What You're Looking At
This is a 12-rib poly-v serpentine belt sized for the MP8 engine accessory drive. Volvo and Mack share this engine platform, so you'll see the same belt spec'd under both nameplates — that's why Volvo VNLs and Mack trucks with the MP8 both call for 12PK1625.
It's not a v-belt, it's not a 6 or 8 rib — count your ribs before you order. If the old belt shredded and you're guessing off memory, don't. Pull the tensioner off and count grooves, or read the belt if there's enough of it left to see numbers stamped on the backside.
Why These Numbers Cross
Volvo's own part numbers (20582557, 23961868) and the Mack numbers (S-21819, S21819) point to the identical belt spec — same length, same rib count, same profile. Gates K120640 and the Automann numbers are aftermarket versions built to that same 12PK1625 dimension.
Where guys get tripped up is length. A belt that's off by even 20-30mm won't seat right on the tensioner arm — you'll either not have enough tensioner travel left, or the belt will be too loose and start slipping and squealing inside a few thousand miles. There's no 'close enough' with these.
Pulley diameter and tensioner arm reach on the MP8 are consistent enough that these cross-references hold up in practice, but factory running changes happen. Confirm against the number stamped on your old belt or your VIN before you hit order.
Ordering From PartStop
We keep 12PK1625 on the shelf here in Tacoma — if you're local and your rig is down, call ahead and we'll have it at the counter same day. Ship nationwide too if you're not near us, and most orders go out same or next business day.
Comes with our standard 6+ month warranty. If it's wrong length or doesn't seat right on your tensioner, we'll sort it — just don't wait until you've run it 10,000 miles to check that box.
12PK1625 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 12PK1625. 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 |
|---|---|
| Gates | K120640 |
| FleetRun | FR-ENGN819 |
| Automann | 815.17625, 815.4120640 |
| Volvo | 23961839, 20582565 |
Frequently asked questions
Does 12PK1625 fit my 2012 Volvo VNL with a D13?
No — this belt is spec'd for the MP8, not the D13. Different engine, different pulley layout, different belt length. Check your old belt number or give us your VIN and we'll pull the right one.
Is this the same belt as Gates K120640?
Same spec, same 12-rib 1625mm length — Gates just runs their own part numbering. Functionally it's built to the same dimension as 12PK1625, but always confirm against your old belt's number since running changes do happen.
My old belt is Mack S-21819 — will 12PK1625 work?
Should — S-21819 crosses to the same 12PK1625 spec. But pull the old belt and check for any additional letters or suffix stamped after S-21819, and match rib count before you order, just to be safe.
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.