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  1. Trailer Leaf Spring Suspension
  2. Universal Group
  3. Camper
  4. Car Hauler
  5. Utility Trailer
  6. Leaf Springs
4-Leaf Slipper Spring w/ Flat End for 3,700-lb Trailer Axles - 30" Long

4-Leaf Slipper Spring w/ Flat End for 3,700-lb Trailer Axles - 30" Long

Item # SP-040275
Our Price: $63.28
Trailer Leaf Spring Suspension
This item qualifies for Free Shipping
Shipping Weight: 15 lbs
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Slipper leaf spring acts as part of a trailer's suspension system by providing an attachment point for a 3,700-lb axle. Spring flexes to resist shock and also ensures a smooth ride. Includes bushing with 9/16" inner diameter. Lowest Prices for the best trailer leaf spring suspension from Universal Group. 4-Leaf Slipper Spring w/ Flat End for 3,700-lb Trailer Axles - 30" Long part number SP-040275 can be ordered online at or call 1-800-496-5010 for expert service.
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Universal Group Trailer Leaf Spring Suspension - SP-040275

  • Camper
  • Car Hauler
  • Utility Trailer
  • Leaf Springs
  • Slipper Springs - 1-3/4 Inch
  • 30 Inch Long
  • 3700 lbs
  • Universal Group

Slipper leaf spring acts as part of a trailer's suspension system by providing an attachment point for a 3,700-lb axle. Spring flexes to resist shock and also ensures a smooth ride. Includes bushing with 9/16" inner diameter.


  • Leaf spring acts as part of your trailer's suspension system
    • Provides attachment point for your trailer's axle
  • Multiple leaves allow flexibility to absorb road shock
    • Allows for a smooth ride
    • Reduces wear and tear on trailer
    • Ensures level ride on bumpy and uneven surfaces
  • Sturdy steel construction
  • Nylon bushing included
  • Pre-mounted hangers or aftermarket hanger kit (sold separately) required for installation
    • Eye of spring attaches to hanger mounted on trailer frame
    • Slipper end slides into hanger or equalizer


  • Quantity: 1 leaf spring
  • Spring capacity: 1,850 lbs
  • Axle capacity: 3,700 lbs
  • Length from center of spring eye to end of spring (unloaded): 30"
  • Spring width: 1-3/4"
  • Eye diameter with bushing: 9/16"
    • Eye diameter without bushing: 7/8"
  • Leaf thickness: 3/8"
  • Number of leaves: 4
  • Additional dimensions: see table

Flat End Slipper Spring

Part NumberABCDE

Note: To ensure proper axle alignment and suspension performance, leaf springs should always be replaced in pairs.

Leaf springs are an integral part of your trailer suspension system. The leaf springs provide the attachment points for your trailer's axle, suspending it from the frame of your trailer. Each spring flexes to absorb road shock as you travel, allowing the axle to move somewhat independently of the rest of your trailer. This helps to reduce wear and tear on the trailer and also ensures a smooth ride.

Slipper leaf springs attach to hangers that are welded onto your trailer. The eye of this spring will attach to the front hanger with a suspension bolt. The flat slipper end of the spring will slide into the rear hanger. If you have a tandem- or triple-axle trailer, the slipper end will slide into the equalizer that connects multiple springs. The shape of the slipper end of a leaf spring may vary slightly due to differences among trailer manufacturers. Because of this, it's important to check your leaf spring's slipper end before purchasing a replacement spring.

To mount this spring, you will need hangers, a suspension bolt, and possibly a spring keeper bolt, depending on the design of the rear hanger. If you are simply replacing a spring, you may still have hangers welded onto your trailer, but it would be wise to replace the bolts as they can experience wear. It is also recommended that you replace the other leaf spring in your setup at the same time. Because springs can sag and elongate as they wear, this new spring may not exactly match the old one, and the alignment of your trailer could be affected.

If you are fabricating a trailer, you will need to purchase a hanger kit for installation. To determine the type of hanger kit that you need, you must know the specific type of leaf spring that you have, as well as your axle capacity. Depending on the hanger kits used with them, springs can be configured to work for single-, tandem- or triple-axle applications. Hangers and other suspension components can also be purchased separately if there isn't a complete kit that works for your setup.

UNA-040 Universal Group Slipper Trailer Leaf Spring - 4 Leaf - 1,850-lb Capacity

Replaces WIG4

Customer Satisfaction Score:

Customer Reviews

4-Leaf Slipper Spring w/ Flat End for 3,700-lb Trailer Axles - 30" Long - SP-040275

Average Customer Rating:  5.0 out of 5 stars   (112 Customer Reviews)

Slipper leaf spring acts as part of a trailer's suspension system by providing an attachment point for a 3,700-lb axle. Spring flexes to resist shock and also ensures a smooth ride. Includes bushing with 9/16" inner diameter.


I rebuilt an old boat trailer and made it a water wagon,
the springs are awesome. 300 gal is nothing for the springs.
Thank you


Super fast delivery. Exactly as expected and better priced. I will use etrailer again.


Very good product. My mechanic told me to go get the same thing I had on my trailer, only more leafs. Knowing very little about these, I couldn't find what I thought I needed...then etrailer came up on Google search. I got what I thought would be needed and all the mechanic had to get were ubolts etc to connect to axle.
These leaf springs should be strong enough to help me save fuel when hauling wood and mulch no matter what vehicle I am using.
Thanks for helping me get what I needed.


Easy to install springs.


The only minor issue was that the springs were sticking through the box. The springs went on quickly, and fit properly. My only wish is that the product be made in America. I would be glad to pay a bit more.


Got the springs yesterday 2/26 , put them on today 2/27. They fit and worked great.
Thank y’all Mark D.

I have been using this product in all types of terrain and it has been working perfectly I have no complaints whatsoever.
Mark - 02/28/2022


Very fast courteous service nice to do business with somebody like that




I have a 20+ year old flat bed trailer. One of the leaf springs [finally] broke. This replacement set was a drop in fit! Perfect for my flat bed trailer. Replacing the springs was made easier by having the right parts and etrailer had them. Thanks, etrailer! Great price, right fit and fast shipping. Can't ask for more.


I was searching for a replacement on an out dated boat trailer. The spring had two broken leaves. It was an unusual slipper spring that mounted crosswise. While I did not find one with the exact configuration, I was able to find a similar one with adequate load capacity and had the correct dimensions for proper mounting. It is working fine.


Lori was very helpful and delivery was quick.


I was restoring my boat trailer and ordered these springs along with hangers and etc. All items were excellent and price was the best I found. Etrailer shipped all my items together in one box which makes it cheaper for shipping. They box items up excellent and delivered by UPS


The springs work just fine. They are a little over kill for my boat. It has raised the trailer more than I would like.
That's my fault. They are exactly what I ordered. Also I like that you can grease them.


Good part came on time

George - 11/20/2021


I ordered a fender, springs,8 and misc parts for my magic tilt boat trailer to get it back in good condition. Everything was exactly what I ordered and worked great. The order was delivered in two days with free shipping The customer service was also very helpful (thanks Taylor ) Only place to go for your trailer needs.


Very helpful taking my order and great pricing . Also free shipping at $100.00 is a great money saver based on the weight of trailer leaf springs and all the hardware i received shipping would have been a killer . I will be using this place again for sure !!


Great looking quality, fast fast shipping ??, gives my trailer a higher tire clearance from the deck which is what I needed. My only recommendation to etrailer is seeing if their supplier can start making this same spring in a 32" version due to that's what this 30" spring is replacing. I made some modifications to make this spring work. Overall this is a nice spring pack assembly.


Needed new spring sets in a hurry for an older trailer which had broken springs. The etrailer organization provided the right parts at a good price, with quick shipping. Just what was needed.


Everything 100% correct anything I need to concern with a trailer will definitely be to you thank you very much


Replaced rusty springs thanks for the great product


I tried finding these springs on both [sites] with very little luck. I'm glad I googled it and found Etrailer. The seller on [site] wanted more for shipping then my whole order was combined at Etrailer plus I got my order in 3 days. Great price with great service. I will definitely come back.


Great customer service, good shipping and tracking information, and great follow up throughout the process. Etrailer is an easy company to work with that has great prices on good products. Highly recommended!


Quality parts for a great price. I now have a trailer with better suspension than when I bought it. I am confident it will carry the loads I haul in it for years to come.


The Springs that I ordered from etrailer were delivered promptly, packaged correctly, and were an exact fit. I will buy from etrailer again.


Product was exactly as described and arrived in a timely manner. Customer service was great too. Web page was easy to navigate and I would recommend etrailer to anyone looking for trailer parts. They have it all.

Show More Reviews

See what our Experts say about this Universal Group Trailer Leaf Spring Suspension

  • Looking for Spring for Model R1828 Yacht Club Boat Trailer With 1-3/4 x 30 Leaf Slipper Springs
    As long as a spring is of the correct weight rating, size and type (slipper or double-eye), the number of leaves in a spring isn't important. This is especially true since springs should always be replaced in pairs. If you are confident that your trailer has a 3500 lb axle, the # SP-040275 slipper spring should work just fine for you.
    view full answer...
  • 4-Leaf Slipper Spring Recommendation that is 1-3/4 inches Wide and 30 inches Long
    I believe the closest spring we carry to what you are looking for is the 4-Leaf Slipper Spring part # SP-040275. This is a 4-leaf spring that is 1-3/4 inches wide that is 30-1/4 inches long. This spring is designed for a 3.500 lb axle. If the axles you have on your trailer are 3,500 lb capacity this spring would work well for you. I attached an FAQ article on slipper springs for you to check out also.
    view full answer...
  • Replacement Leaf Springs for 1989 TeeNee Boat Trailer
    As leaf springs become worn, they tend to flatten out, which would explain the slightly longer dimensions of your existing slipper spring. The correct replacement spring you need will depend on the capacity of your axle. If your TeeNee boat trailer uses a 3500 lb axle, then the # SP-040275 is the correct replacement. For a 3000 lb axle, use # SP-040275. Leaf springs should be replaced in pairs.
    view full answer...
  • Thickness of the 4-Leaf Slipper Spring SP-040275
    I went and grabbed a 4-Leaf Slipper Spring # SP-040275 from our warehouse to measure it and found that it is 1-7/8 inches thick if you only look at the leafs. If you add in the bolt that runs down the center you would add 1/2 an inch to the overall thickness.
    view full answer...
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  • 4-Leaf Slipper Spring Recommendation for a 3,500 lb Axle Boat Trailer
    As long as the capacity of the spring matches what the trailer needs it won't matter at all if there are a different number of leaves on the spring. Based on the weight of your trailer and the fact the # SP-040275 matches up dimensionally this spring would be the perfect spring to use. I attached a review video for you to check out as well.
    view full answer...
  • How to Find Axle capacity of a Trailer to Choose the Right Replacement Slipper Springs
    The leaf springs on a trailer will need to meet or slightly exceed the axle capacity. So if you know the axle capacity then each spring should be rated for at least 1/2 of that capacity on a single axle trailer. The axle capacity may be listed somewhere on the trailer frame near the front of the trailer. Another option is to pull off a hub and retrieve the inner and outer bearing numbers stamped into the sides of the bearings. With that information I can determine the likely hubs that...
    view full answer...
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  • Can Bottom Leaf be Removed When Replacing 3-Leaf Slipper Spring with 4-Leaf Slipper Spring
    You can easily replace a 3-leaf slipper spring with a 4-leaf option like the Universal Group Slipper Spring # SP-040275 that you referenced. You should definitely not remove the bottom leaf from this as that would lower the weight capacity plus the center bolt that holds all of the leaf springs together would need to be modified. All the extra leaf spring will affect is the height of your trailer but that will be very minimal. Just be sure that the leaf spring is rated properly, has the...
    view full answer...
  • Replacement 32 Inch Leaf Springs for Trailer
    The closest leaf springs we have available to the specifications you mentioned is the Universal Group 4-Leaf Slipper Spring # SP-040275. These slipper springs have a 30 inch length from the center of the spring eye to the end of the spring. Leaf springs will stretch over time, so it's possible that the leaf springs on your trailer originally had a length closer to 30 inches. These are designed for axle capacities of 3,700 pounds and have a width of 1-3/4 inches. The eye diameter with...
    view full answer...
  • Trailer Leaf Slipper Spring Hardware
    The Trailer Leaf Slipper Spring, part number SP-040275, is not galvanized or coated it is a solid steel leaf spring. The leaf springs are shipped with a light coat of paint for rust protection but are not rust proof. Coating or treating the springs would not work because of the flexing and rubbing the springs are subject to under the trailer. The leaf springs can be painted but the paint will not last long with the constant flexing and road debris hitting them. The mounting hardware...
    view full answer...
  • Can 3700lb 4-Leaf Slipper Spring SP-040275 Be Used On Trailer W/ 3500lb Axle?
    Yes, the 4-Leaf Slipper Spring w/ Flat End for 3,700-lb Trailer Axles - 30" Long # SP-040275 would work on a 3500lb axle, they are just ever so slightly stiffer. Now to make sure they will fit your trailer you will need to measure from the center of the spring eye to the end of the spring of your current leaf springs, and the width of the spring. You will need to make sure the axle is off the ground with no weight on spring, as weight on the spring will cause it to stretch and give you...
    view full answer...
    Image 1 for
  • Availability of 1-3/4 inch Wide Slipper Spring for 3,500 lb Trailer Axle
    The closest slipper spring we offer to what you are looking for is a 4-Leaf spring part # SP-040275 which is 1-3/4 inches wide, for a 3,700 lb axle and is 30 inches long.
    view full answer...
  • How to Select the Correct Leaf Spring Size for a Tandem Axle Trailer with Slipper Springs
    To determine the correct slipper springs for your tandem axle trailer, the axle capacity will need to be determined. Selecting a spring by length alone could cause the selection to be under or over capacity substantially. If your spring is shaped like the 4-Leaf Slipper Spring for 4,100-lb Trailer Axles, # SP-264275, and each axle capacity is 4,100 lbs or just below that, then this spring should work for you. This is the only spring we have with the slipper end shaped this way. If your...
    view full answer...
    Image 1 for
  • 1-3/4 Inch Slipper Spring That is 30 Inches Long and Over 2,500 lb Capacity
    We have a couple of slipper springs that may work for you, as they are 1-3/4 inches wide, measure a total of 30 inches, and have the capacity you need. Springs do elongate over time, but you may have to have your brackets re-positioned if the 30 inch length isn't enough (this is the longest available for 1-3/4 inch or 2 inch springs). You will want to get a spring that is as close to your axle capacity as possible without going under it's capacity. - 2,900 lb Axle: 3-Leaf Slipper Spring...
    view full answer...
  • How To Find Correct Replacement Leaf Spring For Trailer With Single 3500lb Axle
    I would be happy to help you determine the correct replacement leaf springs for your 7'x14' cargo trailer with a single 3500lb Lippert axle but I will need to know if your leaf springs are a slipper spring, or double eye leaf spring and the length of the spring. For example the 3-Leaf Double-Eye Spring for 3,500-lb Trailer Axles # SP-216275 is a double eye leaf spring for a 3500lb axle that measures 23-1/8" from the center of the spring eye to center of the spring eye as shown in the included...
    view full answer...
    Image 1 for Image 2 for
  • What Size Bolt Is Needed for the 4-Leaf Slipper Spring 3,700 Lb with Flat End
    The 4-Leaf Slipper Spring w/ Flat End part # SP-040275 is designed for 9/16" bolts only, the Spring-Eye Bolt with Locknut for Slipper Springs part # 166079. There isn't any way to use a 3/4" bolt with this leaf spring nor do we have an option that will in this size.
    view full answer...
  • Replacement Slipper Springs to Replace 32 Inch Long Springs
    The 30 inch slipper springs we carry don't have a measured radius but the 28 inches you're looking for will work just fine. Your 32 inch springs were likely a little shorter than that originally and have flattened over time. Although probably not the full 2 inch difference but enough that our 30 inch springs will work on your trailer. We carry three different weight capacities that are 30 inches: 4-Leaf for 3,700 pound axles # SP-040275 3-Leaf for 2,900 pound axles # SP-039275 2-Leaf...
    view full answer...
  • 30 inch Long Slipper Spring Recommendation for Boat Trailer
    We have a few options for 30 inch long slipper spring that is 1-3/4 inches wide. For a 3,700 lb axle option we have the part # SP-040275. For a 2,900 lb axle option we have the part # SP-039275. For an 1,800 lb axle you would want the part # SP-038275.
    view full answer...
    Image 1 for
  • Replacement Slipper Style Leaf Spring for 1984 Tee Nee Trailer
    For your 1984 Tee Nee trailer, the number of leaf springs is not the determining factor but rather the length and the capacity rating. The 3-Leaf Slipper Spring w/ Flat End for 2,900-lb Trailer Axles - 30" Long # SP-039275 is a great replacement option based on your photo as long as your axle capacity is 2900 lbs because each spring is rated for 1450 lbs. If you have a 3,500 lb axle then instead you would want # SP-040275 because it is a higher weight rated spring. If the trailer axle...
    view full answer...
    Image 1 for
  • Recommended Spring Seat for a Square Axle Tube
    Correct, you will need to have a spring set installed on the axle tube to hold the leaf springs in place and prevent them from sliding back and forth. That said, although we do not have any spring seats specifically for a square tube axle you can use the Spring Seat part # TRSS300 by grinding the ends down and then welding it to the axle tube.
    view full answer...
  • Could Spring Eye-Bolt 166081 be Used with Leaf Spring SP-040275
    The spring eye-bolt part # 166081 is 1/2 inch shorter than the part # 166079 at 3 inches and would work well with the slipper spring part # SP-040275 that you referenced.
    view full answer...
  • Replacing Old Slipper Springs and U-Bolts
    Though the leaf springs are rusty, they do not seem to look pitted, so they should still be fine. It wouldn't hurt to clean them off with WD-40 or a rust remover to make sure they don't get worse. If you did want to replace them though, you could go with something like the Universal Group # SP-040275. As I couldn't tell 100% how wide the leaf spring is, this is a 1 3/4 wide one. It is also much longer with the overall length of 30 inches, so the rear hanger would most likely need to be...
    view full answer...
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  • Replacement Leaf Spring for 1987 Shoreline Boat Trailer 3000 lb
    The most important thing to match when replacing trailer leaf springs is the weight capacity. Which for a trailer that weighs 3,000 lbs I'd recommend going with 3,700 lb axle springs like # SP-040275 which are 30 inches long. This means you'll need to move out your old hangers wider which we have replacements with # 115706S.
    view full answer...
  • Replacement Leaf Springs and U-Bolts for a 1987 Shore Line Boat Trailer
    Thank you for submitting the photo of your setup. Considering the height of your axle and the amount of clearance you currently have from the axle to the frame of your trailer you wouldn't have enough room to put your axle above the leaf spring. You would barely have a couple of inches of suspension travel. For U-bolts you would want the part # SP01-160 and then for plates you would want the # 117594. Based on the dimensions of your current slipper springs the # SP-040275 that you referenced...
    view full answer...
    Image 1 for
  • Replacement Slipper Springs for a 2,100 lb Trailer
    The most important factor in picking out a new leaf spring for a trailer is to match the capacity needed. Going with a 3,500 lb spring for a 2,100 lb trailer is going to give you a very harsh ride. For a spring similar to the # WIG4 that is better rated for your trailer we have the # SP-039275 which is for a 3,000 lb axle or part # SP-038275 for a 2,000 lb axle. If you need all 2,100 lbs of your trailer's capacity you would have to go with the # SP-039275. If you have a 2 inch square...
    view full answer...

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Info for this part was:

Employee Michael H
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Employee Cole B
Installed by:
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Updated by:
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