Front propeller drive shaft

I’ve been in search of the front drive shaft on a manual 5vzfe 98 4R and I had a salvage yard tell me the gear ratio matters for the drive shaft - so how is that the case ? Can someone explain this to me

 

It does not matter for the actual drive shaft. It matters that your front differential and rear differential are geared the same to drive 4wd. Not sure if the junk yard attendant was just confused, but the shaft doesn’t care…

 

Ok - are diffs the same as far as front and back ratio the same as I have not altered either of those ? And does it matter whatever the final number is ? For example a manual trans doesn’t require a specific ratio as long as the front and back match - is that correct ?

 

Yes. As long as you didn’t do anything to them they already match (you would know immediately in 4WD if they didn’t). The manual does not require a specific gear ratio, if you originally had an automatic with an e-locker it’s probably 4.30, I think OEM manual was usually 4.10 IIRC. There are some that are 3.73 and some at 4.56, but those are more rare, and doesn’t appear to have a rhyme or reason to it that I know of. However, it doesn’t matter, a popular mod is to regear both the front and rear to 4.88 for those running heavy skids/bumpers or larger tires. Just moves the truck along better.

You can figure out your gear ratio by jacking a wheel up and counting revolutions if you want

 

Maybe you can explain something to me as well and I don’t mean to take all your time. They talk about automatic disconnecting front differential and locking rear differential to my knowledge. Neither one is that, but I don’t even know how to tell on that, I mean, I have a shifter originally where you could Change between two and four wheel so that would maybe make me think that that’s the case but the differential on the front had some kind of vacuum connections to it so I’m not sure what that is

 

The only thing from factory yours would have is a rear E-Locker, which would be an open differential unless you “lock” the diff in 4LO. You can check by seeing if there is a button on the dash to left of the Steering wheel. Alternatively, if you post a pick of the rear differential we can tell you, it has a mechanism attached to it. If you don’t have either, then you have an open rear differential. The front diff on these trucks come open, any lockers on the front would be aftermarket.

the Vacuum line you say you have on the front differential is curious, can you post a pic? I suppose the PO could’ve added an ARB air locker, but again you should have buttons on the dash (and a compressor) if that were the case.

 

The shifter from 2WD to 4WD controls the transfer case which activates the front driveshaft and differential to put you in 4WD. Standard 2WD & 4WD has both rear and front diffs “open” in that the wheels can turn at different speeds (helps with turning etc). A locker is different entirely in that in lives within the diff and locks the gears, forcing both wheels to spin at the same speed. This is helpful for when you have severe traction issues, like one wheel in the air, as an open differential would send all the power to the path of least resistance (the wheel in the air), whereas locked, your wheel with traction could move you out of the obstacle.

 

I will do that. Appreciate all the help ! This is a great community !

 

Here is some pictures of front diff

 

Sorry here is one

 

Ohhhhhhh ok yeah, that’s the auto disconnect and breather. This just automatically disconnects the hubs and axels from the driveshaft. The ADD is so you can do 4wheel on the fly rather than manual hubs that you need to stop and lock manually. I get your question now. Most (all?) 3rd gen’s have that

 

2001-02 use electric actuated ADD

2000 and below use vacuum actuated ADD

All 3rd Gen 4R are ADD from the factory

 

Ok I should have figured that out!