[crossfire876]

The 96 Cobra is making a loud whirring/humming noise which sounds like it's coming from the differential. It only does it at certain speeds, but is constant at those speeds as long as I'm pressing on the gas pedal. Makes me think the ring and pinion are bad.

I've never opened the rear end of this car, personally didn't matter to me what gear ratio was in there as long as it ran well, but since my gas mileage is horrid and I'm at about 45mph in 5th gear, it makes me lean towards 4.10s or 4.30s. (Suggestions?)

I'm not interested in racing this car in any way, I'm just looking to maintain and enjoy the car for what it represents. For this reason, I plan to replace with the stock 3.27. I can buy used ones reasonable but am I asking for trouble doing so?

This car has also been lowered, not sure how much, but would guess 1.5'', would like to replace the stock springs while I'm at all this, but not sure if the original owner cut or replacing the original springs, not sure how much of a project they will turn out to be.

Last question, can all this be done with floor jacks? Or, being a novice weekend mechanic, should I only buy new gears and trust this installation to the professionals? Got a guy here that said parts and all to replace, drain, and refill gears would cost me right at $650. (Reasonable?)

[97_4V_Sleepa]

Get a buddy to help you do the gears that knows what he is doing, Buy NEW GEARS, and Yes you can do it all as a Novice with a a jack and jackstands. I do have a recommendation though, go with at least 3.73 gears. It will help you accelerate on the on ramps and give you a nice pass ability on those pesky 2 lane roads that seem to have the slowest driver in the world on.

[crossfire876]

Originally Posted by 97_4V_Sleepa Get a buddy to help you do the gears that knows what he is doing, Buy NEW GEARS, and Yes you can do it all as a Novice with a a jack and jackstands. I do have a recommendation though, go with at least 3.73 gears. It will help you accelerate on the on ramps and give you a nice pass ability on those pesky 2 lane roads that seem to have the slowest driver in the world on.

I've heard that from quite a few people now, will be buying new gears.

Rethinking a few things,

Originally Posted by Ford Mustang Tech 4V Cobra: The Cobra has an entirely different engine than most people are used to. It performs best at high rpms, upwards of 7000. It's power band is relatively high due to the deep breathing nature of the two intake valves. When gearing a Cobra, 3.73's just aren't enough. They don't allow the engine to reach its powerband quickly enough. 4.10 gears are an excellent choice and 4.30's are even better. This may sound very steep if you're used to the average 5.0 which needs to be shifted by 5600 rpm. But since this engine will easily rev to 7000 it needs the extra gear and it likes it. 4.30's are our #1 choice, naturally aspirated or supercharged. At 80 mph in fifth with 4.10's the engine only turns about 2700 rpm, completely tolerable.

Is there anyway to make reasonable power and boast 15mpg city and 20mpg highway? Can you do that w/ 3.73s and 4.10s?

What else should I replace while I'm digging around the ring and pinion?

Any advice appreciated

[tango7]

I had 3.73 gears in my 01 cobra and got about 19 around town and 22 hwy.. You can do the gears.. I would get ford racing... You should get bearings,and rebuild the limited slip unit while you have it apart.

[crossfire876]

Originally Posted by tango7 I had 3.73 gears in my 01 cobra and got about 19 around town and 22 hwy.. You can do the gears.. I would get ford racing... You should get bearings,and rebuild the limited slip unit while you have it apart.

been looking for a little literature to walk me through the repair, but can't what I'm looking for. Want to replace ring and pinion, all bearings, and possibly the limited slip.

[cobraetti]

I didn't attempt the 4:10's in my car (IRS)

I do also get the whine at certain speeds

[noslow5.0]

I would put your car up on jack stands pull the ebrake up a little to get a load on the rear end and have some one go through the gears in your car while you are out side to see if you can pin point the noise. I know at lower speeds in first and second gear my tranny will whine a little. Also i have 4.10's in mine and i really like them, and my gas mileage is still pretty decend, once i get my turbo on and tuned i will probably go to some 3.73's.

[OldSVTGuy]

Anything is possible. However, if you are a novice, I would highly recommend you have a pro do it. I had to have my rear gears replaced on my '92 5.0 under warranty and THEY did it wrong and had to do it over. At a minumum, you will need a depth mic and a dial mic to measure pinion depth and backlash. If you don't know what I'm talking about, and I'm not meaning to bash you at all, then you probably should not attempt this. You will also need a press to remove and replace the pinion and differential bearings. Setting up a rear end is not an easy job. I might attempt it but I've been working on cars for 45 years but would still have to get a dial micrometer. Whining from the rear end that has never been modified and is fairly high mileage, TYPICALLY, is bad pinion bearings (I've had 'em).

Good luck with your project but I think you should re-think doing this yourself. You might check to see if you have a bad axle bearing - that could make noise, too, but it is typically on one side. Since you have a SRA, labor should not be that much for removing your rear cover and doing this work. Labor for an IRS rear is MUCH higher.

[crossfire876]

Originally Posted by OldSVTGuy Anything is possible. However, if you are a novice, I would highly recommend you have a pro do it. I had to have my rear gears replaced on my '92 5.0 under warranty and THEY did it wrong and had to do it over. At a minumum, you will need a depth mic and a dial mic to measure pinion depth and backlash. If you don't know what I'm talking about, and I'm not meaning to bash you at all, then you probably should not attempt this. You will also need a press to remove and replace the pinion and differential bearings. Setting up a rear end is not an easy job. I might attempt it but I've been working on cars for 45 years but would still have to get a dial micrometer. Whining from the rear end that has never been modified and is fairly high mileage, TYPICALLY, is bad pinion bearings (I've had 'em). Good luck with your project but I think you should re-think doing this yourself. You might check to see if you have a bad axle bearing - that could make noise, too, but it is typically on one side. Since you have a SRA, labor should not be that much for removing your rear cover and doing this work. Labor for an IRS rear is MUCH higher.

A bad pinion bearing was my first guess, seeing as usually they're the loudest and protest the most out of the entire rear end when going bad. I don't have a whole lot of support w/ expert advice around here. The guy that is thinking of repairing it with me is an auto-school dropout. With that said, I think the previous owner of the cobra put 4.10s or 4.30s in here, just from judging my RPMs in various gears, although no idea.

I did manage to get my hands on a decent pinion depth gauge and bearing pullers, but this would be, at best, a look at pictures repair and try to figure things out as I go. With that said, beauty school dropout is the one that's convinced the ring and pinion is shot, however I"m not, I've thought pinion bearing since day one. But if the previous owner did a 4.10 swap, or hell 5.xxx swap in his garage, it could be his shotty mechanics skills I'm replacing.

I got up under the rear end, and the pinion seal seems fine from what I can see. No gear oil slung around the differential and the "bleeder valve" for lack of a better word, on the axle is clear. Didn't take off the drive shaft so can't tell you if the pinion itself is loose.

The car makes it's whine only when I press the gas petal, and only at certain speeds, when the whining noise starts it progressively gets louder and raises in pitch as the RPMs increase, but immediately stops if I take my foot off the gas. When I press on the gas again, the pitch is the same. The noise sounds like it's coming from the right rear of the car.

Btw, no offense taken. I am a novice mechanic at best. I understand that some repairs I can do myself and others I cannot, but the only decent shop around here I've found wants anywhere from $350-600 in labor just to take it apart. Thought at first they were quoting me on an IRS, but was told they knew it was a SRA, and that an IRS would be at least double that. Still sounds a little steep for me. Thus spurring me to try to do it myself.

Maybe you can diagnose the issue better than the advice I'm getting around here.

About forgot, the engine has 92,xxx miles on it (probably hard earned, since the car is lowered and guessing 4.10s w/ a short throw shifter), and the speedo doesn't work. Took the speed sensor out and the little plastic Recalibration Gear is chewed to hell. Not sure what to put back in it because I have no idea what rear end gears are in the car.

[OldSVTGuy]

$500 for just labor on an SRA seems high to me. All you have to do is pull the inspection cover off, take out the little lock nut, pull the c-clips and then the axles let go. After that, it's four bolts to take out the differential and one big nut on the pinion and it comes out. That is maybe an hour's worth of work. The disassembly, removal of bearings doesn't take that much, either. Re-assembly does take longer. You might check with others, but most have said they've paid from $175 - $225 for labor.

The increasing howl could also be a bad backlash set up - too loose - from a previous install. It's all done with shims and it isn't always right the first time. If you use FMS gears, MAYBE you could get away with the same pinion shims but you need to take a depth measurement on the head of the pinion gear to the top of the differential case before it is removed, while it is still bolted in. You can start with the stock shims on the ring gear as a starter to see if your backlash is OK.

There's a lot to it and it would take me quite a while to get it right. Check with some Mustangers in your area and see who they use for gear swaps - you might get a better price somewhere else and just as good a job.

Good luck.

[crossfire876]

Originally Posted by OldSVTGuy $500 for just labor on an SRA seems high to me. All you have to do is pull the inspection cover off, take out the little lock nut, pull the c-clips and then the axles let go. After that, it's four bolts to take out the differential and one big nut on the pinion and it comes out. That is maybe an hour's worth of work. The disassembly, removal of bearings doesn't take that much, either. Re-assembly does take longer. You might check with others, but most have said they've paid from $175 - $225 for labor. The increasing howl could also be a bad backlash set up - too loose - from a previous install. It's all done with shims and it isn't always right the first time. If you use FMS gears, MAYBE you could get away with the same pinion shims but you need to take a depth measurement on the head of the pinion gear to the top of the differential case before it is removed, while it is still bolted in. You can start with the stock shims on the ring gear as a starter to see if your backlash is OK. There's a lot to it and it would take me quite a while to get it right. Check with some Mustangers in your area and see who they use for gear swaps - you might get a better price somewhere else and just as good a job. Good luck.

Thanks for the help. If I the ring and pinion and this master install kit, is there anything else the mechanic/or I might need? Or is this kit a little overkill?
Ford Racing 3.73 Gears $150

Master Install Kit $110.95

Master Install Kit $110.95

[OldSVTGuy]

That kit and the gears should be all that is needed; other than RTV sealant for the rear cover. A lot of mechanics like to get your parts for you as they get a mark-up. Maybe that's why the guy wanted $500 labor. You only use the crush collar once you are sure your pinion is at the right depth. The shims for the pinion depth are UNDER the bearing so you have to take the bearing off/on a couple of times to get the depth right. Thus, the need for a press and bearing separator.

FMS gears are much more consistent in their maching than other gear sets. Many guys can use the same pinion depth shims and be pretty much on the money. Backlash, with new differential bearings might be a bit different. \

Oh, did they give you any marking grease? You use this on several ring gear teeth to ensure that the pinion contact on the ring gear is correct. I hope you can see from the things I'm advising you that you can understand that installing gears has to be done very precisely. Otherwise, it can make very loud whine noises or, actually, blow up on you if the backlash is set too close. And, if it is NOT done correctly, many mechinics will give you ANY reason why the set up is correct and something ELSE happened. They hate to have to re-do their work and own up to a screw-up.

Best of luck to you!!

[crossfire876]

Originally Posted by OldSVTGuy That kit and the gears should be all that is needed; other than RTV sealant for the rear cover. A lot of mechanics like to get your parts for you as they get a mark-up. Maybe that's why the guy wanted $500 labor. You only use the crush collar once you are sure your pinion is at the right depth. The shims for the pinion depth are UNDER the bearing so you have to take the bearing off/on a couple of times to get the depth right. Thus, the need for a press and bearing separator. FMS gears are much more consistent in their maching than other gear sets. Many guys can use the same pinion depth shims and be pretty much on the money. Backlash, with new differential bearings might be a bit different. Oh, did they give you any marking grease? You use this on several ring gear teeth to ensure that the pinion contact on the ring gear is correct. I hope you can see from the things I'm advising you that you can understand that installing gears has to be done very precisely. Otherwise, it can make very loud whine noises or, actually, blow up on you if the backlash is set too close. And, if it is NOT done correctly, many mechinics will give you ANY reason why the set up is correct and something ELSE happened. They hate to have to re-do their work and own up to a screw-up. Best of luck to you!!

I really appreciate all the help. Made sure I repped you for all the advice you've slung my way.

I've decided that it's worth the time to do this right, so I'll let a professional do the work. It's always the easiest to take advantage of somebody who knows nothing about what they need, so I'd like to be as knowledgeable as possible before requesting parts.

Doing research on FMS gears and many others share your opinion. They fit well and are easier to install, because something to do with pinion size or something like that. However, I can't seem to find anywhere that sells what I'm looking for.

Learned that true FRPP gears have been made by Motive in the recent past, and have heard many horror stories of Motive gears whining, regardless of setup.
M-4209-G410A- Genuine Ford Racing Gears
M-4209-G410M- Gears made by Motive for Ford Racing

Originally Posted by Self-Proclaiming Expert For what it's worth the date which motive began manufacturing the 4.10 geaarset for Ford was 11/05. My installer who is a Ford mechanic does 50-60 gear sets a year. I have driven in many cars the year before in which he has done the gear installs and have never heard a set of his gears whine. I had it done by him late March/early April as soon as the car came oit of storage. These were the M4209G410M instead of the M4209G410A As others have stated they are made for FRPP by Motive and have a backcut on the ring gear. After installing them we went for a road test and the whine on decell was insane. To make a long story short he setup the gears 3 times and didn't charge me any more than if he did it once but the whine was still there. We happened to pull a set of older FRPP 4.10's out of my friends 03 GT 1/4 mile car which had about 50 runs on them and threw them in and no more whine.

Originally Posted by Rick Hey guys my name is Rick I am the Mgr of Downs Ford Motorsport. The M onthe end of the part number means they werebuilt by Motive gear. I have also had issues with whine noise's. What I been doing is having anyone who purchase's the gears with M at the end of the number go onto Motive gear site and download the motive gear install instructions they seam to differ from the Ford set up a little which I have found makes the difference so their is no Whine from the rear. Any question feel free to call me at 1-732-349-2240 ext 958 ask for Rick

It's just a rumor at this point, but seems like a lot of individuals are blaming Motive instead of the installer, so I figured it was worth considering.

Ran across this looking for FMS gears, worth considering?
Sketchy "New" Gears with 1 Mile on Them?
for $100, my budget begs me to at least consider them. Will these OEM 3.55 gears install without much issue?

I think I have some gear marking grease somewhere in my garage, I'll have to check.

Thanks again for all the help.

[97_4V_Sleepa]

Ran across this looking for FMS gears, worth considering?
Sketchy "New" Gears with 1 Mile on Them?
for $100, my budget begs me to at least consider them. Will these OEM 3.55 gears install without much issue?

I think I have some gear marking grease somewhere in my garage, I'll have to check.

I wouldn't buy them personally. to me its not a matter of how many miles, its a matter of "did some asshole drop this on the floor after he heated it up with a torch to get it off". IDK that's just me.

[crossfire876]

Originally Posted by 97_4V_Sleepa I wouldn't buy them personally. to me its not a matter of how many miles, its a matter of "did some asshole drop this on the floor after he heated it up with a torch to get it off". IDK that's just me.

I agree. After the research I've looked into, the money I'd save picking up used gears just isn't worth it. I'm still thinking it's just a pinion bearing, but while I, or the mechanic if I chose, is in the rear end I might as well put the gears in I want. Not sure if I want to pay to tackle the limited slip or not yet, guess we'll just see.

The guy that's supposed to be helping me swap this out hasn't called me back, so it's quickly turning into a solo project.

Now I just got to figure out what to pick up, 3.73s or 4.10s...I want the 4.10 kick, but at the same time, my highway commute at 70-80mph worries me.