AWD front driveshaft q's

[97 EB Mike]

As many folks here have experienced, I have a failing cv in the front driveshaft of my 5.0 AWD truck. I'm a NAPA employee and looked there for a new shaft, but didn't find one listed for the Explorer. However, I did find one for a 97 AWD Mounty thanks to searching the forum. Is there a difference in the front shaft between the 2 trucks? I've also read in a post on this forum that mid 97 the location of the engine was changed, changing the length of the front shaft. The NAPA shaft is listed as being 22 3/4". I'd be happy to crawl under my truck to make sure it is the right one, but I don't know exactly where that measurement should be taken. Do all 97 AWD front shafts have a 6 bolt flange, or was that changed at the same time of the length change? Any insight is greatly appreciated. Thanks in advance, and a very happy Thanksgiving to you and yours!

 

[OneLever]

What date is the manufacture of your vehicle? You can find it on the driver's door jamb sticker. Mine is 07/97 has a six bolt transfer case flange, and a 22 3/4" long front driveshaft. I'm not aware of which date a change might have occurred. You can buy a re-manufactured one an auto parts stores, a new OEM one from vendors on this site, or buy a new CV joint and boot and rebuild the joint yourself and keep the shaft. The length is measured on the shaft, not including the joints, from the center of one end's weld to the center of the weld on the opposite end of the shaft.

 

[97 EB Mike]

My build date is 6/97, and I too have the 6 bolt flange. I'll slide under it later today to check the length. I imagine for now I'm looking at a reman unit. I plan on swapping the t case, but that isn't going to happen until spring at the very earliest and I don't think the shaft I have is going to last that long. Thanks a ton for the info, and have a great day!

 

[OneLever]

Some helpful information, the specs for my bolts were as follows.

Front driveshaft to Transfer case:
Head = 8MM
Bolt = M8-1.25x49
Grade =10.9
Other markings = KXV
Quantity = 6

Front driveshaft to Front differential:
Head = 3/8" and T30
Bolt = 1/4"-28x9/16"
Grade = ?
Quantity = 4

I had to use a mini butane torch, pointed away from the fuel lines, and a deadblow hammer to loosen the U-joint bolts at the front differential. My 3/8" wrenches just rounded off the exterior of the head. So I tried a T30 torx bit before heating/banging and it just snapped. Good thing I had craftsman so I exchanged it ("Must have been defective...") and the second one worked.

The transfer case bolts gave me no problem. Although I did have to use about 9" worth of extensions to reach it over the cross member. All the bolts had yellow thread locker on them not red. So I think the swift hammer blow helped more than my butane torch. I have only just now gotten around to cleaning up the threads and am about to install a new driveshaft.

Also read the warning on drifting in park after removing the shaft: Link

 

[97 EB Mike]

Thanks for the specs...after my shift today I'll probably tackle it. Is there any logical reason not to put a little anti-seize on those fasteners for re-installation? Do I need new bolts due to stretching? Had planned on using the same fasteners (unless I ruin them taking them out) with a little antiseize to make it easier the next time. Are there torque specs that should be used? Didn't really think of that til just now... Thanks for your help!

 

[OneLever]

Thanks for the specs...after my shift today I'll probably tackle it.

Get at least two T30 bits, I recommend Craftsman so they'll replace the ones you break.

Is there any logical reason not to put a little anti-seize on those fasteners for re-installation?

Yes, that is part of the drive line which undergoes extreme amounts of movement and vibration. As a matter of fact I strongly recommend using blue Loctite when you install a new shaft. If you used anti-seize the fasteners will work their way loose and you'll probably have the driveshaft disconnect while driving. It doesn't take much I believe Loctite suggests only a drop on the end of the bolt.

Do I need new bolts due to stretching? Had planned on using the same fasteners (unless I ruin them taking them out)

Take a look at the threads of the bolts to see if they are damaged. If not you can probably reuse them. I haven't seen anything about them being one time use only. I did purchase a 40 piece Craftsman thread restorerer kit to clean the threads on the bolts and their holes. The old thread locker was causing them to snag a little and that throws off your torque readings.

I learned that it is better to use a tap and die set specifically labeled for re-threading. Regular tap and die sets will remove new metal instead of just cleaning the threads, and that will actually cause a looser fit than before. That Craftsman set is made in the USA unlike their regular tap and die sets so I was more comfortable with its quality. Given how difficult it was to remove the U-joint bolts I decided that it is almost necessary to reuse the old ones because I couldn't find any other bolts which had the internal Torx head. I replaced the old U-joint straps though because I suspected they may have warped slightly from driving around with a bad CV-joint in the rear for awhile. The internal Torx head grips much better than any other fastener type I have dealt with. It is not an Allen head! Allen bits will round out the Torx pattern.

If you do clean the threads with a re-threader you will want to use an oil. For this purpose 3 In One oil will work well and can be bought at any local hardware or auto store. After cleaning the flange threads on the vehicle you need to clean off the oil or it will affect torque readings as well. I suggest careful use of brake cleaner with something behind to catch over spray, and then drying with compressed air. Also, clean the bolts before the holes to make sure you're using the right diameter and pitch. It is far easier to replace a fastener than to tap new threads. Is all of this necessary? Probably not but when I do a job I try to do it right the first time.

Are there torque specs that should be used?

Yes, I don't have them with me at the moment but I'll post them when I get home.

 

[OneLever]

Note this information is given for 1997 AWD and 4x4 Front driveshafts. I do not know if it applies to other years.

The four Front driveshaft to Front differential bolts are torqued to (11-15 lb/ft). The six Front driveshaft to Transfer case bolts are torqued to (22 lb/ft). Although not stated in the manual I would do the final tightening in a star pattern to reduce warping, particularly on the Transfer case flange. Both of those values are lower than I expected, but they are the ones listed in my manual.

Also, because the driveshaft is a balanced unit the manual says to index it with respect to both flanges so it is installed in the same position. What is not stated is how you are supposed to orient a new driveshaft. My guess would be to install it by just torquing the bolts to spec without Loctite. Then drive around a short amount of time to see if any noise, vibration, or harshness develops. If so try rotating one or both flanges with respect to the shaft to reduce the NVH.

Once you get it minimized re-torque all the bolts to spec with Loctite.

 

[97 EB Mike]

Well, job is done. Went very smoothly. The tip I could add for anyone changing one in the future is to use both the T30 and a 3/8 open end wrench on the strap bolts on the front differential end. I was able to remove them without breaking the T30 this way. There were also 3 bars with a pair of holes each behind the bolt heads on the transfer case side. I can only assume they were there as a torque evening device. They didn't seem to serve any other purpose, and I didn't see any markings to make me believe they were balance weights. Start to finish, about 2 1/2 hours with a few cigarette/bathroom/warm-up-because-my-garage-doesn't-have-heat-yet breaks.

 

[OneLever]

Good to hear!

The tip I could add for anyone changing one in the future is to use both the T30 and a 3/8 open end wrench on the strap bolts on the front differential end.

That's a clever idea. Given how low the torque specs are for the U-joint bolts it must be dirt and rust that makes them seize in place.

There were also 3 bars with a pair of holes each behind the bolt heads on the transfer case side.

Mine had those as well. Because they appear by feel to have the same weight and are evenly spaced around the shaft I don't think they are balancing weights. I suspect you are right in thinking they are just specialty washers.

Did you have to change the orientation of the flanges with respect to the new driveshaft to reduce vibrations. Or was it good from the start?

 

[97 EB Mike]

Did you have to change the orientation of the flanges with respect to the new driveshaft to reduce vibrations. Or was it good from the start?

The jury is still out on that one...The vast majority of my vibe issues are solved. I honestly believe that what is left in the way of vibration could likely be solved with an alignment and tire rotation. That's what it feels like. Time will tell...

 

[OneLever]

I finished installing my own front driveshaft two days ago. After doing so I would like to amend some of the suggestions I made based off experience.

1. I would not clean the threads in the bolt holes. After cleaning two U-joint bolts and two U-joint holes with the re-threading kit I checked the cleaned bolts for play in both cleaned and uncleaned holes. I found that there was a noticeable increase in play in the cleaned holes. Not so much as to prevent it from fastening, but enough to know that the re-threading tap had taken out new metal.

2. I would clean the bolts themselves though. This did help make their installation a smoother motion without introducing noticeable play.

3. I kept the orientation of the transfer case flange with respect to the front differential flange the same as they had been previously. Because of the paint marks I left on them before disconnecting the old driveshaft this was easy. I have not noticed the sounds of a terribly imbalanced new driveshaft. I did notice a high frequency whirring sound when climbing up hills (load applied), and I believe this is the front differential which likely needs a fluid change.

4. While using Loctite would be good if you have the chance I did not. The clearance between the bolts and ground with my truck jacked up was just barely enough to fit a torque wrench on them with u-joint adapters on my wrench extensions. It took me over two hours to torque all the bolts down to spec. Mainly because its so cold outside that after two bolts my hands would go numb and I'd have to go warm up. But even under warm weather unless you have a lift you might not be able to finish torquing them before the Loctite sets. So use your own judgement.

I have contemplated removing only one bolt at a time and applying Loctite to it. Then installing it and torquing to spec before the Loctite sets. That might give me enough time to finish one bolt at a time before my hands go numb. However, I am not certain what sort of warping this would induce on the transfer case flange.

Does anybody with a mechanical engineering background have an opinion on this?

 

[97 EB Mike]

No engineering background, but here is my experience:
I didn't clean the u joint holes, and I used new bolts and straps because I simply don't like the design of the old bolt heads. I didn't see any noticeable play.

It was impossible for me to keep the orientation exactly the same as it was before removing the old shaft. The yolk on the new shaft must have been welded in an "in between" position compared to the old shaft and the t case flange bolt circle. I had to spin the front wheels to be able to align the two yolks and install that end of the shaft. That being said, I do have a vibration, but I attribute it to being long overdue for an alignment, and, in all likelihood, unevenly worn tires. I know this is a HUGE no no on an AWD, but at this point it is what it is. I intend to be the last owner of this truck, so whatever problems I cause, I'll be the one to deal with. It isn't going to blow anything up overnight, and when something does cut loose, it'll give me a good excuse to continue my build.

As for loctite and torque specs...wellllll...they didn't seem all that important in the middle of the night in a cold garage. I used the "that feels tight enough" approach. If something gets loose, I'll address it at that point. Maybe I'll need a new u joint, maybe I'll need a new shaft. Maybe I'll scrap the whole system and get my 4406. But I've never used loctite when installing any other driveline components, and I've done a few. I can't imagine that, with such a low torque spec, you'd warp the t case flange if you decide to remove the bolts individually and loctite them. But, I can't imagine that if you leave them where they are, with no abnormal vibration, you'll have any problem with them coming out. That's just my opinion. That and a $5 bill should buy you a cup of coffee at even the top end fancy coffee shops.

 

[OneLever]

I didn't clean the u joint holes, and I used new bolts and straps because I simply don't like the design of the old bolt heads. I didn't see any noticeable play.

This is effectively the same as what I did. I used new U-joint straps and cleaned my old bolts to make them like new. But did not clean (most of) the holes.

It was impossible for me to keep the orientation exactly the same as it was before removing the old shaft...

To be honest, now that I think about it the balance of the driveshaft by itself is probably the most important issue. Perhaps the shop manual states to do that for ease of installation when they put the new one on.

I do have a vibration, but I attribute it to being long overdue for an alignment, and, in all likelihood, unevenly worn tires.

Does it occur while under heavy load or all the time?

As for loctite and torque specs...wellllll... I used the "that feels tight enough" approach...If something gets loose, I'll address it at that point.

That's pretty much how I felt but I went ahead and torqued to spec. Also checked the bolts several times over the past few days with no problems.

...I've never used loctite when installing any other driveline components

Yeah, the manual did not call for it. I only suggested it because it was on there when I took them off.

I can't imagine that, with such a low torque spec, you'd warp the t case flange if you decide to remove the bolts individually and loctite them.

Very good point. After some hindsight on the question I realized that even if the transfer case flange was warped. As long as the bolts are secure the CV-joint would probably make up for it because of the way it moves.

That and a $5 bill should buy you a cup of coffee at even the top end fancy coffee shops.

Well thank you. This has been an enjoyable and insightful discussion.

 

[97 EB Mike]

To be honest, now that I think about it the balance of the driveshaft by itself is probably the most important issue.

That's the same thought I had. I even called my dad (an industrial mechanic with about 40 years experience) to make sure I wasn't crazy. He agreed, so I wasn't too concerned about having to rotate the front axle.

My vibration doesn't seem to have anything to do with load, but more overall speed and direction. It shows up at around 48-50mph, and clears up at a little over 55 if I'm going straight. Seems to be there at lower speeds if I'm in a relatively sharp corner. Knowing what I know now, I wish I would have taken the truck for a short drive without the front shaft. I can still turn figure 8s at full lock idling on pavement, but I can't help but wonder if the VC in my t case is bad. There are a ton of factors that I suppose could be causing it. But at this point, the alignment is at the top of the list of things to do. Mostly because it needs done, even if it isn't the culprit. I should, however, clarify: 95% of my vibration issue is cured. I no longer lose the carbonation from a bottle of Coke resting in my cupholder. And with my maintenance mentality, a little vibration is to be expected. After all, this sucker's closing in on 15 years of service, and the guy that had it before me certainly didn't help matters any.

Just out of curiosity, whose shaft did you use? I put in a reman from NAPA (A-1 Cardone), and I think it was that particular reman that I read about having balancing issues on other threads here. Doesn't seem to be the case with mine, or yours if that happens to be what you used...

At any rate, I'm glad we both have trucks that pull from the front again. On to the next project...

 

[OneLever]

I can still turn figure 8s at full lock idling on pavement, but I can't help but wonder if the VC in my t case is bad.

As long as there's no odd noises or hopping when you do this I think you're transfer case is fine. I left my driveshaft out for over a year and people claimed mine would fry. It did not and is working great.

at this point, the alignment is at the top of the list of things to do... 95% of my vibration issue is cured.

Yeah, I'd say you're doing fine then.

Just out of curiosity, whose shaft did you use? I put in a reman from NAPA (A-1 Cardone)...

I used a "Fenco DS9450; Length 23; Type A18" from Advance Auto Parts with 20% off online for $160 total. Actual length was 22 3/4" like I said above. Interestingly enough I have the invoice right here and AAP's website does not list it anymore. Instead they list this wrong part which has the part number DS9451 and is an inch too long.


Edit: Here is a picture I took of the box mine came in:

Link to larger view.