, a transition piece where it comes close to heat from exhaust pipes). That piece of rubber vacuum hose should be securely clamped at each end. I used two clamps where it goes over the end of the metal vacuum line. This section of rubber hose on an old truck is likely to be covered with old oil, transmission fluid, dirt, grease, etc. and if it looks like that I sure wouldn't trust it, - I would replace it.

It's very unlikely but remotely possible that the metal line is defective, cracked, bent/kinked or corroded through. You would need a hand vacuum pump and gauge to test it so I am going to skip over that.

That metal line comes up behind the engine to a point behind the air cleaner at the back of the engine where another section of rubber line is connected to it and goes to the "OUT" port on the VRV which is the lower connection. BE VERY CAREFUL when disconnecting vacuum hoses from the plastic fittings on vacuum controlled components because if you are not very careful you can break these fittings and then what are you going to do if the component you just broke is officially “obsolete” and no longer available? This is the case with the VRV.

The next rubber vacuum hose to inspect (and repair if necessary) is connected to the “IN” port of VRV which is the TOP connection. That line goes back to a multiple connection vacuum fitting on the firewall, it's actually the distribution point for all of the vacuum lines. The two big hoses that are clamped on = As you are looking at that vacuum connector the large hose on the passenger side comes from the vacuum pump to this vacuum distribution fitting and the large hose on the driver's side goes to the Power Brake Booster.

One of the small lines goes to a vacuum motor that controls the blend door for your heater (it's in the corner above the heater core). You should check all of these vacuum lines and connections. If you have Cruise Control there will be some other lines to follow and inspect. They are all easy to access.

 

So I had already kind of looked over the vacuum lines they all look like they're in pretty good condition everything you said was correct as to where everything was located and going over them they all look to be in relatively good shape. I did adjust of VRV to see if I could get it to shift properly and although it made some difference I had it all the way on the easiest setting to shift, still pretty rough. So I check my donor truck and did have a VRV so I swap them out and after a few adjustments she shifts perfect. Thanks guys I was feeling pretty inadequate for a minute there.