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Chris Calhoun (aka Beefy)
1979 Jeep CJ5

Stock Specs

Engine: AMC/Jeep 304
Transmission: Tremec T-150 3-speed
Transfer Case: Dana 20 2-speed
Front Axle: Dana 30
Rear Axle: Model 20

Both stock axles are narrow track, geared with 3.54:1 ring and pinion gears, 5 on 5.5" wheel bolt pattern, disc brakes front and drums rear.

Dana 30

7.5" ring gear
1.16" 27 spline shafts

The CJ Dana 30 used in '76-'79 CJs came with the preferred 6-bolt locking hub design as opposed to the later 5-bolt design. Dana 30s are fine for most mild to moderate applications, but as with any axle assembly the larger the tire used, the lower the gears, the more power applied, the more likely they will break. Add to that mixture a locker, and you are starting to push the limits. The most common source of frustration is the small U-joints connecting the stub shafts to the axle shafts.

Model 20

8.875" ring gear
1.25" 29 spline shafts

The Model 20 rear axle used in '76-'86 Jeep CJs has a two piece axle design. The hub is pressed onto the axle shaft and held in place by splines on the shaft that cut into the hub. Also a key-way cut into the shaft and hub, and a metal key placed in the key-way to theoretically keep the hub from spinning on the shaft.

The Model 20 has gained a bad reputation mainly based on the two piece axle design. Other potential problem areas are the relatively thin axle tube walls, and short flange area where the tube meets the carrier housing. Although there are some fixes for these problems, these short comings must be factored into the decision to either fix the problems or go ahead and swap the axle assemblies out for something that better suits your needs.

Toyota axle swap

Only Beefy could tell you exactly why he choose this solution, but I can comment on my thoughts and opinions for a little reference.

One of the main problems with this particular year of Jeep is the gearing. Most vehicles come from the factory appropriately geared for the tire size installed, and for the usual pavement pounding. Rarely do we see a vehicle produced with gearing installed for off-highway use (rock crawling etc.).

Beefy's Jeep has a final crawl ratio of 21.5:1. From what I have seen this is the worst crawl ratio (final drive ratio) that Jeep ever produced. The T-150 is 2.99:1, the Dana 20 is 2.03:1. Multiply the transmission's 1st gear ratio by the transfer cases low range, and then multiply that by the ring and pinion ratio and you have the crawl ratio.

In deciding how to modify axle assemblies or doing axle swaps, one must always take gearing into consideration. There are different factors that come into play such as how you use the truck, tire size, and $$$.

There are no magic formulas as everyone is different, and what meets one person's needs may not work for another. In this case, Beefy is getting a set of 4.10:1 gears relatively cheap as they come stock in most mini-truck Toyota third members (differential carrier). That is certainly something to consider when choosing an axle upgrade or swap.

The 3.54:1 gears Beefy's Jeep has are common to this era of stock CJ axles, and lower (higher numerically) gears for these axles are usually only found in the after-market. Factor in the cost of new R&P (ring and pinion) gears, and the labour involved in installing them (shop rate can be as high as $500 for both axles), and things start getting pretty expensive quick.

Buying a set of Toyota axles for a couple hundred dollars starts sounding even better when you consider the comparative strengths of the Toyota axles to the stock CJ assemblies.

Both the front and rear Toyota assemblies utilize 8" ring gears, and 1.31" 30 spline shafts. The rear axle is one piece as opposed to the two piece Model 20 design. The third members (or centre chunks as some describe them) are interchangeable front and rear. If a ring or pinion gear breaks, in most cases it would be cheaper and easier to just buy a new (used) third member and swap it in. With the Dana and corporate axles you would need to buy a new (or used) R&P (and possibly related parts), and have them professionally installed (if you didn't know how to do it yourself...and you BETTER know what you are doing when it comes to this kind of work or get a pro to do it for you).

Along with larger diameter shafts (and R&P in the front), the Toyota housings use a more rigid housing design that tapers from the center section into the axle tubes.

The Toyota axles use a different bolt pattern than Jeeps. You will have to say bye-bye to your old rims because the Toyota rims are 6 on 5.5". The good news is this is a very common rim size shared with GMC/Chevy trucks.

So if 4.10 gears are good enough for your application you may want to investigate this swap a little more, and consider it for your Jeep (or similar light weight vehicle). There are always going to be pros and cons to any modification like this, and we will delve into that a little deeper at a later date.

This swap is being performed while Beefy (Chris) is away at sea doing his duty for our country. I am putting this page up now as requested by John Barron so that Beefy can see what is going on with his pride and joy!

The Toyota axle swap is being performed by John's crew at E4 Auto Repair in Duncan...

More to come soon, and John will have his take on the swap to help inform not only Beefy, but others who might be considering a similar modification.

So far written by jo-jo