Hot Rods Deuce Pickup Transmission Problems?

Drive my deuce pickup every day. Lately I've noticed the turbo 350 trans is shifting a little different. Seems like the duration between shifts is longer and shift speed has increased. Sometimes unless I want it to wind tighter I have to pull the shifter into 2nd then back to drive for the up shift. Trans doesn't slip, no leaks, doesn't hesitate when it's put in gear and seems just fine going down the road. Has a large in line cooler getting plenty of air flow.. It has probably 60K on it. Has about 3k since a filter change. Also fluid level is tough to check, it's got one of those worthless Lokar short dip sticks. I'm confident it's not low on fluid. I'm no trany guy. Suggestions? Thanks

 

Vaccum modulator? Maybe first off check the pipe to it is in one piece with no leaks.

 

Check the govenor

 

I will second checking the modulator and add the vacuum line between it and the carb. I once ran an all rubber line and discovered cracks (aka leaks) causing shifting issues. I converted it to steel line with small lengths of rubber line at the connections.

 

Mine was doing similar. The modified dip stick was marked wrong. Low on fluid. I modified the dip stick. Trans shop added about a 1/4 to my full mark.

 

I'm back. Had an appointment at the local repair shop for Tuesday. They said driving shouldn't be a problem as long as I can shift it manually. I'm headed north up the 4 lane about 30 miles from the shop running about 70 and all of a sudden I lose everything. Trans is coasting. I had a good head of speed so I coasted to the back lot out of the way at the truck stop. I try the truck in all 3 speeds and reverse and it just sits there. I am thinking the trans went south. Call my wife, she comes and rescues me so I can get the car trailer. I back up to the truck, drop the ramp, try the truck and it drives up into the trailer like nothing happened. Reverse also works? I've noticed the truck puffing some smoke recently and when I checked the oil a few days ago it was black. I've heard of the modulator going bad and the engine vacuum sucking the transmission dry and burning the trans fluid thru the motor. It's a mystery?

 

I think I'd try a different trans shop.

 

I had a bad choice of words. This repair shop had nothing to do with this transmission, it was rebuilt in KC when Howard built the truck. They never have laid hands on this truck. I'm not one to point blame. It'll all work out.

 

Auto's have three things that affect shift times, road speed (governor), manifold vacuum (modulator) and throttle pressure (TV /kick down linkage). try vacuum leaks and TV adjustment first as they are the easiest and cheapest to check. JW

 

Will do those Monday. I not much of a mechanic but how do you adjust the throttle pressure with the TV cable on a 350 trans other than when it kicks into passing?

 

If the smoke is white you probably have a leaking vacuum modulator. Pull the vacuum line at the engine, stick a small screwdriver down it, pull it out and check if it has fluid on it.

 

Sounds like an easy way to diagnose.

 

I agree with checking the modulator. Even just replace it, they're easy access and fairly low cost item. If the vacuum line has oil in it, that indicates modulator leaking. That could also affect shift points. Be sure to check fluid level and top off to ensure it's full. I bet it's low.

 

A bad modulator will not affect it going into gear or reverse. You got other problems.

 

Correct but will effect shifting there on due to false vacuum at the modulator, the only thing that will effect going into reverse or low when stopped is the shifter. JW

 

Speculating ain't gonna fix it.
Going to have to get under it.

Kickdown cable adjustment or stuck, can affect upshifts, but wont create no movement.

I will agree that the Locar dipstick is tough to read fluid level at best, let alone if it's even the correct length.
Fluid level hot should be roughly at the pan rail.

Pull the vacuum line off of the modulator and see if there is fluid in the line. If there is, your loosing fluid in the trans.
A bad modulator can cause automatic upshifting issues.

I would also take the pan off and inspect.
You can then also check the accuracy of the marks on the dip stick.

There is a real possibility it's low on fluid.

One common problem back in the day, was the filter would come loose and fall off the valvebody.
Combine that with the possibility of low fluid level and the result, would be, the trans would neutral out.
Let it sit a while and the converter would drain back somewhat and move again for a short time.

Bill

 

On a 350 the vacuum modulator controls throttle pressure and transmission operating pressure. The cable is only for kickdown.

 

Justpassingthru: Your last paragraph was exactly what happened yesterday. The trans nuetraled out so I coasted into the truck stop and by the time I got home to get the trailer and returned ( hour and a half ) I started the truck and drove into the trailer as if nothing happened. I don't know about the filter yet.

 

I'd go with what Justpassinthrou said rather than the guessers. My bet is on the modulator and a low fluid level.
several years and 80 K miles of driving my 51 Merc with a 350R Olds and a turbo 350 without the tv cable aka kick down cable connected says that they don't have much to do except hold the trans in gear a while longer under acceleration or kick it down a notch when you kick it. Nothing like the 700R4 where the adjustment is critical.

 

I took the truck to my go to guys with a lift that have been doing the updating on the truck since I got it. It backed right out of the trailer and drove into the shop? They're going to pull the pan just for a look. The pan should be clean as they just had it off about 3500 miles ago for a filter change. If it's got stuff in the bottom that's not good. We'll see. When the trans quit at about 70mph I put it in neutral and coasted into the truck stop and got out of the way.

 

Torque converter splines are stripped.

 

Striped splines? I've never heard of that. If they were striped would the vehicle still be able to move as it dud today?

 

It’s never happened to me, but I wouldn’t think so.

 

I worked in a mazda dealership that we had some cars towed in that stop moving, after towing them to the shop we would get in and test drive them,we took the trans apart on a couple but found no thing,then it happen again with a different car,same thing still found nothing,a local tran guy came over with a input shaft and found some spline would slip after turning it for a while.

 

No.

 

If they locked up

 

It was the modulator, sucked the fluid down to a couple quarts.. Bottom of the pan is clean, No visible damage. We'll try a new modulator, new filter, fresh fluid and see what happens. Might get lucky?

 

Wait! So most of the trans fluid got sucked into the engine and burned off???

 

Transmission had no leaks or other signs of fluid leaving, that's about the only place it could have went? I noticed some smoke for the last couple weeks. Checked the engine oil, it looked good. Also processing that much trany fluid thru the motor makes me wonder how much damage that did to the motor. You have any other theories? .