Drive Line Angles: Peer Review requested

So I have fallen into the black hole of information regarding driveline angles, safe U-Joint operating angles at certain RPMs, and recommended U-Joint operating angles according to Spicer. I've read articles and forum posts both here and in other websites & forums, and to anyone who is face-palming right now and thinking "Oh good Lord, not another one," please just bear with me as I need a second opinion before I go and devote a few weekends to this.

My '09 Tacoma is experiencing driveline vibrations after having the drive shaft serviced at a reputable local shop here in Denver, CO. Slip yoke and Carrier Bearing were worn out & needed replacement, and we got all new Spicer U-Joints installed while we were there (3 total). Before service, I only felt vibes between & during 25-30mph (somewhat typical), and when letting off the gas pedal to coast at 60mph or higher.

After Servicing, the vibes between 25-30mph feel worse, there's a secondary pulsating vibe at 35mph, and a low, constant vibe anywhere at or above 60mph.

Now most of us here would probably say, "take it back to that shop and have them re-balance it, because something ain't right." Yes, it's likely I will be doing that. But having done my homework, I decided to embark on measuring my driveline angles anyway, as my Taco has a 6" lift on it (4" blocks on the rear) and as a result some not-so-stock angles.

Note: I have already embarked on some adjustment in an attempt to get rid of the bad vibes, but the attached "DriveLineAngles-Existing" image is what I am at currently: After all of my research from both forum posts, Spicer's videos and the use of their multiple Calculators (including the torsion analysis), I've settled on a proposed set of angles, which includes adding a 2.5 degree shim at the leaf springs. "DriveLineAngles-Proposed" is the full layout for that:

So my overarching question is: I'm shooting for making the rear diff angle the same as the first shaft from the transfer case. But i'm worried in that I cannot, due to the carrier bearing attachment flange, get the U-Joint angle at the T-Case any less than 3.5 degrees. The Carrier Bearing Bracket location makes it so my drive shaft would be at 7.0 degrees anyway even if my truck were pure factory. My #1 worry about this setup though - I am not canceling the angles by adding the axle shims. Won't I still have vibe issues at highway speeds even if my pinion angle matches my first coupling shaft?

Any feedback on this would be welcome, There's SO much information out there about this particular issue and I've waded through just about all of it, but I've also heard that theres just as much miss-information regarding this topic. And, as everyone keeps saying, every truck is different, so each solution has to be as well.

Thank you!

 

Well I went ahead and made some adjustments. Worst case was that I could just put it back the way it was, right?

The plot thickens though! After I got everything up in the air, I noticed that one of the iron blocks between the leaf spring and the axle was suspiciously taller than the other. Grabbed a measuring tape and sure enough, the block on the driver's side was installed backwards. I double checked the Installation Instructions for the lift kit to be sure, and yep, both of them should have the short side pointing toward the front. I don't know if it was installed this way intentionally, but to heck with it, I decided to flip that block around and re-measure all of my angles before I add any new shims (Side note - how in the world would a shim on top of a block even work...? The mounting pin isn't quite long enough to engage, i'd probably have to find a way to weld on more material and I don't have that capability).

So with everything bolted back up & torqued to spec, I have new numbers that are suspiciously close to what I was proposing in the first place:

1st DS - 7.4 down
2nd DS - 10.6 down
Rear Diff - 7.0 down

The results after test drive: Low vibration between 25-30mph is now 99% gone (it's very very subtle but still there), and the vibration at 35 is mostly gone but it is still there but is severely reduced. However, the constant low tone vibration at 60mph+ remains, as this may likely be a balancing issue. I'll be taking the drive shaft back to the person who worked on it last tomorrow morning to get the balance re-checked. We'll see what happens.

If it turns out that the shaft is indeed balanced and the low tone vibration is from something else (angles not cancelling, perhaps?), then I'm going to be looking into adding a double cardan joint at the T-case. Some may think this is insane to add a double cardan to a two-piece shaft, but I have no other way to cancel these angles out. Tricky thing there though, I would need to relocate the carrier bearing if I didn't want to have the original shaft cut the same amount that the double cardan adds, just in case this doesn't work either i could go back to semi-stock.

 

I would consider getting rid of the lift blocks before getting a new drive shaft. Look into getting a custom leaf pack that can adjust your angle at the same time. Lift blocks will cause you all sorts of issues with vibrations and axle wrap.

 

OP, a common element that is not given much attention in any of these threads is to make sure the truck is absolutely level before taking any of these measurements. It was the turning point on mine as my supposedly-level concrete garage floor is anything but level, but visually it appears quite level. I went as far as shimming to get front-back and side-to-side level. Suddenly I had new and very different numbers to work with.

Also, take a hard look at the angle gauge you are using. I got and returned several of the Harbor Freight ones because I could not get two to match. Also look at their specs, most of the digital angle gauges have a wide range of accuracy to the point that they have little meaning other than being a gimmick. I also believe that at least two different calibrated angle gauges should be used at the same time to verify the readings. I sort of collect these gauges and can tell you that you get what you pay for with them.

 

I didn't think to consider that, I'll definitely look into it. Kind of a bummer though given I just had it into the dealer to get the leaf spring TSB taken care of, so I have a brand-new set of factory leafs on the truck. Maybe they will fetch a price. I've heard good things about the Old Man Emu's, but I'll browse around. Thanks for the suggestion!

Good point, I am well aware of the flat garage fallacy. I will also admit that I have taken measurements at different times and have gotten slightly different numbers. What I tend to do is I measure each point, then set the measuring device on the concrete to see what my garage's concrete floor slope tends to be and subtract. So far the number has been the same at all the locations though different depending on the day (0.2 degrees one day, 0.8 degrees the other, etc). But given this last round of angle measuring, I am thinking of swinging by Home Depot instead and getting a different angle finder, as I'm currently using the digital square one from HF.

 

This could be fun. Please update and let us know what you discover.

I fought this problem until turning blue and have dozens and dozens of trial and error measurements and diagrams that literally fill several notebooks.

I should add that where you take the measurements is also a big deal IMHO. You will find that small casting imperfections, bits of dirt and grease and trying to fit the gauge on a flat surface can be a problem obtaining numbers that are difficult to repeat. I finally resorted to unbolting the flanges at the transfer case and the differential and measuring the surface of the flanges because they turned out to be the only reliable machined flat surfaces large enough where I got consistently repeatable readings.

I can also tell you that in the end the best solution for me was to stay very close to home with Spicer's recommendations for matching the slope of the rear differential with the slope of the first shaft coming out of the transfer case. The angle of my pinion (differential) flange is 4.4-4.8 degrees and the slope of the first shaft is 4.3-4.5 degrees so this matches Spicer's Fig. 10 of making sure the first shaft and line through the differential are parallel.

 

I'll definitely report back on my findings too, I just got the call from the driveshaft shop & they say they've re-balanced the thing so I'm both excited and anxious as to what the results will be there after I re-bolt it on tonight.

I've also taken measurements from both the U-joint cap (per Spcer) as well as the T-Case & Differential flange. Of course, these did yield different numbers. I simply loathe taking the drive shaft off at this point though. I've considered using the 'Zero at the transfer case flange' method but that still robs me of the true down angle of the t-case.

Your pinion+first drive shaft angle is basically what I was hoping to achieve at the start, with the caveat that the true angle to the T-case would be more than 1.5 degrees. But I gotta know - How in the world did you get that shaft to 4.5???? The best I can do due to the carrier bearing mounting bracket is 7.0~7.4.

Thank you for sharing your numbers, by the way. It helps me a lot to compare notes.

 

BTW, I see you are in Colo. Where did you have the shaft balanced? I had mine micro-balanced at a place in C.Sprgs. and honestly it made no difference and cost me $100, and I can not recommend the place.

I had an aha moment and decided to eliminate all sources of error from where the measurements were taken, to leveling, to getting decent gauges, to replacing the rear transmission/transfer case mount with the TSB one. Afterward I started reading "better" angles. I also messed with the whole carrier bearing shim thing and felt that only a little difference was made. It was not until I read and studied those Spicer documents and the 2014 TSB many times that it occurred to me the TSB is really trying to better match the angles of the first shaft and the pinion, at least so I think. That is why some of the new part numbers for the rear springs have incorporated shims in the bottom leaf. I also rotated the pinion a bit with shims.

 

The shop I went to is called Drive Train Industries, their main shop & headquarters in Denver. They've got a full service shop in that if you bring your drive shaft in already detached from your vehicle they will work on it. Plus they are an Authorized Spicer Parts dealer, so I know I'm getting legit Spicer for the best price. I've since picked up the drive shaft now that it's re-balanced, and while the guy who did the work was out to lunch when I got there, I noticed he removed a balancing weight on one of the shafts. So there must have been some irregularities that he hopefully corrected. I'll know more tonight when I install it & test drive. I'll try to call him this afternoon too to get the full report on it.

I haven't heard of any TSB's for the rear transmission mount though.... Like I mentioned before I brought it into the dealer about 2 weeks ago and the only ones they checked on were the springs, rust inspection, some stock factory wheels issue, and the gas pedal TSB. Rear transmission mount didn't come up... But I will look into that too. If I'm owed a new transmission mount I want it.

 

The mount was included as part of the 2014 TSB along with new parts for the springs, a steering wheel damper and misc. hardware Here is T-SB-0008-14. It first appeared early in 2014 with applicability to automatics. Then Rev. 1 appeared in July of the same year and that included applicability to the 6 speeds as well.

 

Wow, thank you for sharing that, I remember reading this now.... I wonder why they didn't bother to look at this one when I had it in at the dealer. My guess would be since the suspension isn't stock they overlooked all of this.[EDIT: I just saw on that PDF that it says "If the vehicle has an aftermarket suspension/budy lift or leveling kit installed, this bulletin does NOT apply". so yeah, that's why] It also could be that I'm beyond the factory Powertrain warranty (Truck is certainly beyond the 60 month mark).

Anyway! I have a few more results. After the rebalance, vibrations are now much more subtle. No vibes at all past 20 mph, and then a subtle one at around 60 mph but then goes away again when i drift up past 65. So that definitely was a factor. I do have a shudder under acceleration from a stop till about 10/15 mph though. I would chalk this up to the non-cancelling angles of my diff vs my driveline. I'm still very curious/interested in adding a double cardan or 'H' yoke at the T-Case. According to spec sheets, it will add 2.66 inches to the drive line, which i think I can make up for in the slip yoke without issue. Last thing to worry about is relocating the carrier bearing with a custom bracket. I'll design something that works and is sturdy. Either that or I start playing with putting spacers/washers back in like the carrier bearing drop mentioned in so many other threads.

Taco'09: What points did you measure to when you were making sure your truck was level before doing the drive line angle measurements? did you put the angle measurer on the frame rail? Somewhere else?

 

I should have elaborated a bit. I did not measure the angles relative to the frame or any other part on the truck. Rather, I do my own wheel alignments and that requires the truck sit on a level surface both back-to-front and side-to-side. Since my garage floor is anything but flat I made shims to place under the tires so that all wheels (tires) then sit on a level surface, albeit one that is created by shimming. For measuring the drive line I used this same method. I have to jack the truck a bit to get shims under the wheels so I use DIY slip plates (a couple of 1' X 1' sheet metal shims with grease between) for the rear. This can also be done for the front if needed in order to let the suspension settle as the truck is then lowered back down to sit on the shims.

I then measured the absolute angles of the drive shaft flanges at the Tcase, rear diff, and the shafts themselves. Many angle gauges will measure absolute angles when first turned on but its a good idea to check that has not been set otherwise. Like I said I disconnected the shafts from the flanges (block the tires!!!) at the Tcase and rear diff so as to get nice large machined surfaces to measure. Its also real important to always keep the angle finder in the same plane (this is also addressed in the TSB) and not doing so can be a critical source of errors.

 

Heya Taco'09, not to beat the dead horse but, how do you know that the truck is purely level if you didn't measure from any part of the truck? I fully understand your method, I've used the same slip plate strategy when trying to measure & adjust my caster (only I used two 12x18 sheets of 1/8" MDF, worked great), but won't you need some sort of base line to measure against? Or was it your garage floor you measured, and then calculated how big your shims needed to be based on those slopes?