No overdrive

[RobertGray]

On my 92 D250 I have no overdrive.
I have checked the gearbox oil level. changed the speed sensor and given the TPS a clean, the TPS is about 12 years old but looked clean anyway. The truck still won't change up into fourth, can anyone help?
I am a bit suspicious of the kickdown mechanism but I don't really know how they are supposed to work. I am more inclined to think it is an electrical fault, The connectors on the fuel pump (two blue wires) seem loose, are they related?
I know these gearboxes are basically a 727 with an overdrive, I don't know the actual model number of the box.

 

[Ozymandias]

OD is electric shift only, no mechanical.

 

[RobertGray]

OD is electric shift only, no mechanical.

So the kickdown mechanism only changes from 3rd to 2nd or 2nd to first? And the downshift from 4 to 3 is controlled by the throttle position sensor?

 

[Ozymandias]

From what i know yes, but I'm not that competent for the old stuff.
But for sure if the TPS is broken it wont shift into OD.
Do you have the factory service manual?

Read this > https://www.turbodieselregister.com/threads/518-automatic-adjustment-question.269437/

 

[BigPapa]

I would check your brake light switch, TPS, and transmission temp sensor.

I believe the ‘92 transmission was the A518. Basically a 47RH without lockup.

 

[cerberusiam]

The transmission is a 518 or 46RH in more current lingo. The kickdown linkage has no effect on OD, OD is a controlled by the SBEC based on inputs from the speed sensor and TPS. ANY glitch in the inputs will result in no OD. The OD shift also requires the OD mechanicals and solenoid all work, problems there will absent OD.

On the transmission case, driver side just above and in front of the rear cooler line you will find a 2 wire harness, that is the OD control harness. The larger wire of the 2 will have 12 volts on it with the key on and the auto shutdown relay working. Check for 12 volts before digging nay deeper

Easiest way to check if the problem is mechanical or electrical, mystery switch on the OD sense wire. The other smaller wire in the harness above is the OD sense wire, to enable OD all the controller does is ground that wire. If you scotch lock a wire to the smaller wire of the harness, run it to one side of a simple SPST switch, the other side of the switch to a known good ground (not the battery post, you want a chassis ground), when you flip the switch an complete the circuit OD should engage IF the solenoid is good and the OD unit is good.

If you have 12 volts on the supply wire and OD does NOT engage by grounding the sense wire either the solenoid is bad or the OD unit is bad, at that point you will have to dig into the trans to validate. Try that and report results.

 

[RobertGray]

Cerberusiam, Many thanks for that very clear reply, I have replaced the VSS already (I always keep one in stock) and have ordered the TPS delete kit from Geno's Garage. The first TPS lasted 16 years the second has been in 12 years. If that does not work I will follow your recommendations or at least get a mechanic to follow your recommendations.. The Dodge Engine Diagnosis Service Manual has also been helpful.
I live in Ireland where I have some trouble getting a good mechanic who is willing to do the work, I may have to learn auto electrics myself.
I will post again once I have the TPS delete kit installed

 

[BigPapa]

Doesn't the transmission temp enter in to OD function? When I had the '92 it wouldn't go into OD until I'd driven 2-3 miles in the winter when it was cold out.

 

[cerberusiam]

Yes, trans temp will keep it out of OD it it is too cold or too warm. That is part of the electrical parameters that needs checked once it is verified OD mechanically works. If you do not verify OD is mechanically functional it is just chasing ghosts because it is impossible to electrically actuate a broken mechanical system. The 518 OD's were problematic anyway unless they were tweaked and rebuilt. On a 28 year old truck that would be FIRST thing I would check.

 

[RobertGray]

Yes, trans temp will keep it out of OD it it is too cold or too warm. That is part of the electrical parameters that needs checked once it is verified OD mechanically works. If you do not verify OD is mechanically functional it is just chasing ghosts because it is impossible to electrically actuate a broken mechanical system. The 518 OD's were problematic anyway unless they were tweaked and rebuilt. On a 28 year old truck that would be FIRST thing I would check.

Many thanks,

 

[RobertGray]

Yes, trans temp will keep it out of OD it it is too cold or too warm. That is part of the electrical parameters that needs checked once it is verified OD mechanically works. If you do not verify OD is mechanically functional it is just chasing ghosts because it is impossible to electrically actuate a broken mechanical system. The 518 OD's were problematic anyway unless they were tweaked and rebuilt. On a 28 year old truck that would be FIRST thing I would check.

Hi
I got a mechanic to check the solenoid, and there is no sign of it working. So can you just replace the solenoid and is it a big job? Also where can I get the part? Also I need to replace the plug for the solenoid, can you buy a new one? I am looking into having the box rebuilt in any case though that might be tricky here in Ireland. I would be interested to know what you mean by tweaked.
Many thanks
Rob

Is this right?
https://www.transmissioncenter.com/...-pigtail-connector-for-overdrive-non-lock-up/

 

[cerberusiam]

Here is what you need to replace: https://cobratransmission.com/solen...tm_term=4585307089132151&utm_content=Shopping
The plug should be a 2 wire and if it looks close they probably used the same plug in multiple positions.

The 518 was short on clutches in all packs, had aluminum planetaries, OD was setup incorrectly for long time usage, and the pressure like anything OE unit were on the low side. There a re a lot of tweaks and changes to make the unit much more capable.

 

[Ozymandias]

Shouldn't be a problem to have that box rebuilt in Ireland. It's standard Chrysler and was widely used in all their cars sold allover Europe for the last 60th years.

https://www.google.com/search?q=aut...+Ireland&ie=utf-8&oe=utf-8&client=firefox-b-m

 

[RobertGray]

Here is what you need to replace: https://cobratransmission.com/solenoid-a518-46rh-46re-204045-1?msclkid=7d8216061f08145aee6f490a6ba79f13&utm_source=bing&utm_medium=cpc&utm_campaign=A. (DESKTOP ONLY) Shopping (January 18, 2019)&utm_term=4585307089132151&utm_content=Shopping
The plug should be a 2 wire and if it looks close they probably used the same plug in multiple positions.

The 518 was short on clutches in all packs, had aluminum planetaries, OD was setup incorrectly for long time usage, and the pressure like anything OE unit were on the low side. There a re a lot of tweaks and changes to make the unit much more capable.

Hi
The part was delivered yesterday, is it a simple job to put it in? Will an ordinary mechanic do or is it a job for an autobox specialist? If you can give me some simple instructions it will help me persuade the mechanic to do it. I would like to get the truck running with all four gears working, otherwise I will have to have it taken by a recovery truck to an autobox specialist and that will be in excess of €200. Then later in the year I will bite the bullet and take it for a transmission overhaul.
Many thanks again.

 

[cerberusiam]

Pretty simple to do if the mechanic has any chops.

 

[Ozymandias]

If you want to do it yourself, check YouTube for the how to.

 

[RobertGray]

Pretty simple to do if the mechanic has any chops.

Obviously most American mechanics could do it. I have owned this truck for 20 years during which I have lived in England, Spain and Ireland. In England there is a healthy American car interest and I lived within five miles of a very good American car specialist and there are plenty of spares and other specialists. In Spain I was very lucky and lived near to the only mechanic who actually owned an American car (73 Lincoln MK IV) within about 300 miles, he is still a friend, the Cummins agent was not far away either. Here in Ireland I am on my third mechanic in five years and having trouble getting what seems like simple jobs done. The nearest automatic gearbox specialist is 100 miles away.

 

[Timd32]

Good American mechanics are just as rare in my parts of NJ.

While we have a good dealer network for new cars and trucks, the older stuff like my 96, good luck sending that to a local place around my parts. It would be a week or two to get an appt. and hope they don't break anything else while they are in there.

Good luck on your repair. It is pretty straight forward if you can find a place.

 

[RobertGray]

Good American mechanics are just as rare in my parts of NJ.

While we have a good dealer network for new cars and trucks, the older stuff like my 96, good luck sending that to a local place around my parts. It would be a week or two to get an appt. and hope they don't break anything else while they are in there.

Good luck on your repair. It is pretty straight forward if you can find a place.

I was thinking about it last night, I have the service and engine diagnosis manuals on a flash drive and a copy of Chiltons maintenance manual which I always take with the truck to the garage, the current lot are Polish and I suspect struggle with reading English. The Irish mechanics don't even seem to want to look at them. I will read the manual myself and report back when I have got the part fitted.

If you want to do it yourself, check YouTube for the how to.

I see what you mean, it looks very simple. I would attempt it myself except I am in the process of building myself a carpentry workshop/garage and am not going to try when I have to crawl under the truck and do it outside .

Many thanks to all

 

[RobertGray]

Hi guys I need some emergency help. The truck is on the lift at the mechanic's garage.
We changed the solenoid and 3-4 accumulator spring put everything back and four quarts (3.75 litres) of fluid now the truck will shift from park to reverse and work in reverse but we cannot shift into drive.
He disconnected the shaft outside the gear box and we can't manually move the manual valve shaft fully out. I think it is in for park.
Two things I noticed when the mechanic was doing the work one the solenoid wires were routed over the valve body and not under it as in all the diagrams. We cut the old wire and ran the new wire as per the diagrams. The second thing was that there appeared to be only one spring when we removed the 3-4 accumulator housing. All the diagrams showed two. There was no sign of the smaller spring the clutch valve spring and plug that is detained by the boss on the accumulator housing. I was not watching the mechanic when he removed the housing but he said he was sure there was nothing there and we searched the whole place as springs can go flying.
I am wondering if the rooster comb was misaligned when he removed the accumulator housing, but it looks as though you have to remove something else to get to it.
Any ideas?