12 replies to this topic

[Straight6]

Should a person who has no experience working on differentials attempt to change the ring and pinion on the front diff? I have an 83' bronco with a 9". I have worked on motors, removed transmissions etc... but nothing with differentials. I am trying to go to a higher gear ratio.

[sweepersrgr8]

NO! although the setup on the front is not as crucial as the rear, since it is not in use full time. The improper setup could ruin a new set of gears quickly. I have seen folks that just use marking compund to set their gears, but I feel more comfortable using my dial gauge, and mics along with the marking compound. That way I know it is set to specs, and will last through the trails.

Also your front gears should match your rear within a few tenths, or you could trash your transfer case.

[highboy73]

i'd try it if i were you,they make directions for everything.take your time and do it right don't be afraid to ask for help.
you do need some tools for setting pinion depth and backlash,if you can read you can do it.
good luck

[Seabronc]

I go with NO . You can't just wing it. You also need special tools to get it right. You will spend the money over again if you don't set it up right .

Good luck,

[Seabronc]

Actually, I take back some of what I just said, the NO part. That is a conditional no. It sounds like you have some mechanical ability and experience, so If you are willing to go out and buy the proper tools, follow the proceedures in (preferaably a Ford shop manual), Go for it . Go for it.

Good luck,

[Straight6]

where would I get the proper tools and can they be rented? I'm trying to save a buck or two.

[Seabronc]

You may be able to rent them at a place like AutoZone, but I actually doubt it. Unless you know someone who has them, the tool cost might make it worth having a 4x4 shop do it. Why did I say 4x4 shop? Well, unless you know the guy you are dealing with and have confidence in his ability and that he uses the right tools, you might be better off winging it.

Here is an example of things you need to know, From the 83 shop manual;

Note: When changing ratios on the 44 Series front drive, it may be necessary to change the differential case along with the ing and pinion.

The front drive procedure isabout 6 pages long including Figures and charts. the tool list is a page and 1/2 a few of which could be improvised.

If you really think you want to do this, I could copy the pages and mail them to you. The one nice thing is you can do a 9 inch rear axle on the bench. Personaly, I would take it to a 4x4 shop. I say that because they sholud already have the tools.

Good luck,

[freak]

A pinion depth gauge and a carrier spreader make it easier but once you've done so many you kind of just know what to expect.You'll need a dial indicator to check your backlash.I did my Bronco myself many moon's ago and I had never done it before.I just talked to alot of people and read alot of article's.Now it seem's like everyone want's me to set up their's.I use to do it one the side but you get some people who want to blame you for everything even though you tell them to make sure there's no metal left in the axle.Make sure you clean everything really good,metal left in the axle will kill bearing's and if it's big enough it will ruin you gear.

[Straight6]

OK, after reading all of the replys and looking thru my toolbox it is starting to look like it might be less expensive to have someone else do this for me, so much for saving a buck or two.

So now that I am heading in another direction I need a little more advice. This Bronco is an 83' with an inline 300 cid carbed w/4 spd OD manual (rug trans), it has 3.00:1 ratio gears in the diffs. This is a project and will not be my daily driver but will be used on the deer lease, beach and the occasional mud hole if I can find one here in Houston and therefore needs to be street legal. Here is where I need the advice. I am going to keep this Bronco sane, and just change the tire size up to 31's and put limited-slip units of some kind in both diffs:

1) What gear ratio should I be running? (The rear diff needs to be rebuilt anyway but the front is fine so I think I can just change the ring and pinion to match whatever I put in the rear.)

2) Would I be better off buying a rear 3rd member from a place like Randy's or a used one from a place someone recommended to me?

Any and all suggestions would be helpful.

[freak]

I would switch to a 4.11 or a 3.73.On the front if you go higher than a 3.73 you have to get a smaller carrier.

[Seabronc]

Freak is right, 2.72 - 3.73 use a thick differential case flange and and a thin ring gear, 3.92 to 4.56 use a thin case flange and a thick ring gear.

Also don't forget as you go up in ratio your RPMs to maintain highway speed say 60 MPH, increases. That is offset some by your OD but still something to keep in mind.

Dynatrac use to have a reat article on their site, but I looked for it and it doesn't seem to be there anymore. I have a print copy of it. They give the following formula to pick the right gear ratio:

RPM = (336/Tire Diameter) x MPH x Gear ratio

You can also find this on pg 30 of Jeff's bronco graveyard "80 and up catalog". along with a chart calibrated at 55 so if you normally do 65 for highway cruise, you need to redo the math.

The charts don't consider you using overdrive, they are written around a 1:1 drive which is your 3rd gear ratio. I believe your OD is .7:1 but still pick gears based on the 1:1

The Dynatrac article is quite comprehensive and goes into pros and cons of the different kinds of lockers and their use. Also they cover when you should upgrade to DANA 60, etc. All I can find on their site is details about their new stuff. They don't seem to support the 44 any more on the site.

http://www.dynatrac.com

Good luck,

[Straight6]

OK after shopping around for a 3rd member I am back to rebuilding the rear and changing the ring and pinion on the front myself. So, where can I get a book on rebuilding diffs or can I get a Ford manual that will tell me how to do it?

[Seabronc]

Well, it is a fairly large section in one of the Ford shop manuals. Check ebay for a shop manual for your year truck though the proceedure is the samefor them all. So if you get one for any of the 80'sit will have what you need. I only say get one that is the same year as your truck is if you are going to spend the money on it, you might as well get one that completely matches. You will need the, "Body Chassis Electrical" manual Volume A, it's about 2" thick. If you don't see it advertised, email one of the guys that is selling on that site and ask if they might have one that is not advertised yet.

Good luck,