Speedo going out???

[Nic.Durrant]

I have been getting some weird readings on my speedometer. Like i will be going like 60 miles an hour and it will twitch and go up to 63 or 65 and addamitly go right back down to 60 miles an hour, and sometimes my speedometer will not work untill i let of the throttle. So im thinking its the speedo going out but im not sure. Also I was wondering where the speedo is on these 1st gens.



Thanks, Nick

 

[DanoT]

It might be the speedo sensor coming loose.

 

[RedRamAndy]

Hey Nick,

Not sure exactly how your 90 is set up. On my '89 D250 5 speed Getrag, the speedo is cable driven. Do you have a cable going to the head of the tailshaft on your auto transmission? If so, yours is cable driven too. If so, the speedo has a spinning magnet in it hooked to the cable that imparts a magnetic 'pull' on a sprung aluminum bell connected to the needle. A bushing could be worn allowing the magnet to rub on the bell making the needle jump. Usually though, that pegs the needle and ends up in some wild needle bouncing. If the twitching is slight, it might just be a dry cable. You can pull the core cable out from one end and oil it. ( I forget which end! Try the transmission end first, being the easiest to get to. )

If you have an electronic speedo (no cable at all, just wires), check the speed sensor. (the part it's connected to at the trans. ) I had a '90 Chrysler and this was the failing part when my speedo would go nuts. I had to replace it about every 80 grand.

I'm just not positive which style speedo a 1990 has.

 

[Bob Beauchaine]

'93s have a VSS that sends pulses to the speedometer via the attached wireing harness. I would check the VSS on the trans to insure there no broken wires and that all is tight at the trans. I can probably get you the specs on the pulses if you want them. Let us know what you find.



Bob

 

[RSchwarzli]

I get this about once or twice a month, and it been doing it for 7 or 8 years. Only lasts for a few seconds. Also a 1990.



We have an electric sender on the side of the T case. You will see a 3 inch long piece with a wire on it. That is the sender. Half is gear driven, the top half is the electric part.



From what I have been told, it is the sender. This makes sense as this was common on Dodge vehicles of the era.

 

[Nic.Durrant]

Yeah my truck doesnt have a t case.

 

[RSchwarzli]

Riiiiiight. Duh! Sigs are there for a reason! I should learn to read them!

 

[JBroyles]

mine too but registering twice as much

I have the 5 speed manual and my speedo and odometer are reading twice the actual mileage... i replaced the replaced sensor but didn't fix problem... who knows? you find anything out, let me know and i'll do the same!

 

[Bob Beauchaine]

JBroyles



What manual transmission are you running?



If you fill in your sig. so we know what your running we can give you better advice.



Bob

 

[JBroyles]

I'm not sure what transmission

I have the 1993 dodge d350, dually diesel with the 5. 9L engine, 5 spd manual transmission.

What's the easiest way to get the transmission info?

Thanks

 

[JBroyles]

My Dad says it's a Getrag transmission

 

[Bob Beauchaine]

The problem you describe is consistant with the swap to a NV4500HD. Just to be sure crawl under your truck on the passangers side about 2" in back of the fill plug on the trans. there is a plate. That plate should show that it is a G360 - Gertag 360 - if indeed it is. Let me know what you find.



Bob

 

[JBroyles]

You're correct and

Ya it's a Getrag 350 says on the plate along with this number...

52108006

Thanks!

 

[bopplumb]

My 93 4X4 had speedo issues and I found out when the previous owner did a trans swap they forgot to install the reduction unit between the sensor and the pick-up in the transfer case, "it was gone". It took allot of research but I found what was missing and located a New old stock part out of Mich. and it fixed the problem.

 

[Bob Beauchaine]

It sounds to me that there is the wrong drive gear running the VSS. There are two ways to solve this particular problem. First way would be to install the correct drive gear. For that you would need to go to Dodge for the correct number and then install a new drive gear. This depends on the dealership you choose and their willingnes to help.



For the second fix you will need to follow someone at a set speed - say 40 mph. They run at 40 and you run a safe distance behind them. Try to keep a set distance to get an accurate mph on your speedo. With that info you can tell a good speedo shop what the numbers are and they can build you an adapter that will attach to your VSS at the trans. This will then correct the pulse count and correct your speedo.



Last but not least - or should I say the first step I would take is to set the correct torque on the trans output shaft jamb nut. The drive gear that runs the speedo is held in place by spacers, one on either side of the drive gear You will need to drop the drive shaft at the trans. You will see a nut holding the yoke on to the trans. This is the only thing that keeps the spacer/drive gear from moving. The torque setting on this nut is 290lbft. I have seen cases where as little as 1/8 to 1/4 of an inch can solve an erratic speedo. Notice I said - erratic - speedo bounce and non functioning cruise control are symptoms of this problem. Still I would do this first as it is the easist and least costly of the options I have listed.



If you have any questions PM meand I will give you my cell phone #. It might be easier to talk this out one on one.



Bob

 

[bopplumb]

I did the first, I went to Dodge and got the specs. Found what I needed and went searching. Fixed the problem.

 

[JBroyles]

Wow Bob's, Thanks a lot for all the information... between the 2 of you i won't need a dealership LOL. First things first, i'm almost positive my transmission is original, not only that but my cruise control isn't working either so there's a good chance it's the torque on the output shaft. But i still question it because my speedo is registering consistent smooth twice as much (not erratic) which tells me it could be the reduction unit or gear drive. This is difficult! Thank you Bob and thank you Bob for all the info, i'll try torquing down the nut and see how that works... if it doesn't fix the prob, we'll swap phone number and we'll talk!

 

[WyattEarp]

I switched my Vss a few years back and fixed the speedo needle which had died, wouldn't even register. My issue is my odometer mileage numbers it doesn't roll up the miles and hasn't for gosh knows how long, was like that when i got it, it worked for a bit after the new Vss but then stopped again, any ideas. My cruise works flawless no issues there. I figured and this is a rough guess my truck has around 300,000 on it. its showing 77600+ so it hasn't worked in awhile LOL. .

 

[Bob Beauchaine]

Wyatt



I have seen posts on this problem and from what I can gather 2 things come out. 1 Most recommend insuring that the grounds on the instrument panel are good as a first step. Pull the dash bezel and the the instrument cluster and check the printed circuit board for problems. If this does not help you might have to send the speedo out for a repair. I have wondered why you could not find a new working speedo in a junk yard. It should be cheaper and worth a try. My maintenance manual states that the speedo can be pulled out of the front of the instrument cluster. It also states that the speedo has to be pulled straight out and not twisted in either direction.



Hopes this helps.



Bob