Quick help: Rear axle u-bolt torque spec.. - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 07-23-2005
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Quick help: Rear axle u-bolt torque spec..

Hey all,

I'm installing my James Duff Traction Bars today (photos to follow). I have them all moded up (I hope) to fit my LII's 31-spline axle.. The one thing I've realized I don't have is the spec for what to torque the ubolt nuts back down to once I reassemble w/ the plate installed.. Can anyone answer this quickly?! I'm going to do some searching.. already been through TRS and ORR, but I thought I'd ask now in case someone lurking knows off the top of their head.

Thanks,
-Colin
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Old 07-23-2005
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um....hmm i use the impack...the good one we have...ya it aint coming off...
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  #3  
Old 07-23-2005
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120 ft\lbs directly from the SuperLift Instructions
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Old 07-23-2005
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Excelent, thank you.. Off to install!
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Old 07-23-2005
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no pics yet??????????
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Old 07-23-2005
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Quote:
Originally Posted by 2003Ranger
120 ft\lbs directly from the SuperLift Instructions
The Ford factory shop manual says that the U-bolt nuts are to be torqued to 76 lb-ft.
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Old 07-23-2005
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Will overtightening hurt anything.. within reason..
I'm not talking about tightening them with the "earthquake" 675lb-ft impact wrench here....

Rand
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Old 07-23-2005
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Quote:
Originally Posted by Rand
Will overtightening hurt anything.. within reason..
I'm not talking about tightening them with the "earthquake" 675lb-ft impact wrench here....

Rand
I would stay close to the factory-recommended torque spec. The 120 lb-ft quoted is over 50% higher than the correct 76 lb-ft figure. That's way too much IMO.
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Old 07-23-2005
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I think im going to retorque mine ;p
I had them off to put my duffs on.. didnt have a torque wrench handy..
So I just did them hand tight then as tight as i could easily get them
with a ratchet.. then a bit more with a breaker bar... I doubt it was over 100ft-lb though.
Since I'm putting on the new rear shocks tues... should be an ideal time for that.

Rand
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Old 07-24-2005
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The higher torque specs are provided from Superlift since they probably include replacement U-bolts that are a larger diameter....
What can happen IF you overtorque the U-bolts 50% or more.... ????SSSTTTTRRRRETTTTCCCCHHHHHH or more likely SNAP goes the bolt !!!!!
After you have driven the truck for a couple days.... you have to retorque the U-bolts since they were stretched when tightened... and loosen up when settling in.....

OR 4x4
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Old 07-24-2005
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Quote:
Originally Posted by OffRoad 4x4
The higher torque specs are provided from Superlift since they probably include replacement U-bolts that are a larger diameter....
Exactly what I was thinking.
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Old 07-25-2005
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Welp.. Unfortunately I didn't check the forum until this morning. I blindly followed the 120 ftlbs suggestion. There was no snapage (fortunately) but it did require a good deal of effort to torque them that much. I will once again pull the rear wheels and retorque to ~76 ft-lbs (what a weird number BTW!) ASAP. Thanks Bob..

One thing I noticed was that my LII had 22mm (or was it 21mm?!) nuts on the u-bolt. I had read somewhere that all I would need was a 19mm socket, which is as large as a socket as I had. (Maybe the LII has larger nuts , can anyone confirm that non-LII's have 19mm nuts on the u-bolts?!) This came as a shock to me as I discovered this when I already had the driver's side wheel off and was ready to install the bracket. I was anxious to install the driver's side bracket as quickly as possible so that I could paint the passenger side bracket. Both brackets required some rather agressive modification to fit my LII. Fortunately I found a 7/8" boxed end wrench that our machinist uses for operating the chuck on one of the end mills. He locks up most of his tools overnight and for the weekend, but that was within reach. After fitting the driver's side I re-assembled everything and drove to Sears to get a new socket set w/ the larger sizes.

At any rate, I got the things installed. As Bob has noted in the past, JD seems to be onto yet ANOTHER design for the front bracket.


As you can probably see in the photo, I had to bevel the bottom inside edges of the bracket to make it fit my spring plate. I also had to slot the holes for my wider/larger u-bolts. This took me most of the day as all I had was a set of files.

The finish is quite poor, as has also been mentioned. I chose to repaint mine. All I had handy was some flat black spray. I think that will do fine. It isn't as pretty as other's have done w/ that neat sky-blue gloss, but it's done. .. And paid for. I had to repaint the brackets several times as I found out that my original modifications would not fit as perfectly as I had hoped.

Installation took my slow-*** most of the day, including modding and painting the parts. However most of that was modding the parts for my LII. Once the parts were modified and painted, it took me about 2 hours to install everything. Of course that was w/ me doing nearly everthing twice, as I nearly always seem to end up doing. I originally mounted the passenger side bar to the rear-most hole in the bracket. When installing the driver's side I found I could use the front hole.. and decided to re-do the passenger side the same way.

My initial impressions of the things are that they are pretty good. I'm not as impressed w/ them as other's seem to be. This isn't my A-#1 all-time favorite mod.. at least not yet. It has taken away some of what I used to call 'slop' in the driveline. I always figured it might be backlash in the trans and/or diff.. but it seems obvious now that some, if not all of that is what people call 'axle wrap'. I've been making an organized effort to drive slowly and shift very early (< 2000 RPM) in the hopes of saving some gas. Previously I had to be very smooth w/ the clutch not to have some lurch when shifting at those RPMs. Now things seem to be a little more forgiving.

I did a hard launch from some soft dirt and onto pavement after 10 or so yards. The truck seemed a little more planted in the dirt (both tires easily threw dirt) and both tires definitely chirped when I hit the blacktop. I'd call that an improvement.

The rest of the vehicle's handling, at least on street and on dirt roads (what I've been able to test so far) seems entirely unneffected. I did a panic stop on a back road and these bars don't seem to change much there. The tires might have heald a bit better w/o as much chirp.. but I can't say for certian. I did manage to panic stop so hard that the fuel cuttoff was activated. That's the first time that has ever happened to me. I had to push the truck off the road and dig out the user manual to figure out where the reset switch was. Fortunately she started right up after that.

Photos of the install are here:
http://www.pbase.com/nhbubba/jdtractionbarinstall

I might be able to do a play-by-play how-to if there is interest. TRS has something, but it isn't all that well illustrated. It might be nice to have one central how-to w/ all the gotchas and info (like that torque spec) listed. I figure my LII is probably going to be pretty much the WORST case cenario for this install.
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Old 07-25-2005
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Good job, Colin!

I feel that the JD's improve the rear suspension in a couple of ways:

Wheel hop: I used to get this on the street launching moderately hard. With the JD's, it is much more controlled. A bit of off-road hop is still there but it's worlds better than the factory set-up.

Slip-yoke bump: One of my all-time Ranger/F-series pet peeves, especially with manual trans 4x4's. The JD's make it disappear and, to me, that improvement alone would make them worth the price of admission.
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  #14  
Old 07-25-2005
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Quote:
Originally Posted by rwenzing
Good job, Colin!
Thanks!
Quote:
Originally Posted by rwenzing
Slip-yoke bump: One of my all-time Ranger/F-series pet peeves, especially with manual trans 4x4's. The JD's make it disappear and, to me, that improvement alone would make them worth the price of admission.
What is 'slip-yoke bump'? I wonder if this is what I informally have been calling 'slop'?!

How about a random, interesting shot of the installed bars..

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  #15  
Old 07-25-2005
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Looks great Colin. Seems like a ton of work, but I'm glad it makes the truck ride better. I'm still thinking about the Duff bar or a set of Helwig anti-sways for mine.
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Old 07-25-2005
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Again, I still think that MOST of the work is because I have the 31-spline LII axle. Several people have recently posted that w/ the newly redesigned brackets it is just about bolt on for folks w/ the regular 28-spline axles. I guess our u-bolt/spring plates are different. In a normal install all you have to do is drill and mount the front bracket.. oh, and flatten that same front bracket. (Takes all of 5 min w/ a bench vice and a BFH!)

Edit: 'Rev' commented in John's thread about his install. It didn't sound like he had to grind/file the brackets at all. He has the same, newer bracket as I have.


His spring plate looks different. Also the nuts on his u-bolts look smaller, suggesting I'm right about the 19mm nuts for the 28-spline axles.

Last edited by NHBubba_Revisited; 07-25-2005 at 10:50 AM.
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Old 07-25-2005
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Sweet! Congrats on the install! I'd planned on getting a set of Duff's for my truck since I got it, but ended up with the RCD's then the Deavers so I guess that wont happen...

If you want to do a write up that would be great! I have a feeling you have tons of good photos. PM me if your going to do it and I'll send you the How To templete.
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Old 07-25-2005
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Quote:
Originally Posted by NHBubba
Thanks!
What is 'slip-yoke bump'? I wonder if this is what I informally have been calling 'slop'?!
Leaf spring suspension does not precisely control axle housing rotation. It resists it but it is, after all, a set of springs that locates the axle assembly. The axle assembly tries to rotate based on the torque being applied to the wheel/tire assembly, whether braking or accelerating.

There is a spline in the driveshaft that slides to adjust its length as the suspension moves. On a 4x4 Ranger, it is in the driveshaft between the U-joints; On a 4x2 Ranger, it is ahead of the forward U-joint, sliding unto matching splines in the tailshaft housing of the transmission.

When the truck begins to move forward under moderate power, the axle housing tries to rotate opposite of the wheel rotation. As this happens, the low pinion position pushes forward on the driveshaft, trying to shorten it. But the torque across the slip yoke splines tends to resist the slide of the slip yoke. As the truck speeds up a bit, the torque differential across the slip yoke decreases enough to allow the spline to slide forward an inch or so. For a split second, the axle housing rotates and the rear portion of the driveshaft jumps forward to its new position, reducing torque applied to the wheels. This momentary loss of torque to the wheels is called slip-bump.

When the truck is new, the grease on the slip yoke splines minimizes the effect, but later the slip yoke friction increases enough to cause an annoying bump shortly after launch on moderate throttle.

All Rangers have this tendency but it is more prevalent in 4x4's, Edges and Trailheads. These models have factory lift blocks that allow increased fore-aft movement of the axle housing when rotating under the spring pack.

Traction bars channel the axle housing's reactive torque to the frame instead of to the springs. This eliminates the slip-bump by controlling the axle rotation.
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  #19  
Old 07-25-2005
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Quote:
Originally Posted by rngprerunner
If you want to do a write up that would be great! I have a feeling you have tons of good photos. PM me if your going to do it and I'll send you the How To templete.
Send away.

Although I'd love some help from the rest of the board too. Bob already answered my torque issue, and informs me that loc-tight is not needed on the u-bolt nuts. But I would still like to know what size socket is needed for the u-bolt nuts on a 28-spline axle. Whatever I write I'd like for it to be 28-spline friendly, as that is what 98% of the Rangers out there have.

I have 48 photos of the install. Although many are out of focus or not really useful. I put the camera in full-auto mode as I was concentrating on the install and not the photography. Hopefully I have enough to illustrate what needs illustrating though..
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Old 07-25-2005
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I'll get that off to ya..

I can get you the nut size from the 28spline, I still have my ubolts lying around and I can check the torque specs if Bob doesnt beat me to it (have them on comp at home)

Cool deal!
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Old 07-25-2005
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Thanks for the explanation Bob. Sounds like that momentary drop in torque is exactly what I was experiencing. I tend to be well on the power.. or well off. So I suspect that this bump was what I was feeling when I came off the power and/or gave her a hard shift. So far things seem to be better.

I always knew that the axle moved, rotated and bounced around under acceleration. I just never really realized it moved THAT much. I can totally see how a set of lift blocks would exagerate that though..
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  #22  
Old 07-25-2005
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Quote:
Originally Posted by rngprerunner
I can get you the nut size from the 28spline, I still have my ubolts lying around and I can check the torque specs if Bob doesnt beat me to it (have them on comp at home)
He got me the torque spec already (76 ft-lbs). I need to know what size nut is used to know what size socket is required. I suspect it is a 19mm.
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  #23  
Old 07-25-2005
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Quote:
Originally Posted by NHBubba
Again, I still think that MOST of the work is because I have the 31-spline LII axle. Several people have recently posted that w/ the newly redesigned brackets it is just about bolt on for folks w/ the regular 28-spline axles. I guess our u-bolt/spring plates are different. In a normal install all you have to do is drill and mount the front bracket.. oh, and flatten that same front bracket. (Takes all of 5 min w/ a bench vice and a BFH!)

Edit: 'Rev' commented in John's thread about his install. It didn't sound like he had to grind/file the brackets at all. He has the same, newer bracket as I have.


His spring plate looks different. Also the nuts on his u-bolts look smaller, suggesting I'm right about the 19mm nuts for the 28-spline axles.

The 28 spline axles U-bolts on mine are 18mm nuts and the new designed rear brackets dropped right in. However, you will still need to flatten the front brackets for proper alignment. I also recommend using the forward mounting hole in the rear brackets for the traction bar. I know it looks weird in the pics like it might hit the front spring bracket but it has plenty of clearance.

Theres also more pics on my cardomain link
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  #24  
Old 07-25-2005
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Quote:
Originally Posted by NHBubba
He got me the torque spec already (76 ft-lbs).
I ment to say I'll check and make sure the spec for 28 is the same as 31..
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Old 07-25-2005
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Quote:
Originally Posted by rngprerunner
I ment to say I'll check and make sure the spec for 28 is the same as 31.
I got the 76 lb-ft spec from the 2002 shop manual. It makes no mention of a difference between the torques for the U-bolts on 28-spline and 31-spline axles. So I checked the torque for the U-bolts on an 8.8" F150 axle which is just a wider track version of the Level II 31-spline. It is given as 73~97 lb-ft.

So, if I'm interpreting it correctly, the 76 lb-ft torque setting is acceptable for the U-bolt nut torque on either axle.
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