What This Tensioner Is and Where It Lives
This is the spring-loaded arm and pulley assembly that keeps constant tension on the serpentine belt driving your alternator, A/C compressor, and water pump on Detroit's DD13 and DD15. It's bolted to the front of the block, and it's got a damper built into the pivot to keep the belt from jumping around when the engine load changes.
When these wear out you get belt squeal, belt slap under acceleration, or a belt that flat throws itself off the pulleys. Sometimes it's just the bearing in the pulley going bad, other times the whole spring/damper unit is shot and it won't hold tension anymore.
This one's used across a chunk of Freightliner Cascadia and Western Star trucks running the DD13/DD15, but Detroit's put a few running changes through over the years, so don't assume every DD13 in the yard takes the same part.
Why All These Numbers Cross
01-27425-000 (sometimes stamped as 0127425000 with no dashes) is the Detroit Diesel number, and it's the same physical part as Automann's FRT 127425000, Dayco 89105, Goodyear 49514, and Kit Masters N20 689419. These aren't knockoffs of each other — they're the same tensioner assembly sold under different labels because Detroit doesn't cast every one of these in-house.
The arm length, pivot bolt pattern, and pulley diameter all have to match or the belt won't sit right and you'll be back under the hood in a week. Aftermarket tensioners in this cross usually reuse the stock mounting so bolt pattern isn't normally the issue — it's more about which revision of the damper spring your engine actually needs.
Surest way to confirm: pull the old tensioner and read the number off the housing or the sticker on the pulley. If it says 127425000, 38501, or 23520317/23527565, you're in the right family. Don't go off engine serial number alone — DD13/DD15 production ran long enough that tensioner specs shifted.
Ordering From PartStop
We're in Tacoma and keep this one in stock because DD13/DD15 tensioners are a top failure item on trucks running 300k+ miles. Local shops and owner-operators can usually get same-day pickup if you call ahead.
Ship nationwide too, standard ground or expedited if your truck's down and you need it there tomorrow.
Every tensioner we sell carries our 6+ month warranty. If it's not right for your application, call us before you install it — that's cheaper than pulling it back off.
01-27425-000 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 01-27425-000. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| OE/Cross-Ref | 127425000, 38501, 23520317, 23527565, GT-38501, 89419, 38501HD, 814.89419, S-25351, F01772 |
| Automann | FRT 127425000 |
| Detroit Diesel (OEM) | DDE 2 |
| Dayco | 89105 |
| Goodyear | 49514 |
| Kit Masters | N20 689419 |
Frequently asked questions
Does 01-27425-000 fit my 2016 Cascadia with a DD15?
Probably, but pull the old tensioner and check the number stamped on the housing before you order. DD15 production ran through a few tensioner revisions and the arm/damper spec isn't always the same year to year.
Is this the same as the Dayco 89105?
Yes, Dayco 89105 crosses to this same tensioner assembly. Different label, same physical part — arm, pulley, and damper spec all match.
My tensioner pulley bearing is loose but the arm still holds tension — do I need the whole assembly?
Usually yes. These aren't sold as separate pulley/bearing kits in most cases, and once the bearing's got play in it the whole unit's on its way out anyway. Cheaper to replace the assembly once than to do it twice.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.