PAI EE06720 Differential Lockout Body Kit – Eaton DS340/DS380/DS400/DS402 Forward Axle

The PAI EE06720 is the differential lockout (DCDL) body kit that rebuilds the air-operated lock mechanism on Eaton single-reduction forward (front) tandem axle differentials, replacing Eaton 34779 / 034779. When the dash DCDL switch is energized, air pressure shifts the sliding clutch to lock the wheel differential for maximum traction; this kit restores those internals so engagement and release are clean and leak-free.

Signs You Need a New Differential Lockout Body Kit

• Diff lock won’t engage when the dash switch is activated
• Diff lock stays engaged after the switch is turned off
• Audible air leak from the lockout cylinder housing
• Intermittent or delayed lock engagement

Specifications

Cross References

This kit replaces or is equivalent to the following part numbers:

• Eaton: 34779, 034779
• Navistar (International): 266783, 266783C91

Applications

This differential lockout body kit fits the following Eaton forward (front) tandem axle differentials:

• Eaton 34DS, 38DS
• Eaton DS340, DS341
• Eaton DS380, DS380-P, DS381, DS381-P
• Eaton DS400, DS400-P, DS401, DS401-P, DS402, DS402-P
• Eaton DS451, DS451-P

Representative tandem-axle vehicles using these differentials:

• Freightliner FLD, Classic, Columbia, Cascadia, Coronado
• Kenworth W900, T600, T660, T680, T800, T880
• Peterbilt 379, 389, 386, 388, 367, 579, 567
• International 9200, 9400, 9900, ProStar, LoneStar, LT
• Mack CH, CL, Vision, Pinnacle, Granite, Anthem
• Western Star 4900, 5700XE
• Volvo VNL, VNM, VHD

How the Differential Lockout Works

Air pressure at the lockout cylinder moves a piston and shift fork, sliding a clutch collar into engagement with the differential case. With the lock engaged, both wheels on the axle turn together — maximum traction in mud, snow, or loose surfaces. When the switch is released, a return spring shifts the clutch out of engagement and normal differential action resumes.

Engage the diff lock only at low speed (under 25 mph) and never while a wheel is actively spinning — loaded engagement with one wheel spinning will chip or shear the clutch teeth. Verify your axle model and serial number before ordering.

Handling Time
At All Pro Truck Parts we do our best to ship all orders the same day for orders placed before 12:00 PM Central Standard Time. Same-day shipment is never guaranteed. For standard UPS shipping, you will typically receive your package in 1 - 5 business days. Shipping times are never guaranteed and All Pro Truck Parts is not responsible for lost or delayed shipments by the carrier. Carrier times vary by distance from shipment origin and may change without prior notice. Shipping price is calculated from package dimensions and weight. Calculated rates for orders will be available at checkout. Orders placed after 12:00 PM CST on Fridays will not be fulfilled until the following business day, Monday morning barring a holiday.

Next Day Air Shipments
The cutoff time for UPS Next Day Air is 12:00 PM CST. Orders for Next Day Air placed after 12:00 PM CST will ship the following business day.

Incorrect Shipping Prices
All Pro Truck Parts reserves the right to cancel any order in the event shipping rates are calculated incorrectly at checkout. We will notify you at your provided contact information to give you the option to pay the correct amount, or allow you to cancel the order for a full refund.

Shipping Destinations
All Pro Truck Parts ships within the United States only. We do not currently offer international shipping.

Damaged Shipments
All Pro Truck Parts is not responsible for damage that occurs in transit - responsibility for damaged shipments lies with the carrier. However, we are glad to assist by filing a claim with the carrier on your behalf. This does not apply to UPS Ground Saver or Economy shipments (see below).

If your package arrives damaged, please do the following:

1. Refuse delivery if the package is visibly damaged at the time of arrival, and note the damage with the driver.
2. If the damage is discovered after delivery, photograph the outer packaging BEFORE opening the box, then photograph the contents showing the damage.
3. Keep all original packaging, including boxes, packing materials, and labels. Carriers may require an inspection before approving a claim.
4. Notify us within 48 hours of delivery by submitting a damaged shipment report at help.allprotruckparts.com/damaged-shipment.

Once a claim has been filed, resolution is determined by the carrier. Refunds and replacements for damaged shipments will only be issued after the carrier approves the claim. Failure to report damage within 48 hours, discarding the original packaging, or opening a visibly damaged package without photographing it first may result in the carrier denying the claim, in which case we are unable to refund or replace the item.

Shipping Services

• UPS Shipping Services
• UPS Ground
• UPS 2nd Day Air A.M. (commercial addresses only)
• UPS 2nd Day Air
• UPS 3 Day Select
• UPS Next Day Air Saver
• UPS Next Day Air
• UPS Next Day Air Early

UPS Ground Saver and Economy Shipping
UPS Ground Saver and Economy are our lowest-cost shipping options, but they don't include claim support. If a package sent with one of these services is lost or arrives damaged, we can't file a claim or help resolve it. Choose UPS Ground or faster if you want that protection.

Returns
All Pro Truck Parts offers lifetime returns for any reason on NEW, UNOPENED items in the original packaging, with exceptions (see restocking fee, excluded categories, used items, sale items and special order items below).
To be eligible for a return, your item must be unused and in the same condition that you received it. It must also be in the original packaging.

Restocking fee and return shipping
Returns of new, unopened items are subject to a 20% restocking fee, which is deducted from your refund. You pay the shipping to send the item back, and shipping costs are not refunded.

Excluded categories
Engines cannot be returned. If one is defective, see defective parts (warranty) below.

Used items (if applicable)
Items marked as USED at the time of sale will be accepted for return up to 30 days from the date of sale.

Defective parts (warranty)
A part that fails is handled through the manufacturer's warranty process, not as a return. The manufacturer reviews the claim and decides whether the part is defective for the application it was purchased for. If you need a part right away, you will need to purchase a replacement rather than wait on the warranty review. Start a warranty claim at help.allprotruckparts.com.

Sale items (if applicable)
Only regular priced items may be refunded. Sale items cannot be refunded.

Special order items (if applicable)
Special order items may be eligible for a refund. The decision to accept a special order item for refund is left solely to the All Pro Truck Parts management team.

How to start a return
Start your return online at help.allprotruckparts.com/returns with your email or phone number and order number. Questions? Text us at (903) 527-5854 or email sales@allprotruckparts.com.
Ship your return to: All Pro Truck Parts, 3948 Interstate 30 W, Caddo Mills TX 75135, United States.
You are responsible for paying the shipping costs to return your item. Shipping costs are non-refundable. If you are shipping an item over $75, we advise using a trackable shipping service or purchasing shipping insurance. We don’t guarantee that we will receive your returned item.

Refunds
Once your returned item is received and inspected, we will send you an email to let you know we received it and whether your refund is approved.
If approved, your refund will be processed and credited to your credit card or original method of payment within 7 business days. For orders paid on our card terminal, text or email us to start the refund.

"Free Shipping" orders
If we paid the shipping on your order ("Free Shipping"), the cost of shipping it to you will be deducted from your refund when the item is returned and inspected.

Exchanges
We only replace items if they are defective or damaged. If you need to exchange it for the same item, start it at help.allprotruckparts.com/returns or text or email us, and send your item to the return address above.

Read our full return policy.