300sd transmission won't up shift Help

Did you count the shifts?

Starting out from a dead stop in L, is 1st, shifting up to S and immediately BACK to L will hold 2nd, then on to S for 3rd and D for 4th.

My 300SD runs at 3,000 rpm at 65 mph (70 on the speedo).

I believe you have done all the right things to check the installation.

Suggest you disconnect the pressure rod or cable to the throttle linkage to force early up shifts.

There's a problem for sure if it's then unchanged.

I have done that. I have had this car out for several drives, all with the same result. I completely disconnected the pressure rod or cable at one point and no change. There are two shifts, they feel normal and at the right speeds but at about 38 mph I would expect a third shift, that shift never takes place. As you reach 55 the engine is 3000 RPM (way too fast), I have run it up to 3800 or so the engine starts to surge if you push this. At no point can I get it to shift to 4th. Even with a tight pressure rod you would get a shift at some eventual speed I would think. I would think stuck kick down but I think I have eliminated that as the cause. What is bad, I turned down several transmissions over weeks of searching that all wear about $500 and finaly was willing to pay $800 for this one that came from a quite reputable parts supplier and has 98K on it. The transmission looks like the genuine article, is still shinny. It was quite a shock to find it will not provide as good a service as looks good. Well thanks for your thoughts Tom and if you have any others send them over here. Bruce Buchanan

It starts off in second, not first. So, one shift is to get to third, the next one to fourth.

If you hold it in low manually then let it go and shift up you should feel three shifts.

This is all perfectly normal.

I don't know what internal parts trigger the shift to 4th gear. No creative thoughts to add.

Suggest you talk to the yard that sold you this box. I'd suggest willingness to first change / flush the trans oil and filter at THEIR expense (incl. torque converter) as a final attempt to make a success of this box. A failure thereafter is return for a refund - thank you very much (for wasting a lot of my time!)

In fairness to the yard THEY know nothing more about this box than I do

- and that's zero!

So their warranty is a crap shoot; they know some parts will come back but since they haven't invested any labor in installation it's not particularly painful to "eat" a return.

Everything is hydraulic control... so your tranny is bad. Did the tranny part number match? or has a higher last digit? 722.3xx? It cannot be lower number than you have...

I am guessing that it is the wrong tranny... possibly one from those that

Well I checked numbers. Original number 722 303 02 053794 new number is 722 303 02 222285 is said to be out of an 81 300sd. My car is one of those only 85 MPH cars but it used to do 85 quite well.

I just came back from another drive. I hooked up a push button switch to my kick down solenoid and 12 volts so I could energize the kick down any time I wanted, took it for a drive, I found that I can put it back into 1st by pushing the button while pulling away from a stop, and I can put it from 3rd back to 2nd by pushing the button. I figure the kick down system must not be stuck. Tranny just don't like 4th

I will just wait till tomorrow and take it up with the company that sold this to me. My biggest fear is that they will want to refund or exchange the transmission with out a diagnosis and it would be a shame if there was some simple thing that could solve the problem while tranny is still in the car. I will at least see a transmission shop befor I change that box again, I am getting too old for this under the car stuff, though I enjoy it, my neck is still stiff.

Thanks to all who have answered my post, I appreciate you. Bruce Buchanan