bnrealfast0

1993 Ram 250 CTD: Auto trans. Until the trans. is up to operating temp. driving at 50 mph the trans jumps back and forth from 3rd to OD. It won't stay in OD until almost 60 mph( engines screaming by then)When its warmed up it'll shift to OD between 45 & 50 and stay there. Kick down linkage adjustment seems only to effect first 3 gears and not OD. Any suggestions?

RCW

The 518 used prior to 94, was a 4 speed that has no computer and no lock-up. As a consequence it requires the throttle lever preload adjustment be spot on to allow proper up and down shifting. Based on your description, and my belief you most likely adjusted the throttle lever preload by following the proper procedure, I would suspect your truck has enough miles to warrant a replacement valve body. The valve body can wear too much and then leak off too much transmission fluid pressure to allow the overdrive unit to activate until the transmission heats up and the tolerances close. I would suggest you contact DTT and obtain their replacement valve body.

Den052

The OD is controlled by a electric solenoid in the valve body, 2 wires (one grounded). I have a wiring schematic that I could send to you to show you how simple it is to manually make it shift into OD with a toggle switch.
They have had many problems with the "throttle position sensor". The engine computer looks at throttle position and road speed to decide if the solenoid should be energized. There are many posts on this problem.
Also. I would highly recommend you switch trans fluid from ATF to Penzoil 10W/30 motor oil. ATF dosen't lube properly and causes transmissions to fail too often. I have been using Penzoil motor oil in my automatic for over 5 years and 130,000 miles without a problem. The transmission pan when pulled and inspected has nothing in it whatsoever. It is pristine and pure. (no metal shavings). I really don't need a trans filter because nothing wears. Of course, many people will think I am MAD and CRAZY, however I have worked with automatics for over 30 years and have found ATF to SUCK ROYALLY. It does shift a little crisper though. I call it my "Shift kit in a can" treatment.

RCW

Den053 makes a very good point on the solenoid. Most people have bypassed the automatic solenoid switching circut by now because all the ECS and TPPS do is confuse the thing.

His recommendation on oil is good too. Although, most guys I know now use multipurpose tractor hydraulic oil for AG equipment and industrial transmissions with hydraulic systems, instead of ATF. No wear, and lasts forever. I have it in my 03, and have over 100,000 miles of commercial use with no failures and no "mud" in the pan at service time.

Craig93

Penzoil 10W/30?....if its that good, why doesn't DC recommend it?

Den052

It is basically a discovery by my own experience working with Allison transmissions and everything hydraulic. An Allison transmission has basically the same clutch facings and seals as a small automatic, yet some engineers at Allison back in the 1970's would embrace a C3 or C4 rated oils for use in "heavy duty" service. This included Penzoil 10W/30. I have seen dramatic results with less wear and etc. just by using an alternative oil. Basically trans fluid has not changed since the 1950's. Take a can then and now and you won't visually tell the difference. However, transmission temps have steadily risen to between 200-300 degrees. All I can tell you is from what I have seen and used. Now, Allison recommends their own fluid (which by the way costs about $6.00 a quart), for use in their Allison transmissions. I can achieve the same thing by using alternative oils. I don't have a clue why engineers don't get on the bandwagon. Three reasons that I can think of:
1. You may not like the shift quality as it can be a little firmer in shifting (alternative fluids don't have shift modifiers and tend to grab more). A customer would complain that his transmission shifts too hard.
2. They love the repair bills and the extra money they can make.
3. People are accostomed to seeing a RED fluid called TRANSMISSION FLUID and refuse to put in something that is not RED in color.

All I can say is that I have found my transmission to operate fine with my oils, and the pan remains pristine pure with no clutch wear or metal shavings. People still look at me like they have seen a ghost when they learn I am using MOTOR OIL in a transmission.

bnrealfast0

Thanks for all the suggestions. As far as the oil goes I have always had my doubts about ATF. I work at a John Deere dealer, Our "Hygard" trans oil comes in 2 grades, regular and low viscosity. They are designed for powershift transmissions in tractors which use the same type of clutches as automatics. They have the additives in them that regular hydraulic oil doesn't to smooth out the shifts. I think I'll give that stuff a try. If I don't like it I can always change it again. I am new to this sight so I'll have to spend some time and read the other posts about auto transmissions and decide what to do about my shifting problem. It really isn't all that bad, just a little annoying. I usually just turn off the o/d until its warmed up or drive 55mph + and it works fine.

Thanks again for the help! Great site!!