Yikes, $1500 is a lot for that operation.
The first thing that needs to happen is to find out what your current gear ratio is. Some of these cars came with a tag located under one of the 10 rear cover bolts and looks like this:
That tag goes missing often and somewhere around that time, Chrysler quit using them (so no worries if your tag is missing).
The next step is to remove the differential inspection cover and look for stamped numbers on the ring gear. The stamping will give you the part number (blue arrow - not important), the ratio (in a x.xx format, red circle) and date the ring gear was made on (white line).
With the cover off, see if you have a limited slip carrier. If you have one, then see if yours is sill working. Personally, I DO NOT recommend rebuilding any Chrysler rear differential without installing limited slip (too many advantages and almost no disadvantages (except for cost)). For friends or family, I WILL NOT build one without limited slip.
Chrysler 8¼” differentials (all) came with the following ratios:
2.2, 2.4, 2.7, 2.9. 3.0, 3.2, 3.5, 3.7, 3.9 and 4.1. Most FMJ's used 2.2, 2.4, 2.7 and 2.9.
I like to leave off the last digit off because sometimes the actual ratio varies over the years. One example is 3.21 (45/14) and 3.23 (42/13). In this case, the 0.02 difference is not worth arguing about (you will not be able to notice it).
The 3.0 (43/14 = 3.07) was only used in Jeeps, but will fit into any rear Chrysler 8¼”.
The reason I ask on current gear ratio has to do with your existing carrier. If you have a 2.2 or 2.4 and plan on going to anything else, you WILL have to replace the carrier, as well (another good reason to upgrade to limited slip).
For general street drivability, I recommend 2.9, 3.0 or 3.2. 3.5's are fun if you plan on city only driving. The 2.9's in my '77 318 wagon is also fun (but not as much as 3.5's), but I do a lot of highway driving with it.
I just purchased a set of 3.0's for my '86 Fifth Ave. The 2.2's in it is like dragging a battleship anchor behind the car at take offs
I can literally drive a couple circles around.my '86 Fifth Ave from a takeoff, with my '77 wagon (both equipped with stock 318 2 bbl's). The only difference is 2.2 vs 2.9 gear ratio.
Note: all Chrysler rear 8¼” ring/pinion gear sets will interchange. That said, the front (4*4) differential gear sets are reverse cut will not work.
The bearing kits might depend on what year your vehicle is (possibly).
The carriers have a small difference on axle spline count ('68-96 are 27-spline, and '97 and newer are 29-spline). If using an open carrier (not limited slip) and your existing spider gears are fine, then that will not matter). Most limited slip carriers, the spider gear sets were not made to be interchangeable.
If you change the differential gear ratio (or tire diameter) then your speedometer gear will need to be changed as well – but that is for a different topic.
If you lived closer to me, I would say come on down and bring a 6-pack. We could get the gears changed out one afternoon and you would be back on your way. There might be others in the area willing to do the same – but I can't comment as to who. I would look for a Mopar club in your area and ask around.
Changing rear differential gears is not that hard of a job – but it is a huge help to have someone there who has done it before to either show you how its done, or to supervise.
One last thing, If you are planning on some very hard driving (ie: clutch drops, neutral slams and so forth) where the rear differential will see a lot of hard and sudden impacts like that, I would also recommend getting a crush sleeve kit (using metal shims to replace the crush sleeve). If you just plan on normal driving on a /6 or 318 2-bbl, then the normal crush sleeve will work fine.
Normal crush sleeve
Aftermarket crush sleeve elimination kit.
You have to remove both rear axle shafts to perform any differential work, Check the axle shafts where they make contact at the axle bearings (and axle seals). If you can catch a fingernail at either surface, then you will also need to replace the axle bearings (arrows).
Until recently, you had to also replace the axle shafts, but the aftermarket has came out with new bearings that contact a different area of the existing axle – which is very nice.
Note: it does take a slide hammer and a special tool to extract the old axle bearings.
A person might be able to rent this (maybe).
BudW
