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Discussion Starter #1
First off, I should have put this gear in to begin with. I ran around with 3.73's for quite some time, and they suck. This is a good gear for this car. In all honesty It might still be a little tame. Anyway The install went well, backlash is set up a little tight, .0035 to be exact, but ford specs are like .004-.008 so I figure it should be ok. pinion depth is perfect, the pattern looked great. They are completely silent through accel, cruies, and deaccel, but I've noticed an odd vibration/noise in fifth gear at high speeds. I don't know exactly what speed, (I'm still fighting with my damn speed cal. See speed cal thread.) But based on the RPM I'd say it's around 90-110 MPH. It's a rythmic vibration/noise, and it goes away in the triple digits as the speed increases. The sound is sort of a "womp..Womp..." with vibration. It's not to pronounced, but I notice it. It doesn't coincide with any rotating machinery on the car, as it cycles at about 2 times per second at the above mentioned speed. Almost like a road noise, only I've tried many different roads. In all honesty I've heard/felt this prior to the install, but not as pronounced and it may have gone away. (or I got use to its frequency or something.) Either way, now it's back

Other than that, (and the speed cal debacle) I'm pretty happy. traction in 1st is a problem, but that was expected. 5th is far more usable than with the 3.73's. The car seems to sound different, too. Like higher pitched or something. Of course that makes sense as it's running through the rpm range quicker.

All in all no one should fear this gear in this car. I wouldn't want them with a blower, but for an N/A car they are just fine. It's not nearly as radical as one might think.
 

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See, I knew you would like the 4.30's. This is what should be in the car to start with.

I think everyone is used to the old 5.0's and they think this gear is radical when, in all reality, it is not for the DOHC.
 

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I hate to say this, but .0035 is WAAAAAY too tight. IDK where you got your .004-.008 spec on the backlash, but the proper specs are .008-.014. I'd get that changed before you mess it up, going 100+ at that tight of a backlash has probably hurt it already.

James
 

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I"m going with the 4.30's after I see what I can do on the 3.73's with my DR's...need to save up some $$$ too first...

What is your RPM at around 70mph???
 

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I get that same noise you describe with my 4.30's. I have been unable to diagnose what is causing it. Thought maybe pinion angle, but just not sure. Mine starts about 75 and last through about 85 where it starts to taper off. Only problem is thats the interstate speeds I like to travel, and the noise can become quite anonying with the windows up.
 

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Discussion Starter #7
IslandVobra said:
I hate to say this, but .0035 is WAAAAAY too tight. IDK where you got your .004-.008 spec on the backlash, but the proper specs are .008-.014. I'd get that changed before you mess it up, going 100+ at that tight of a backlash has probably hurt it already.

James

Yes, you are right. Ford Specs say .008-.015. Those specs I had came from some non Ford book. Should I do them again? I doubt that could be causing my noise. They are pretty damn quite otherwise. I really don't feel like tearing that thing apart again. What could happen if I leave it? Overheat the gears, sieze the bearings, what? I could get it right in the middle of the specs, I'd just have to get a .005 shim.
 

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Discussion Starter #8
LR 01 Cobra said:
:) Try indexing your drive shaft, that might help with the vibe! I love the 4.30's

Tim:evil:
What exactly does that mean? How do I do this?
 

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Discussion Starter #9
missouri_guy1973 said:


What is your RPM at around 70mph???
2640 RPM with stock tire height. Not to bad at all. In fact 80 is only 3000 RPM. The secondaries don't open untill over 90. (My secondaries, anyways. Mine open at 3500 for some damn reason. Maybe its the chip?)
 

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Hmmm, with you saying those RPM's I think I might actually have 4.10's in my car (Don't know what it came with when I bought it)...my RPMs are a little lower than what you are saying you have with 4.30's...GOnna go change the settings on my Speedcal and test it out...

--edit--

Nope...they aren't 4.10's...all my speeds were too low...guess they are 3.73's or 3.90's?!?!?
 

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What you're experiencing is "driveline vibration" caused by higher rotational speed of the driveline. You can either try to rotate the driveshaft in 90* increments and see if it improves, or install an aluminum shaft, which may help - it may make it worse, too. :)

Todd
 

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lo pony said:
What you're experiencing is "driveline vibration" caused by higher rotational speed of the driveline. You can either try to rotate the driveshaft in 90* increments and see if it improves, or install an aluminum shaft, which may help - it may make it worse, too. :)

Todd
Granted it could be it but the driveshaft I have is balanced down to 2/10th's of a oz. and I have the noise he describes. So I think it's something different then that. I also have CNC'd rear pinion so I know it's not the runout.
 

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Discussion Starter #13
How does one go about getting a driveline balanced? If the noise/vibration isn't from the driveline, what else could it be?
 
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