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Discussion Starter #1
For some reason a few months ago the speedometer on my 94 Ram started reading anywhere from 20 to 40 mph slower than the actual speed. at actual 45mph the speedometer reads 25. At 65 mph the speedometer shows 35. What could possibly be wrong? Nothing is slipping and the tach reads the same as it always has.
 

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The gear is on a plastic shaft. I had something similar happen. The shaft was sheared but had enough friction to turn the sender. R&R is covered in the FSM.
 

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Dug into this a little. Looks like the Driven gear abd sender is OK. The Drive gear inside the transmission turns pretty freely. the splines in the plastic gear must be stripped. What all do I need to remove to get to this? Trans is a 2WD 5 speed manual.
 

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Drop the driveshaft and remove the tailhousing. You'll need a 12-point 10mm socket (Almost positive it's 10mm... might be 12mm) to remove the tailhousing. There's a sort of snap-ring holding the plastic gear onto the tail shaft. Tube of RTV to seal the tailhousing back on after you replace it.
 

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Oh! And all the gear oil will drain out too, so you'll need a few quarts to fill it back up. I use Redline MT85... You may need to support the transmission with a jack and remove the transmission mount too (Good excuse to replace that guy if it's 20-year old rubber), but you don't need to pull the crossmember.
 

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Discussion Starter #6
That doesn't sound like too bad of a job. Anything else I should look at while I am in there? Thanks!
 

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When refilling. Just be sure to use the proper lube in the NV4500. They take a special fluid. Use Redline MT85 as said above, or get NV4500 fluid from Dodge or GM. Dont use regular GL5 gear lube. It will eat up the syncros in the trans.
 

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Discussion Starter #8 (Edited)
Well I am at a loss. I put the truck up on my lift to do some more looking around since I could see better. I can't find anything wrong with either gear. Now where do I go? Is a gallon of MT-85 enough to refill?
 

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It is 8 pints, so something like 1.2 gallons. You have the tailhousing off, or you are looking through the hole? I think you said in a previous post that the plastic gear on the tailshaft was spinning fairly freely...
 

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When refilling. Just be sure to use the proper lube in the NV4500. They take a special fluid. Use Redline MT85 as said above, or get NV4500 fluid from Dodge or GM. Dont use regular GL5 gear lube. It will eat up the syncros in the trans.
The Castrol Syntorq LT fluid, which was the OE specified lube that GM and Dodge repackaged and sold, has been discontinued by Castrol. Redline MT-85 is the de-facto replacement. I've personally run the MT-85 and can confirm it works just as well (or even a bit better) than the factory fill.

BTW, before Redline made MT-85 specifically for the NV-4500, they specified a 50-50 mix of MTL and MT-90 for the application. This mixture is identical to what is now packaged as MT-85. The reason I mention this is in case you need fluid now, can't get MT-85, but you CAN get MTL and MT-90. The mix works exactly like MT-85. If you're in a hot climate, and especially if you tow in a hot climate, straight MT-90 is fine as well. I'd imagine f you're in an arctic climate, straight MTL would be better than MT-85. It's nice to have the options.
 

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Well I am at a loss. I put the truck up on my lift to do some more looking around since I could see better. I can't find anything wrong with either gear. Now where do I go? Is a gallon of MT-85 enough to refill?
The spec fill quantity is 4 quarts (a gallon). It has been found that adding between 1/2 quart (1 pint) and 2/3rds quart keeps the input bearing and gear lubed better and it runs cooler, especially when towing. I run 4.5 quarts myself and have had no issues with blowing oil out of the vent or other problems, so that is what I stick with.
 

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The spec fill quantity is 4 quarts (a gallon).
See below from the FSM. Spec == 8 pints == 4 qts == 1 gallon US. "Spec" though, is actually to the bottom of the fill plug... so it cannot be overfilled.

With that said I have never personally filled a 'stock' NV4500, I have a cooler on one of the PTO's that adds a bit of space and it's been around 5 quarts to get the job done.
 

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