DIY differntial gear change... reasonable?

[cowger]

As many have done, I'm ready to change the gears in my '05 vert from stock to 3.55:1.

I'm not entirely opposed to paying someone to do this, but I really enjoy working on my own car and am trying to assess the difficulty of this job as a DIY. I was hoping the factory service manual might have something on how difficult this job is, but as you know it just states that the entire diff is serviced as a unit.

For anyone who has done this themselves, I'd like to hear your thoughts...

Thanks!
Bryan

 

[gb66gth]

Ask mjorgensen. I think he said something about, once the car has been driven any real distance it becomes significantly more difficult to get it apart.

 

[TowDawg]

If you're swapping a complete new assembly with the gears already installed, it's not too bad (assuming nothing is "stuck" together). GB is correct that the miles on the car can play a significant role in the difficulty, as the halfshafts can seize onto the diff splines over time.

If you're talking about opening up the rear end and changing the gear-set yourself, that might be a little tougher. I've heard the Viper gear-set is not the easiest thing to get right, but that most experienced off-road shops can do it correctly.

I took the easy way and ordered a whole new diff assy with a Quaife and 3.33's already installed by Unitrax.

 

[mjorgensen Woodhouse]

The Gen3 cars come apart easy at any mileage. I did my own gear change (first ever for me) and it went smooth and never had a problem. Getting the pinion depth and pattern right take some finesse so it helps to have a bench and diff holder because it is out of the car. Chances are though if you don't have access to a shop I would let the pros do it for you, the rear end of a Viper sees a lot of forces and you don't want it wrong.

 

[Sonoman]

What mjorgensen said. If you don't have some experience with gears it could save you a lot of labor down the road by removing the diff and taking it to a rear end shop. Also, don't buy low cost ring and pinions... get the OEM Dana/Spicer or better. If you know someone that has experience with gears maybe they could help out and give advice on the finer points. But this is really something you don't want to do twice, and if you do chew up a gear, the resulting debris can take out much of the rest of the diff. I personally would have a tough time trusting a diff that was assembled by a first-timer, especially in a high-torque hotrod. Certainly it is possible to do it yourself-- a friend of mine pulled it off on his 450 HP Mustang, but he did a lot of studying beforehand and had all the right tools. So if you're a guy who pays a lot of attention to details and precision, you might be a good fit for this kind of job. I weenied-out and paid Unitrax to do it for me, and even then I was paranoid about it for the first 500 miles.

 

[roller]

What mjorgensen said. If you don't have some experience with gears it could save you a lot of labor down the road by removing the diff and taking it to a rear end shop. Also, don't buy low cost ring and pinions... get the OEM Dana/Spicer or better. If you know someone that has experience with gears maybe they could help out and give advice on the finer points. But this is really something you don't want to do twice, and if you do chew up a gear, the resulting debris can take out much of the rest of the diff. I personally would have a tough time trusting a diff that was assembled by a first-timer, especially in a high-torque hotrod. Certainly it is possible to do it yourself-- a friend of mine pulled it off on his 450 HP Mustang, but he did a lot of studying beforehand and had all the right tools. So if you're a guy who pays a lot of attention to details and precision, you might be a good fit for this kind of job. I weenied-out and paid Unitrax to do it for me, and even then I was paranoid about it for the first 500 miles.

Well said, setting up a Dana requires tools and knowledge of correct bearing preload and pinion to ring gear centerline distance, and correct backlash.

Frank

 

[bluesrt]

yep, as long as you have no howl noises- you got it right- if you have howl noises after install, stop right there and have a pro set it up,because you have the tolerences off..

 

[Paul Hawker]

Setting up a diff is as much an art as science.

Put it together too loose, and it is weak. To tight and it is noisy.

Go to someone with lots of experience, such as Unitrax in SoCal for a quiet, long lasting diff.

Fresh diffs have a break in period of around 500 miles. Drive a bit (50 miles) and let it cool down, then drive again. If you can have fresh oil changed out after 500 miles or so, you will get rid of all the break in gunk, and should be good to go for thousands of miles.

 

[Black Moon]

If you're going to swap the entire unit please PM me. I put 355's in my gen 3 last year and have decided to sell it (for the right price) and have a gen 4 built with 333's. As far as swapping the ring and pinion yourself I'd pay a professional. I watched mine getting done and it's a ton of work, especially if you are changing all the bearings which is always reccomended. The tools that you'll need will probably cost you more than the labor unless you borrow them.

 

[Ratical2]

I talked to the Wizard about this last year. He told me that by the time I buy the tools to do the job right, I might as well pay a pro to get it done right...

 

[cowger]

Thank you, all, for jumping in with some great advice. The consensus seems to be that it's too tricky and expensive (tool-wise) for a good DIY project and too critical a component to be done wrong.

My next question is then: What's a fair price for a reputable shop to do the swap?

Thanks again! Love this forum...
Bryan

 

[Black Moon]

I spent $225 but I know the owner pretty well. I've heard prices from $250- $900. It depends on whether you bring them the car or just the differential. You could pull it yourself and save several hours labor.


Don't scrimp on the rebuild and buy the master' rebuild kit which has all the bearings, races, seals and gaskets. You also need new axle bolts and straps from Dodge. Dodge says to change them.

Changing the bearings adds to the cost which could be why some people paid so much more. It took my tech as long to change the bearings and seals as it did to set up the gear. Then there are gauges and a special jig involved so the pinion gear is set up and shimmed outside of the case before it's installed. If this is done correctly everything is perfect when it's all done. I forgot the settings but it's like between .0015 and .003 for the gear to be in spec and not make noise.

Good luck.