The best trailer lift axle conversion kit depends on your axle type, tube diameter, spring width, and desired lift. For a 3,500-pound axle with a 2-3/8-inch tube, the SPARKWHIZ and Dexter over/under kits are the closest matches. For a compatible #10 Torflex axle, consider the RecPro kit; Dexter also offers a Torflex lift kit, though the supplied product details do not specify its fitment range.
| Product | Best suited for | Key detail |
|---|---|---|
| SPARKWHIZ K7138400 | 3,500-lb leaf-spring axles | Advertised 4–5-inch lift |
| Dexter K71-384-00 | Matching 3,500-lb axles | Advertised 3–4-inch lift |
| Dexter K7138400 Conversion Kit | Buyers checking component listings | Lists spring seats, nuts, and U-bolts |
| RecPro Torflex Lift Kit | Compatible #10 Torflex axles | For 2,300–4,000-lb capacity |
| Dexter Torflex Lift Kit | Torflex or spring-hanger research | Listing details need confirmation |
SPARKWHIZ K7138400 Over/Under Kit
This kit is best for owners of a 3,500-pound axle with a 2-3/8-inch tube and 1-3/4-inch-wide leaf springs who want additional ground clearance. The listed lift is 4–5 inches, making it a higher-lift option than the Dexter K71-384-00 listing.
The package includes four U-bolts, two tie plates, two spring seats, four spacers, and eight nuts. Those listed components make it a complete conversion package for its specified axle and spring dimensions.
- Choose this if: Your axle and leaf-spring measurements match and you want the stated 4–5-inch lift.
- Check first: The fitment information is specific; it is not described as a universal kit.
Dexter K71-384-00 Conversion Kit
This Dexter kit is best for a 3,500-pound trailer axle with a 2-3/8-inch tube and 1-3/4-inch leaf springs. Its listed lift is 3–4 inches, so it may suit buyers seeking a more moderate lift than the SPARKWHIZ kit advertises.
The over/under design changes the relative position of the leaf springs and axle. Confirm the axle dimensions and suspension arrangement before ordering; the listed fitment does not establish compatibility with other axle sizes or suspension types.
- Better for: Buyers whose axle matches Dexter’s stated size and who want a 3–4-inch lift.
- Limitation: The listed lift is lower than the SPARKWHIZ kit’s advertised range.
Dexter K7138400 Component Kit
This listing is best for shoppers comparing Dexter K7138400 components or verifying a part number against an existing conversion-kit requirement. The supplied details identify two spring seats, eight nuts, and four U-bolts.
Unlike the other Dexter listing, the provided feature information does not state axle capacity, tube diameter, spring width, or lift amount. Compare its part number and included hardware with the exact installation requirements before treating it as a complete match.
- Choose this if: The listed components and part number match what your trailer or repair plan requires.
- Check first: The supplied details do not confirm fitment or a specific lift height.
RecPro #10 Torflex Lift Kit
This kit is best for owners with a compatible #10 Torflex axle rated between 2,300 and 4,000 pounds. It is a different style of lift solution from the over/under kits for leaf-spring axles, so buyers should identify the axle type before comparing products.
RecPro lists a 3-inch RV axle lift and says the package includes two #10 frame spacers, eight washers, eight locking hex nuts, and eight hex screws. The listing also describes the included hardware as intended for installation.
- Choose this if: Your axle is a #10 Torflex within the stated capacity range and you want a 3-inch lift.
- Avoid this if: Your trailer has a conventional leaf-spring axle rather than the specified Torflex setup.
Dexter Torflex Lift Kit
This Dexter product is best treated as an option to investigate for a Torflex-related trailer suspension project. However, the supplied features describe a single-axle hanger kit for double-eye springs, with a bushing, and say it contains components to attach trailer springs to the frame.
Those details do not state a Torflex model, axle capacity, or lift height. That makes it important to verify the part’s intended application directly against the trailer’s axle and suspension before buying.
- Consider it if: The product’s exact application matches your suspension and you need the listed hanger components.
- Limitation: The provided information does not establish that it raises a Torflex axle.
Buying Guide: How To Choose A Trailer Lift Kit
Does your trailer use leaf springs or a Torflex axle?
Start by identifying the suspension. An over/under conversion kit is intended for a leaf-spring axle arrangement. A Torflex lift kit is a separate category and must match the Torflex axle application. These designs are not interchangeable simply because both can be associated with raising a trailer.
Which axle measurements matter?
For the two specified over/under kits, check for a 3,500-pound axle, a 2-3/8-inch tube, and 1-3/4-inch-wide leaf springs. For the RecPro option, confirm that the axle is a #10 Torflex unit rated from 2,300 to 4,000 pounds. Do not rely on appearance alone; use axle and suspension information to verify the match.
How much lift do you need?
Compare the listed lift ranges with the clearance or towing-height change you need. SPARKWHIZ lists 4–5 inches, Dexter K71-384-00 lists 3–4 inches, and RecPro lists 3 inches. These figures are product claims, not a substitute for checking the installed geometry and trailer requirements.
What should you verify before installation?
Check the kit’s included hardware, axle configuration, and application details. If a listing omits key specifications—as with the Dexter Torflex listing here—confirm fitment before purchase. Suspension changes can affect trailer height and towing setup, so consult a qualified trailer service professional if the axle or installation requirements are unclear.
Frequently Asked Questions
What does an over/under axle conversion do?
It changes the axle’s position relative to the leaf springs to raise the trailer. The exact lift depends on the kit and installation configuration.
Can I use an over/under kit on a Torflex axle?
Do not assume so. Over/under kits listed here specify leaf-spring axles, while Torflex products use a different application. Match the kit to the suspension type.
How much lift do these kits provide?
The listed amounts range from 3 inches for the RecPro Torflex kit to 4–5 inches for the SPARKWHIZ over/under kit. Dexter K71-384-00 lists 3–4 inches.
Are these kits universal?
No universal fitment is stated. Each product has specific fitment details or, in some cases, incomplete specifications that require confirmation.
What is the first measurement to check?
Identify the axle and suspension type first, then verify capacity, axle-tube diameter, and leaf-spring width where applicable.