- Joined
- Nov 30, 2020
- Messages
- 382
- Reaction score
- 672
- Location
- MA, USA
- Vehicle Year
- 1989
- Make / Model
- Ford Bronco II
- Engine Type
- 4.0 V6
- Transmission
- Manual
- 2WD / 4WD
- 4WD
- Total Lift
- 5"
- Tire Size
- 31
- My credo
- Giving my truck more money than it deserves.
Hello all. Before I bought my locker, I had heard many people complain about them but not provide a satisfactory explanation why. I figured I should type up a short summary of my feelings about these traction devices to help you better decide if it's right for you.
I have a OHV 4.0L and M5 swapped Bronco II. In the back I installed an 31 spline 8.8 with 31s and 4.10 regear. When I did this I installed a Lock-Rite brand differential locker. That was nearly a year ago and over 15,000 miles. This is my daily driver after all
To start; traction is GOOD. Under power the car has a true locked differential. I would argue closing the differential is the second largest traction upgrade you can make after better tires. This type of locker should be durable in RBV applications with less than a v8. I have seen lots of complaints of these breaking, but I feel like if they couldn't stand up to the platform, I would have broken it. I pulled off the differential cover to change fluids recently and the locker isn't showing any wear or damage. Winter driving is much easier and didn't exhibit any of the scary handling characteristics others have reported. It gets much more rowdy when you are doing stunt driving, but is perfectly controllable with normal driving.
Unfortunately, there are a lot of bad things I have to say. This type of locker does not play well with manual transmissions. The nature of how they lock greatly increased drivetrain slack. Clutching too quick can cause the car to lurch forward. Idling along in traffic can hit a resonance where the car can buck forward and back. When I turn sharply, I have to be clutched in or inputting enough throttle to lock the differential completely. Intermediate throttle causes the differential to lock and unlock presumably as the driveshaft is tossed around. (This is embarrassing in the grocery store parking lot!) The car is true one-wheel-drive until its true two-wheel-drive. When you tip into the throttle, the car will pull to one side until the other catches up and locks. This makes highway lane keeping harder, but may affect the Ranger and Explorer wheelbase less. Sometimes on a flat road the differential will attempt to lock on the "tips" teeth. When the locker teeth slip into mesh, it emits a scary popping noise like you just broke a clip or an axle. I pulled over the first time this happened.
The locking action is abusive on the drivetrain and suspension. Offroad, the drivetrain can "wind up" and spring a wheel forward enough to unlock it. Since throttle position remains the same, the whole momentum from piston to other wheel kick the no-longer slipping wheel right back to speed. I have had to retorque my axle u-bolts several times. My transmission mount rubber completely separated from the metal below. The worst damage is taken in the transmission. All thrust surfaces are hammered with each lock and unlock. The junkyard transmission bearings all could do with replacing now. The most vulnerable part of an M5 transmission is the thrust bushings on the reverse auxiliary shaft. I had to reverse out of where I got stuck a few times and the drivetrain shock cracked the thrust bushings. These are no longer available from Ford and don't seem to be reproduced aftermarket. The only place I have been able to source them is a small few NOS listings on eBay and other used transmissions. (for reference they're E8TZ-7N037-A and E8TZ-7N037-C)
Second rebuild update; all the bearing bores are worn out. The most damage comes from the input shaft bearing and the tail housing output shaft bearing. The aluminum center carrier bowed out from shock and seems to have taken preload out of the bearings. I found a steel carrier (97 3.0 4x4 I think) and this will hold me over until I source a new 4.0 case and LSD.
TL DR: Auto differential lockers are the best value-to-traction you can buy. They are not for daily driving or use with manual transmissions.
I have a OHV 4.0L and M5 swapped Bronco II. In the back I installed an 31 spline 8.8 with 31s and 4.10 regear. When I did this I installed a Lock-Rite brand differential locker. That was nearly a year ago and over 15,000 miles. This is my daily driver after all
To start; traction is GOOD. Under power the car has a true locked differential. I would argue closing the differential is the second largest traction upgrade you can make after better tires. This type of locker should be durable in RBV applications with less than a v8. I have seen lots of complaints of these breaking, but I feel like if they couldn't stand up to the platform, I would have broken it. I pulled off the differential cover to change fluids recently and the locker isn't showing any wear or damage. Winter driving is much easier and didn't exhibit any of the scary handling characteristics others have reported. It gets much more rowdy when you are doing stunt driving, but is perfectly controllable with normal driving.
Unfortunately, there are a lot of bad things I have to say. This type of locker does not play well with manual transmissions. The nature of how they lock greatly increased drivetrain slack. Clutching too quick can cause the car to lurch forward. Idling along in traffic can hit a resonance where the car can buck forward and back. When I turn sharply, I have to be clutched in or inputting enough throttle to lock the differential completely. Intermediate throttle causes the differential to lock and unlock presumably as the driveshaft is tossed around. (This is embarrassing in the grocery store parking lot!) The car is true one-wheel-drive until its true two-wheel-drive. When you tip into the throttle, the car will pull to one side until the other catches up and locks. This makes highway lane keeping harder, but may affect the Ranger and Explorer wheelbase less. Sometimes on a flat road the differential will attempt to lock on the "tips" teeth. When the locker teeth slip into mesh, it emits a scary popping noise like you just broke a clip or an axle. I pulled over the first time this happened.
The locking action is abusive on the drivetrain and suspension. Offroad, the drivetrain can "wind up" and spring a wheel forward enough to unlock it. Since throttle position remains the same, the whole momentum from piston to other wheel kick the no-longer slipping wheel right back to speed. I have had to retorque my axle u-bolts several times. My transmission mount rubber completely separated from the metal below. The worst damage is taken in the transmission. All thrust surfaces are hammered with each lock and unlock. The junkyard transmission bearings all could do with replacing now. The most vulnerable part of an M5 transmission is the thrust bushings on the reverse auxiliary shaft. I had to reverse out of where I got stuck a few times and the drivetrain shock cracked the thrust bushings. These are no longer available from Ford and don't seem to be reproduced aftermarket. The only place I have been able to source them is a small few NOS listings on eBay and other used transmissions. (for reference they're E8TZ-7N037-A and E8TZ-7N037-C)
Second rebuild update; all the bearing bores are worn out. The most damage comes from the input shaft bearing and the tail housing output shaft bearing. The aluminum center carrier bowed out from shock and seems to have taken preload out of the bearings. I found a steel carrier (97 3.0 4x4 I think) and this will hold me over until I source a new 4.0 case and LSD.
TL DR: Auto differential lockers are the best value-to-traction you can buy. They are not for daily driving or use with manual transmissions.
Last edited: