Dana 300 Transfer Case Cover Plate for Lomax 4:1 Kit

If your Jeep CJ has a Dana 300 transfer case and you have geared it down with a Lomax 4:1 low range set, or you are about to, the thin factory inspection cover on the back of the case becomes the weak spot. This MOTOQUEEN cover plate is machined from solid 6061-T6 aluminum to replace that cover, add stiffness to the rear of the housing, and give you a bigger, easier fill plug and a drain plug tucked up out of the rocks. It is aimed at 1980-1986 CJ5, CJ7 and CJ8 owners and anyone who has swapped a Dana 300 into a crawler.

What the cover plate does on a Dana 300

The Dana 300 is a gear-driven, part-time case. Stock low range is 2.62:1, and the Lomax-style kits replace the gear set to get 4:1, which means roughly half again as much torque multiplied through the case in low range before it ever reaches the axles. The inspection cover closes the opening at the rear of the case where the intermediate gear and output gears are serviced, and its bolts help tie that part of the housing together. A heavy plate that bolts to the same location adds stiffness right where the case sees load from the low range gears.

There is a practical sealing reason too. Fitting the larger 4:1 idler gear calls for grinding a small notch in the case, and the RockCrawler LoMax install write-up warns that taking off too much material makes it hard to seal the inspection cover. A thick, flat machined plate with a fresh gasket gives you a better sealing surface than a stamped cover that has been bent or pried off a few times. The kit also swaps the small factory -6 fill plug for a -8 SAE magnetic O-ring plug, so you can check and top off the case with a wrench and the magnet catches gear wear between services. The drain plug is recessed into the plate instead of hanging below the housing.

Signs your Dana 300 needs this plate

• Gear oil weeping from the rear inspection cover gasket, especially after a hard day in low range
• A dented or bent factory cover from rock strikes, or a drain plug that has been knocked or rounded off
• A seized or rounded small fill plug that makes checking the level a fight
• Fine metal paste on the fill or drain plug that you want a magnet to catch going forward
• You are installing 4:1 low range gears, bigger tires or deeper axle gears and want the case stiffened before it cracks

How to confirm before you order

Make sure the case is really a Dana (Spicer) 300: it has the rear inspection cover this plate replaces and, on a CJ, the passenger-side front output. Clean the rear of the case and run the Jeep to see whether the leak is the cover gasket or an output seal. If the case pops out of low range, that is usually worn rails, detents or sliding gear inside the case, not the cover; the Lomax-type kits ship with heavier detent springs for that reason. If the shifter itself is sloppy, our Dana 300 twin stick shifter for 1980-1986 CJs fixes the linkage side.

Fitment

This plate is for the Dana/Spicer 300 transfer case, which Jeep used in 1980-1986 CJ5, CJ7 and CJ8 Scrambler models. It works with a stock gear set or with a Lomax 4:1 low range kit. Many Dana 300s now live in other rigs behind swapped transmissions and adapters, and the cover location is the same, but check clearance to crossmembers, skid plates and the rear driveshaft before you install. If you are unsure what case you have, send us the year and VIN or a photo of the case and we will help. Other driveline pieces are in our hard parts section.

Install notes

• The kit includes the plate, the -8 SAE magnetic fill plug, 10 socket head cap screws and 10 thin washers. A gasket is not listed; buy one and use a thin bead of RTV.
• Drain the case, remove the old cover, and scrape the case flange clean and flat. If the case was notched for a 4:1 idler, check that the gasket still has full contact around the notch.
• Put a washer under each cap screw head and tighten evenly in a cross pattern. The RockCrawler LoMax article torques the inspection cover bolts to 15 ft-lb; stay near that, since these thread into the case.
• Fill to the bottom of the fill hole with the gear oil your Jeep manual calls for, then recheck after the first drive.
• If you have the case apart, replace worn output yokes now; the Yukon 26-spline 1310 yoke for Dana 300 fits the outputs. CJ owners regearing the front axle should also look at the Dana 30 front spindle for 1979-1986 Jeep.

Do I need a Lomax 4:1 kit to use this plate?

No. It bolts to a stock Dana 300 in place of the factory inspection cover. It is designed to handle the extra load of a 4:1 low range, but it works the same on a stock 2.62:1 case.

Which Jeeps came with the Dana 300 transfer case?

Jeep used the Dana 300 in the 1980-1986 CJ5, CJ7 and CJ8 Scrambler. Later Wranglers used different chain-drive cases, so a YJ or TJ only has a Dana 300 if someone swapped one in.

What comes in the kit?

The machined 6061-T6 aluminum plate, a -8 SAE magnetic O-ring fill plug, 10 socket head cap screws and 10 thin washers. Plan on a new gasket and RTV.

How tight should the cover bolts be?

Snug them evenly in a cross pattern. A published LoMax install torques the inspection cover bolts to 15 ft-lb, and that is a good target since the bolts thread into the case.

Will this stop my Dana 300 from jumping out of low range?

Not by itself. Jumping out of gear is usually worn shift rails, weak detent springs or a worn sliding gear inside the case. The plate stiffens the housing and seals the rear; internal wear still needs a rebuild.