I have researched this till I'm blue in the face and would like some answers of my own. I have a friend with 93 d350 5 speed getrag tranny and 3:55 rearend. 2wd. Cummins diesel. WE have had trouble with the right angle ratio adaptor on the VSS arrangemnt. This truck ruins one about once year.
THe dodge house here has been no help and says they are hard to get even when i give them the VIN# and if they get one it will be 120.00. I took the old one apart and it seems that the bushings are wearing out and the gears are not properly making contact. I have read that the Right angle ratio adaptor is just for fine tuning the speed of the driven gears to the vss. I was wondering If I remove it and screw the VSS direct onto the driven output , will it greatly effect the Speedomter reading like 10-20 mph or just a little like 5mph. I can live with a little as we are running taller tires than what came on it and some speedometer is better than none. I asked the dealer about replacement bushings and they were at a loss. I welcome any information some of the first gen owners may have about this.

Thanks zspear1

 

the right angle gear reducer changes the speed, and without it, the speedo wont read at all, at least thats been my personal experience.
I bought a used truck once that was missing it, and I couldnt get any readings on teh speedo until I replaced it.
The Odometer and Cruise wouldnt work either.
I havent heard that they are rebuildable at all, they are not a servicable unit.
When you say it is ruining one , whats it doing? they should last indefinitly....

 

This one has a metal housing and the bushing that holds the pinion gear in place is worn so it lets the gear slide back and forth and not engage the ring gear. THe one I have has fittings that a 15/16 wrench can take loose. It even has grease zerk on it for service periodically. I have not had experiece with this truck in the past till this last year but my friend who owns it says he has gotten them changed alot and more frequent when it was used all the time (he's owned it since new). The shop he used is out of business as the owner past away I guess he was real keen on what ratio adaptor that truck has to have. I have no earthly idea I wish it was like a ford or Chev where the drive and driven gears in the tail shaft housing determined the speed of the VSS, but that is obviously not the case. And those gears are in good shape and so are the square shafts.

 

On ours, the Pinion drive gear in the tailshaft determines the speedo/gear ratio/tire size ratio.
The pinion drive gear spins the VSS, which drives the gear reducer, which sends teh signal to teh PCM and hence to teh speedo...
IF he is wanting to change ratios, then he will need his tire size adn rear end ratio to take to teh Dodge dealer, who can look up the correct one.

It sound from what you are describing that the VSS may also need replaced.

 

That makes sense, I thought the VSS was OK but that goes without saying , I hooked a drill up to it to verify operation but with the Drill I have no idea how fast it is going to correlate what the speedometer says, which was fifty mph when I did it. I know the Vss is cheap I will go and get one of those and try the dodge house again with rearend ratio, tires zize vin# ect ect. see what they can do. THanks.

 

Does he grease the adapter? One pump every oil change usually keeps them happy for quite a while.

 

I think he does and to often becuase there was grease inside and outside that thing like someone had pumped alot through it, but it is definatley loose and worn after I took it apart. Is there any special high speed grease you should use ?

 

I just use the same chassis grease as on the rest of the fittings. One pump only, though - you can split the thing open if you keep pumping.