christoffer

Hello.

Got my diff brace from bonzai racing today.

After install, it is alot of vibrations above 5k rpm:s

I had some problems with the install, the holes in the chassie dident match the holes in the brace. Got it in place with some violence.

Can my old diff bushings be the problem or is it something with the ppf.

My mods are:
-Bonzai motor-mounts
-Engine damper

I have bought new diff bushing, not fitted yet.

/Christoffer

MrNizzles

iTrader: (5)

what sorta violence? maybe the driveshafts are not aligned correctly now (diff twisted in its position) and are torqeing somehow at certain rotation speed .. ??

might try removing it and see how it drives then...

I would be interested to know too

redrocket1

iTrader: (32)

Same thing happened to me after i installed a tomei 2 way lsd and the banzai diff brace. It makes a whining sound around 5k rpm +. But i dont have any wheel hop and i dont go above 5k unless iam sideways drifting then you really cant hear **** besides tires screeching. IMO it sounds kinda cool.

christoffer

I had to move the diff forward and left to make the holes match, brace/chassie.

when the bolts in the chassie is in place, the studs from the diff aint in the middle of the holes.

Is it some one that can explain how to adjust the ppf? dont understand the workshop manual that good.

After uinstalll the brace, the vibrations disaperd.

/Christoffer

Banzai-Racing

iTrader: (11)

Install the new diff bushings that you have. You should not have to force anything into position, but since ou were able to move the diff, that means the bushings are allowing way to much play. Adjusting the PPF is just a matter of loosening the nuts at the trans end. Also loosen the engine dampener so that you are not preloading the engine/drivetrain to one side of the vehicle. Where is the vibration coming from? What is actually rattling?

christoffer

Going to install the diff mounts today. The rattling comes from the rear, the same feeling as when the prop-shaft is unbalanced. the hole car is shaking. Everything feels good under 5k.

Is it posible to mount the new bushings then loosing the nuts to ppf on gearbox, then mount the brace in place to place the differential in right possisition, then tighten the nuts to ppf?

Thank you! this help is very apreciated.

matty

i have the same issue with my diff brace (banzai). dave at kd installed it. he had to bore the holes out wider to get it to fit. i get a slight vibration above say 6500. initially it was worse but now its only slight. my car is low mileage and very well kept, there is nothing wrong with my diff. dave said "it is common to bore the holes out". however alot of guys say that with this brace it should be a perfect fit however that wasnt my experience.

at first i was going to remove it as i felt some vibration even lower in the rpm range at first. it either went away or i got used to it. the vibration isnt bad just annoying as my car has always been a very clean feeling ride. it doesnt make any noise just can feel it in the seat alittle. when going wot i can def feel it still. just doesnt feel as clean.

what do u think banzai?

christoffer

Same here. I had to drill my holes out to make it fit.

I am not afraid of the vibrations, but if it has to much vibrations its not worth it.
Will give it a try again now after i have installed the diff bushings.

Banzai-Racing

iTrader: (11)

The holes are all laser cut and the braces are all welded together on the same fixture, so there is very little variance between parts. I have personally installed hundreds of these and have never once had to open the holes up and have not heard of anyone having to do it before it was mentioned in this thread. That being said, cars do vary slightly in tolerances, automotive manufacturers allow certain levels of slop. As for any vibration or noise, I would have to ride in the car to determine what the actual source of the vibration is. The brace is not the source it is the conduit. We have installed these braces on cars with as little as 10K original miles, and there was no increase in noise or vibration, with all OEM components. However as with upgrading anything in the suspension there is going to be additional stiffness, this is what it was designed to do. If you have sloppy bushings, shocks, pillow ***** etc, it is possible that these could be brought to the forefront after installing the diff brace. I have just never experienced it.

Or is the installer didn't bother to read the provided instructions 7. If the side-arms of the brace do not meet the body mounting locations on the chassis, then your PPF is out of adjustment. Please refer to page J-59 of the Factory Service Manual. You will need to loosen the nuts at the transmission end of the PPF to make the necessary adjustment.

http://www.banzai-racing.com/diff_br...structions.htm

christoffer

Update:

Installed my new diffbushings today.
Mounted the brace again but had to open upp the holes a little to make it fit.
Now i havent any vibrations at all, and wheels dont hop either.

So dont put a diffbrace on if your diffbushings are ****.

Banzai-Racing

iTrader: (11)

We have always said that a diff brace is not a replacement for bad bushings or a cracked PPF. It is not an either/or situation. You need to have good diff bushings along with the brace, they serve different functions.

matty

got it tks

rallimike

iTrader: (1)

KDR had to expand one hole to get mine to fit as well. The brace totally eliminated wheel hop, but it does transmit a whine into the car, and there is a vibration @ around 3800 rpm that you feel in the seat. We tried rubber washers, then bushings, but they didn't help much.

christoffer

I like the whineing, feels like you are driving a racecar now.

matty

now they coming out of the woodwork


banzai, given the fact that some of us have this vibration my question is are we hurting anything? as in damaging the diff. what about slowing us down?

by the way i am not knocking this unit. my guess is banzai is 100% correct and our diff is out of spec. in dealing with them i believe 100% that they are one of best vendors for our cars. u can tell in this thread alone....these guys care. so tks

Banzai-Racing

iTrader: (11)

I hardly call 2 people "coming out of the woodwork". It seems that both of you had your braces installed at the same place. My guess is that it was installed in the same manner, improperly. Jack your car up and see what is going on. Adjust the PPF if needed.

There are hundreds of people on this forum that do not have any issues at all after installation.

The OP has already determined that the issue was the diff bushings not the brace.

rallimike

iTrader: (1)

No need to be defensive, evrything mechanical is a trade-off.
Dave at KDR recommended your part- (you should be nice to him since he sells your stuff commission free.) He said it would cure the wheel hop, which it did. He also said some people have resonance issues, some don't. Makes sense to me that if you bolt something that has moving parts directly to the body, those vibrations are going to be transmitted to the body. How could it be otherwise?
As to the hundreds of people with no issues... my guess is most are running a variety of mods that already create such a din that they wouldn't notice the whine and vibrations.

Banzai-Racing

iTrader: (11)

I am not defensive, the facts are that the installer is the common denominator. Dave does not sell our parts, we do.

If you have a vibration there is something else wrong with your car that needs to be addressed. The moving components of the diff are not in contact with the brace.

Do you really think I would tolerate driving around in my FD with a bunch of vibration at any RPM? I have a huge variety of mods and no vibration would go unnoticed.

joe1573

iTrader: (14)

I installed my diff brace after installing diff bushings, toe link and trailing arms. There was no added vibration from the diff brace that I could tell and it installed very easily with no problem or modification.
I wonder if the fact that the diff brace is being modified would maybe be the cause for the vibration. If you bore open the holes on a wheel it will not spin balanced, right. Just a thought Im not an engineer, please don’t attack.
I guess my point would be if you are having a hard time installing or if there is vibration after; there is more than likely something else that needs to be fixed. Once you get it all tide in, there is no better feeling then a solid launch with on wheel hop.

TRWeiss1

iTrader: (20)

Not to revive an older thread, but I as well just recently installed the banzai diff brace and am now getting intermittent vibrations about 4k rpms. I'm going to talk to Dave @ KDR tomorrow about it, but my guess is that the bushings are probably shot....****ing *****, especially because i'm going to the track tomorrow.

Meh, screw it...If she breaks she breaks!

FWIW, I had to drill out the 2 holes on the driver side as well...didn't fit at all...Dave said he has to drill them out....A LOT...

Banzai-Racing

iTrader: (11)

Hmm? I wonder what is going on out there? We install these braces in nearly every FD that comes into our shop, and if I ever had to drill any holes out I would have fixed the issue. It seems there is a correlation between the fitment, worn out diff bushings and the vibration. We know that replacing the diff bushings eliminates the vibration, I wonder if it also eliminates the need to open up the holes? I am not opposed to changing the programming to open the holes up 1 or 2mm, but I would like to keep everything as tight as possible if it is not necessary.

TRWeiss1

iTrader: (20)

^ I don't think it's your brace man...at least not in my case...My car's got almost 100k on it, and I tracked it some last year (and I do drive it hard regularly ).

I'd be more willing to bet that my diff bushings need replacing.

What's odd though is that it doesn't always do it! This morning on the way into work hammered the gas a couple times through 2nd and 3rd, and voila, no vibration....It has moods....Then again, it IS an RX-7!

Anyway, do you guys think I'll be safe to launch it at the track tonight? I'm debating not going if I shouldn't launch it...

Red95FD

iTrader: (3)

I had my brace installed by Chris at Banzai and it seems to me, if I remember correctly, that he had to raise a sagging diff and drive shaft to get it to fit. It was just not in alignment which I would think that it should be. He had to raise the diff and shaft up abit and then the brace fit fine. Everything does feel tight now. There is a small whine. No vibration but a feeling of tightness. I have wondered if that tight feeling was really something in a bind. But if the whole setup was out of alignment to start, putting it right would be putting it in a bind. My car had 8K miles when it was installed. I agree that every car is different. That's the nature of our cars.

My question is, if you drive these cars with the whines and vibrations, I would like to know what is the weakest link here? the gears?,the transmission?, or just the bushings?

Chris, you checked out my diff bushings, they were OK. Were they under any kind of bind compared to before and after the brace? Am I right about the sagging diff and shaft not being aligned?
Not to beat a dead horse but this is interesting that most are fine and some are not. I would like to know what is different in these problem cars.

Banzai-Racing

iTrader: (11)

Rick- your PPF was out of alignment, which I remedied when we changed your clutch. There is nothing binding in your car. I have driven your car and there is no noticable whine (and certainly no vibrations) that I could detect.

TRWeiss1- I would say that you are much better off launching with the diff brace installed then you were all the other times that you went to the track without it. I can't gaurantee that everything will be fine, I have never seen your car, and the only things I know about it are what I see in your sig

Red95FD

iTrader: (3)

I didn't know you aligned the PPF(you probably told me but I was excited to get the car). My car drives great, I wasn't complaining. Maybe the whine I hear is just normal gear noise. It is mostly in 1st gear accelerating or decellerating.