The DDD: OFFICIAL Diff Drop Debate! + PIC/s

[00_4runner]

Hey guys just wanted to pick some of the brains that we have on the forums regarding something that most of us use in our lift kits: diff drops.

Now I'll start off by saying that I have the Toytec Ultimate Lift, 600lb red coils and 5150s with 891s in the rear. When I first installed my lift I had some serious driveline vibrations from about 55+ mph. Yes I did put in the diff drop that came in the kit. Like most everyone else I did not question the need for it and since Toytec included it in the kit, I installed it. I had to fix the vibes fast because they were strong enough to feel like a massage chair through the entire car. My 'temp' fix has been to lower the front coilovers (I have massive rake which I hate!). So first question is: can a diff drop cause vibrations due to changing the suspension geometry further?

Now I'm not gonna pretend that I'm a driveline guru or that I completely understand the geometry/angles involved with the system. However I have been doing a good amount of reading and research which seems to point to diff drops ultimately being unnecessary. Yes we all know the claim that they prolong CV life, BUT the drop seems to put the front diff at an angle that affects how oil gets to the components, AT THE SAME TIME it changes the driveline geometry, which may be, at least partially, the cause of my vibrations (I installed my coilovers at the preset height that they from Toytec ~3 in).

This gets more complicated than what I have described, which is why I'm hoping to get some responses from the more 'driveline-inclined' haha. I know that Singtoe does not run any diff drop and from the projects we've seen him do I think its safe to say we can trust his opinion. Recently I was looking through Dirtco's build and I saw that he had new upper control arms installed on his rig, which changed the angle of the driveshaft (assuming for the better). I hope that one of you guys can chime in here and help out, to be honest I'm pretty confused!

Also before anyone says something about "oh well the diff drop is cheap insurance, just spend the 40 bucks, you'll save your CV boots" I have to say that I did not start this thread in order to save a few bucks, but more so to help myself/members understand the need, or lack of, for the diff drop kit. I really want to do my lift right, and if possible prolong the life of the suspension and driveline parts as long as I can. No vibrations would be nice as well!

Driveline 101
-This is a link about the basics of drivelines for anyone who is interested or wants to learn a little bit more about how angles/suspension geometry works.

I'm also adding this picture from a post by CSL, in which he took two pictures, a before and after, showing the very small gain in CV angle after installing a S.S. diff drop. It features one picture superimposed over the other to show the difference (which isn't much!).

LET THE DEBATE BEGIN!
:vader:

 

[PhdNPrerunners]

My post probably isn't going to be much help but I don't think the vibration has to do with your diff drop. Im running the Tundra TRD Coils and Bilsteins on the 3 notch with no vibration what so ever. I installed my diff drop right before I drove from California to Texas and the whole drive I did not have any vibration at all with speeds up to 95 mph. I have run diff drops on all of my toyotas with no vibration problems at all.

 

[lpittman]

Did you get an alignment done after you installed the lift? The lift can change the camber (caster? ... ugh) by a few degrees sometimes, which could cause some odd behaviour.

 

[00_4runner]

My post probably isn't going to be much help but I don't think the vibration has to do with your diff drop. Im running the Tundra TRD Coils and Bilsteins on the 3 notch with no vibration what so ever. I install my diff drop right before I drop from California to Texas and the whole drive I did not have any vibration at all with speeds up to 95 mph. I have run diff drops on all of my toyotas with no vibration problems at all.

Thanks for the reply but I think the vibration is kinda hit and miss. Most 4runners don't get it, some do. I haven't seen too many 4runner with the problem but I came across some diff drop info and thought that maybe the diff drop could have caused it. I know, I know it does not make sense that only some 4runners have my issue and some don't but that's what it looks like. Probably has something to do with how they were driven, maintained, how 4WD was used. I stumbled upon some info and it got me thinking. But like I previously said, some of the more mechanically inclined guys like Singtoe don't use the drop at all, and have no issues.

Did you get an alignment done after you installed the lift? The lift can change the camber (caster? ... ugh) by a few degrees sometimes, which could cause some odd behaviour.

Haha yes I got an alignment. I've had multiple alignments, something like 6-7. I have done A LOT of work, especially lately that would require an alignment, so I know for sure that is not an issue. I tried everything, you name it. The only thing that fixed my vibes was lowering the coilovers. I know of a few others here who were experiencing the same issue, but people don't really post about it. I'm pretty sure I saw Ripcord write something in his build not too long ago about his issues with vibrations. Maybe some think its normal, idk. But I have seen a couple threads. I believe Haddix had the same issue at some point as well.

BUT this isn't a thread to really help me diagnose my vibrations. I made it more as an information source (about how a diff drop works, if its really necessary, or maybe its actually bad), not only for myself but also for the other forum members who are having a hard time finding info.

I hinted at the few members whose attention I was trying to get with the thread. Singtoe, Dirtco, Gerdo, BFAD is always a great source of knowledge not to mention a few others. Come guys, help us all out!
:biggrin2:

Plus maybe this way we can save a few threads being posted about the same topic again.

 

[Yoter]

I know, I know it does not make sense that only some 4runners have my issue and some don't but that's what it looks like.

Just a thought, could it be the various gear ratio's? Maybe only one ratio is susceptible to these issues.

I dont have a diff drop yet but am planning on installing one sometime in the next week I am very interested in seeing how this will play out.

 

[Harleydoc]

My think are you feeling the vibs in the steering wheel if not I think I Would look at some other thing maybe a bad u joint. I have a buddy that has a bad vib in his runner right after the Diffy drop. A few day later took out the drop still had it he throw a bunch of parts at it till one day I drove it and told him I thought it was a u joint so I check out the drive shaft and it ha all kind if slop in her.

 

[nobb]

Bumping an old thread as it appears the OP started the thread with a great topic but little discussion seemed to result from it. It would be great to have a thread with consolidated info on the diff drop debate based on unbiased technical reasoning rather than opinions or anecdotal experiences.

From my understanding:

Pro diff drop:
Lower CV angles resulting in less wear on the joint and the boot due to stretch. However, I dont think I've read any instance of anyone with a CV joint failure other than a leaky boot due to additional stretching.

Against diff drop:
- Increased diff angle causes less lubrication on pinion seal (no evidence for or against this).
- CV joints can better take an increased angle than U-joints (in the drive train).
- Driveline geometry between transfer case and front differential is now non-stock. The U-joints in the driveline are now under additional stresses and the pinion is not straight causing possible vibrations.

I would be interested in hearing more thoughts on this last point. It seems to be more than just coincidence that some people have experienced driveline vibrations after doing a diff drop.

 

[afg10000]

I've experienced no vibrations or abnormalities with the diff drops. The only problem I incurred was broken boot seals. CV joints seem fine. The seals failed due to angle increase then decrease during lift installation. The angles looked pretty dramatic when we put the truck on the ground after coilover install. Looked a lot happier after diff drop. My thought is if the parts have been well maintained and seen little abuse, perhaps it doesn't matter diff drop or not.

 

[Singtoe]

Over the past year, there have been documented front diff failures. All of them with Diff drops.


Coincidence or is it that those who wheel with diff drops, wheel harder than those without.


Here is a fact.

The diff drop is not a diff drop, it's a diff droop. Lowering the front of the diff only lowers the the half shafts 3/8 of an inch.

Other facts. The front diff is oiled using a splash system, with oil level sitting right at the bottom of the rear pinion bearing.

1 When your lower your front diff, the rear pinion bearing is running dry.

2 When you check or change your diff oil. The Oil fill is sitting lower than stock and you are actually putting in less oil than the factory specs.

3 The drive line angles for the front drive shaft is altered. Once the ujoint angles get out of phase with each other, the pinion will speed up and slow down with rotation of the drive shaft.



The rear driveshaft has a double cardan joint (constant velocity) so the rear pinion angle is not as critical.

Now for opinions

Anytime that lift is done and changes the regular working angle of the cv boots, something will happen. Stretching and articulation of 15 year old rubber will do something.

If you can prevent the bellows of the boot from touching or rubbing on them selves, you can improve the life of the boot. Google "streching 4runner Boots".

Getting tighter clamps can help with grease leakage.



My Opinion. Lowering 3/8 of an inch not worth the loss of the front diff.

There has been about 4 front diff failures throughout the last year and every single one of the had a diff drop.

Front Diff Carnage

WOW. (front diff carnage)

used front differential?

Diff Carnage...



Plus, $40 plus S/H for two bolts and two spacers is postponderous.

 

[nobb]

With a splash type lube system, I wouldnt expect the differential to be as sensitive to oil level. If it is a concern, you could always put the truck on ramps and "overfill" the front differential slightly.

Your 3rd point is what I would be most concerned about.

If I had to choose, I would rather put additional stresses on the CV joints and boots than grenading the front driveshaft/differential.

 

[curtperry]

LET THE DEBATE BEGIN!
:vader:

I got tired of seeing the bad overlay job in this pic so I took my own pics today (taking my diff drop off for now). This is with 3 inch front lift. It looks a little more dramatic when the pics are done right but it's still not a huge difference.

Just better info for those trying to decide...

50% opacity comparison:

 

[00_4runner]

I got tired of seeing the bad overlay job in this pic so I took my own pics today (taking my diff drop off for now). This is with 3 inch front lift. It looks a little more dramatic when the pics are done right but it's still not a huge difference.

Just better info for those trying to decide...

50% opacity comparison:

Hmm, thanks for posting this! I might consider taking mine out now.

Are you still running your drop??

 

[FancyPantsMcGee]

I think the only correlation between broken front diffs and diff drops is this: owners who droop the diffs, also lift the suspension and add big tires.
I've never heard of anyone having a diff drop, without also having a lift and bigger tires. so a straight cannot be drawn.
In addition; people with said modifications are more prone to abuse their trucks off-road. (that's the idea anyway)
.. do I dare say; folks with lifts/tires/diff drops who go off-roading are more likely to experience front diff failure? :drum:
The links to broken diffs clearly show the trucks were being "well-used." It also leaves out any sort of condition/mileage/maintenance the diffs had been subjected to. except the crazy driving around in -34..
I know the one I posted had seen some serious driver ineptitude.
I have a diff drop on mine, I have no intention of taking it off.

 

[Singtoe]

My taco has 37's on it with 3" suspension lift. I dog the hell out of it. I pull trailer anchors out of the ground with it. Go door deep though mud with it. Load it full of scrap metal to get recycled, load it full of top soil and Yet I have no diff drop on it.

I have my 4runner which I baby, while I am harder on my truck then most because I treat it like a tool. The truck is awesome. I have no lockers on it but because of the tires (height), it goes everywhere.

 

[BigRogers]

I have no idea if the diff drop was truly the culprit here but I had my front pinion gear get destroyed. I have since re-geared but will be removing my front diff drop and doing a CV boot stretch instead. Just for the simple fact that I would rather keep the drive shaft angles at factory specs and have a higher CV angle instead.

For what it is worth I asked the gear guys at the shop if the diff drop could have been the reason for the failure but they said it was more than likely just flat out bad luck that it failed. They didnt seem to think the DD did any harm to the gears.

 

[curtperry]

Hmm, thanks for posting this! I might consider taking mine out now.

Are you still running your drop??

Yeah it might be worth putting the pic in the top post... feel free.

Not running my drop right now.

 

[00_4runner]

My taco has 37's on it with 3" suspension lift. I dog the hell out of it. I pull trailer anchors out of the ground with it. Go door deep though mud with it. Load it full of scrap metal to get recycled, load it full of top soil and Yet I have no diff drop on it.

I have my 4runner which I baby, while I am harder on my truck then most because I treat it like a tool. The truck is awesome. I have no lockers on it but because of the tires (height), it goes everywhere.

Thanks for chiming in!

From what I'm hearing, I might have to take mine out. The difference really seems to be negligible and I need to learn how to swap CV's anyway, so let them leak!

Now on to see if longer rear uca will finally allow me to get 3" out of front suspension without vibration...

 

[Coast2Coast]

I didn't read all the posts here but look into this. I've seen people get this same vibration issue and seen them replaced tons of parts in the front end, only to finally replace both front CV axles which cured the problem. They showed no sign of being warn but were in fact warn just enough to cause a vibration. Hope this helps.

 

[Coast2Coast]

Sorry I forgot to comment on the diff drop debate part. I never used a diff drop on my 09 taco with 3" lift and it saw 100,000km of 50/50 offroading/going to work. The truck saw some pretty violent offroading in its day before I sold it. Never had any issues. I won't be putting a diff drop in my next taco that I'm picking up this fall.

 

[ryanpavelchik]

The ujoint point makes the most sense