I need some opinions on this on fellas.

I need larger gears in my 75 bronco (9 inch and dana 44).
My new nv3550 transmission has overdrive, and I have 36 inch
tires, so I figure 4.56 rings will be just right.

My question is, do you think I should do it myself?

I have most of the tools such as a dial indicator and torque wrenches, and i've read the tech articles. I also just rebuild my
Dana 20 transfer case, but never tackled a diff.

Any advice or experience is appreciated.

 

Hello.

Go for it. I just finished building the rear end in my '73. It was the quite frustrating at first. Getting the right parts and trying to understand some destructions the company had gave me. Just take your time and put everything back where you got it from and all should be well. So far I have been driving for two weeks on my first rebuild and no problems. The dana 44 is still waiting for the same treatment... I'm not tackling that one yet until help arives later this month. So for now it's a 4x2 73 bronco.

Duane

 

You'll need a bearing press, and you'll be pulling them off/pushing them on a LOT.

 

to do it right it would be best to have a pinion depth gauge also. depends if you have someone you know that can do it right in your area. those new gears are not cheap to buy. i have done them before but if i have time there are some local experts i prefer to have them done "right" by them. pinion depth and back lash need to be exact and he sure makes it look easy for the amout of time i keep putting it together and taking it apart.

 

Go for it, it is easier then it sounds. Do the Rear first, it is easier, and you can do it all on the bench. Use red lip stick, it works better then marking compound. You only have to press the pinion bearing on one time.

The hardest part in the whole thing is tearing down the front end to get your axels out, which isn't too bad.

 

IMO, I have seen numerous DIY differential jobs. The majority of the time, they end up bringing it in on a tow truck unfinished or broken. Or driving it in with the gears howling so loud that even the radio won't drown it out.

Yes, setting up a ring and pinion isn't rocket science and it can be done with little know how. But to set it up correctly...
The difference between a ring and pinion set up that will run for a long time and not make noise and one that will burn up in 20 minutes is only a couple of thousandths of an inch.

If I haven't dissuaded you yet, heres a couple of pointers.

The 9" is probably the easiest differential to set up. You set your pattern pinion depth with shims in the pinion housing. The back lash and carrier bearing preload is set with adjustable spanner nuts at each side of the carrier. And pinion bearing preload is set by a crush sleeve. You will need a dial indicator with a magnetic stand or clamp, a inch- pound beam or dial torque wrench, spanner wrench, a 1/2" air gun, a bearing puller and press (which can be done by a local shop if you don't have the facilities). I would recommend new bearings at the same time. And this is the perfect time for a locker or limited slip.

An ideal pattern is centered on the tooth, but slightly toward the toe. But in the real world, it doesn't always happen that way. Sometimes you go back and forth with adjustments and get the best compromise you can that will be as quiet as possible. Also stick with reputable gear companies. I have had good luck with
Motive Gear Performance line for the 9", and I try to use OE Spicer ring and pinions for the 44's.

While the 44 is different in setup procedure, the idea is the same.
You set pinion depth with shims behind the inner bearing race. The thicker the shims, the farther away the pinion is from the ring gear. Backlash and carrier preload is set with shims on the carrier under the bearings. Pinion bearing preload is set with shims instead of a crush sleeve. Normally, I like to start out with the original shims that were in the diff. This will get you in the ball park to fine tune your pattern.

Also, you do not need a case spreader to work on the 44. I have found that the carrier can be removed easily with a prybar and a box end wrench on a ring gear bolt to keep the carrier from turning. To install the carrier, I angle the bearing races toward the inside to start them. And then, I go back and forth on the carrier races with a brass hammer. The carrier should go in pretty snug, but not hard enough that you need your biggest hammer to make it go. This will tell you that your carrier preload is ok.

Millertime,
Red lipstick, huh? Does it have to be cherry red or would dark rose be suitable?

Jason

 

ever see someone use a pinion depth tool? on the end of the pinion it is stamped what depth the pinion should be in at. you install the pinion without any shims and the tool measures the depth. then you take the recomended depth off of the pinion and subtract the depth without any shim. that gives you the thickness of the shim you need. put the shim in and reinstall and there it is.

 

Pinion depth tools are nice for setting up a bare housing where you have no shims to use as a baseline. However, the markings on the pinion are for Dana use. Most of the aftermarket gearsets that I have used for the 44 (or any Dana axles) do not have the pinion depth setting. But even with the pinion depth tool and factory markings it will still only get you in the ball park. They don't take into account housing wear or differences in bearing manufacturers tolerances.

FWIW, the shop that I work at builds over 250 differentials a year. We do not even have a pinion depth tool in the shop.

Jason