Motive Gear F7.5-373 ring and pinion paired with the R7.5FRMK Koyo master install kit, so a Ford 7.5 regear goes in with all new bearings.
If your Ranger, V6 or four-cylinder Mustang, Explorer, Bronco II or Aerostar is whining between 40 and 60 mph, or it went soft off the line after bigger tires, this is the one-box answer for the Ford 7.5 rear axle. You get a Motive Gear F7.5-373 ring and pinion in a 3.73 ratio together with the Motive R7.5FRMK master install kit, so the new gears go in on new Koyo bearings instead of the tired ones that started the noise.
The 7.5 is a 10-bolt-cover, C-clip axle with a 7.5 in. ring gear, a 28-spline pinion with a 1.626 in. stem, and a crush sleeve that holds pinion bearing preload. The pinion drives the ring gear, and the ratio between them decides how hard the axle multiplies engine torque. Many of these axles left the factory with 2.73, 3.08 or 3.45 gears. Moving to 3.73 turns the driveshaft faster for every turn of the wheels, which brings back launch and passing power when taller tires have effectively made the gearing longer, and helps a small V6 or four-cylinder pull a light trailer without hunting for a downshift.
First prove it really is a 7.5 and not an 8.8: both use a 10-bolt cover, so measure the cover or the ring gear. Our Ford 7.5 problems and rebuild guide shows the quick way to tell them apart and how to read the axle code on the door tag. Then separate gear noise from bearing noise and from an axle bearing, which growls with road speed rather than throttle. The whine on acceleration vs deceleration guide walks through it. If the teeth look clean and you are keeping the stock ratio, a bearing kit alone such as the Yukon YK F7.5 overhaul kit may be all you need.
This package is built for the Ford 7.5 in. rear axle used under the 1979-2010 Mustang (four-cylinder and V6; the V8 cars mostly got the 8.8), 1991-1997 Explorer, 1984-1990 Bronco II, 1990-1997 Aerostar, many Rangers, and a long list of Ford and Mercury cars from the same era. Ford mixed 7.5 and 8.8 axles inside the same model lines, so match the ring gear size and the 28-spline pinion to this listing, or send us your year and VIN and we will check the axle code. One important detail: when you go from a 2.73 or 3.08 to 3.73, the thicker pinion head can contact the standard differential cross pin, so a notched 7.5 cross pin (Motive 80-0271-1 or equivalent) is required and is not included. Notched pins are not meant for drop-in lockers. Browse more 7.5 and 8.8 parts in our hard parts section.
The master kit covers carrier and pinion bearings and races, pinion seal, crush sleeve, pinion nut, shims, ring gear bolts and the cover gasket. Set pinion depth with the shims first, then crush the sleeve a little at a time until preload reaches spec; Ford lists 14-19 in-lb for new bearings. Shim the carrier for .011-.016 in. backlash, torque ring gear bolts and bearing caps to 70-85 ft-lb, and check the pattern on both drive and coast sides. Our backlash and pinion depth setup guide explains reading the pattern. If you would rather never chase a crush sleeve again, the Ford 7.5 and 8.8 crush sleeve eliminator uses solid shims instead, and a pinion depth gauge like the Proform 66516 takes the guesswork out of the first step. Fill with about 5 pints of hypoid gear oil (Ford lists 75W-80 or 80W-90), plus friction modifier if you have a Traction-Lok. Drive gently for the first few hundred miles with no towing and change the oil after break-in, as covered in our ring and pinion break-in procedure.
| Axle | Ford 7.5 in. rear, 10-bolt cover |
| Ratio | 3.73 |
| Gear set | Motive Gear F7.5-373, 8620 steel |
| Install kit | Motive Gear R7.5FRMK, Koyo bearings |
| Pinion | 1.626 in. head, 28 spline |
| Fits | 1979-2010 Mustang, 1991-1997 Explorer, 1984-1990 Bronco II, 1990-1997 Aerostar and other Ford 7.5 axles |
| Note | Requires notched cross pin 80-0271-1 (not included) |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. The 7.5 and 8.8 both use a 10-bolt cover, but the ring gear, pinion and bearings are different sizes. Measure the ring gear or read the axle code; this package is only for the 7.5 in. axle.
Yes, if you are coming from a 2.73 or 3.08. The deeper 3.73 pinion head can hit the standard cross pin, so you need a notched Ford 7.5 cross pin such as Motive 80-0271-1. It is not included in this kit.
The R7.5FRMK kit includes carrier and pinion bearings and races, pinion seal, crush sleeve, pinion nut, setup shims, ring gear bolts and the cover gasket. It does not include axle bearings or axle seals.
Yes. The 3.73 ring gear bolts to the factory 7.5 carrier, open or Traction-Lok. Add friction modifier to the gear oil if you run the limited slip, and consider fresh clutches while the carrier is out.
It can be, but setting pinion depth, preload and backlash takes a dial indicator, an inch-pound torque wrench, a bearing press or puller and patience. Most people with no setup experience have a driveline shop install the gears.
Ford calls for hypoid gear oil in the 75W-80 to 80W-90 range, roughly 5 pints for a dry axle. Many builders use a quality 75W-90 GL-5 and change it after the first 500 miles of break-in.
