Erik's Toyota Differential info

Toyota Differential Info
Last update 09/18/06

What type of diffs does my Toy 4x4 have?
What is the gear ratio of my diff?
How wide are the various Toyota axles?

Front Diffs
Rear Diffs
Electric-Locking Diffs

Breif Toyota 4x4 history/definition of terms (for North America):

'79-85 pickups and 4Runners had front live-axle, leaf-spring suspensions.
'86-95 4Runners, '86-95.5 mini-trucks, and '93-'98 T100's have torsion bar Independent Front Suspensions (IFS).
'96-up 4Runners, '95.5-up Tacoma's, and 2000-up Tundra's and Sequoia's have coil-sprung IFS.
"First genereation" 4Runners are '84-89, 2nd gen are '90-95, 3rd gen are '96-03, and 4th gen are '03-up.
"Mini-trucks" are Toyota pickups prior to the '95.5 model year change to the "Tacoma."
The "mini-trucks" are also known as the "Hilux" in other parts of the world.

What type of differential does my Toyota 4x4 have? (top)

'79-85 Truck or 4runner: Front, Rear
'85-95 4cyl Truck or 4Runner (non-turbo): Front, Rear
'86-87 Turbo 4cyl Truck or 4Runner: Front, Rear
'88-95 V6 Truck or 4Runner: Front, Rear
'95.5-up Tacoma: Front, Rear
'96-up 4Runner: Front, Rear
Tacoma "TRD", Tacoma "PreRunner" 4x2, or
3rd gen. 4Runner w/ factory electric locking diff option: Front, Rear
'93-98 T100 (2wd and 4wd): Front, Rear
'00-up Tundra or Sequoia (2wd and 4wd): Front, Rear

What's my gear ratio? There are several ways figure it out: (top)

If you think your axle gearing has not been changed since it left the factory, you can read and decode the "axle code" from your vehicle information plate. Off-road.com has some pretty good information how to do this HERE (scroll down to the section titled "Gearing").
If your differential has been removed so that you can see and count the teeth on the gears, you can divide the number of teeth on the ring gear by the number of teeth on the pinion gear to come up with their ratio. For example, 41/10 gives you a 4.10:1 gear ratio (the most common stock ratio).
To verify gear ratios w/ the diffs on the vehicle, there is the "spin and count" method:
For "open" diffs:
- Block the tires at one end of the vehicle to keep it from rolling, and then jack up a tire on the other end.
- Place the transmission in neutral and release the parking brake if you are checking the rear diff.
- Spin the tire exactly TWO full revolutions while at the same time counting exactly how many revolutions the driveshaft spins (marking the driveshaft and tires beforehand will make it easier to count revolutions).
- The number of revolutions the driveshaft spins is your gear ratio.
  If it spins just over 4 times, then the ratio is probably 4.10; 4-1/3 = 4.30; 4-1/2 = 4.56; just under 5 = 4.88; 5-1/3 = 5.29, etc.
For limited slip (LSD or "posi"), locking differentials, spools, etc.:
- With these types of diffs, you won't be able to turn one tire w/o the tire on the opposite side of the axle turning with it.
- In this case, follow the directions above except raise both tires off the ground and turn them exactly ONE full revolution while counting driveshaft revolutions.
- Again, the number of driveshaft revolutions is your gear ratio as mentioned above.

Toyota Axle Widths: (top)
(all widths are measured wms-wms, wms=wheel mounting surface)

'79-85 front axle~ 55.5", rear axle~ 55"
'86-95 front IFS~ 59", rear axle~ 58.5"
Tacoma & '96-up 4runner front IFS~ ???, rear axle- 60"
T100 front IFS~ 65", rear axle~ 66.75"
Tundra front/rear~ ??
'90-97 Landcruiser FJ-80/FZJ-80 front axle~ 63.5"

* Another tidbit: 2wd 4runners, Tacoma "PreRunners," T100's, and Tundra's use 6-lug wheels- same as the 4x4's
(the other 2wd's use 5-lug)

Front Differentials (top)
The 4cyl 8" diff	'79-85 Trucks and 4Runners all have 4-cylinder engines and use what most call the 4cyl 8" diff in the front (the same one they use in the rear)- see "4cyl 8" diff" below.
The 7.5" IFS diff	'86-95 IFS trucks, 1st and 2nd gen 4Runners, and all '93-98 T100s use a 7.5" front diff that is offset to the passenger's side. Later models came with ADD (Automatic Differential Disconnect) which uses a vacuum actuated mechanism to disconnect the drivers side axle shaft from the differential. Carriers and gear sets are interchangeable between the two different versions (and also happen to be the same as used in the 2wd Toyota pickup 7.5" diffs). One difference between ADD and non-ADD diffs is that the carrier in an ADD differential has needle bearings supporting the axle shafts at the differential. The non-ADD diffs did not have this bearing and sometimes the passenger side axle flange wears the carrier and becomes loose or wobbly, eventually causing oil leaks, noise, and possible spider gear damage. ADD and non-ADD diffs are swappable as are most of their parts. This makes it possible to change your ADD diff to non-ADD by simply swapping parts as I've done in the picture to the right. This is desirable to some people since some of the ADD stubs are smaller diameter than the non-ADD stubs and are therefore slightly weaker.
Late-model 7.5" diff	Tacoma's, Tundra's, Sequoia's, and 3rd gen 4Runners have a high-pinion 7.5" IFS front diff offset to the drivers side. The high-pinion design is used so that the rack and pinion steering and anti-sway bar on these vehicles can run under the front driveshaft. The housing is a unique bolt-together design. The carrier inside is exactly the same as the '86-95 IFS diffs, so LSD's and lockers for it are also the same. However, since this is a high-pinion diff, the gears for it are different (reverse-cut) than the earlier diff. There is an ADD and non-ADD version of this diff as well. These diffs use different gear sets than the earlier IFS diff because of the high-pinion design. * I've heard that the latest model V8 4runners now have an 8" IFS diff. I have no info on this one yet.
8" IFS diff	The latest model 4runners, Tacomas, Tundras and probably Sequoias now use an 8" IFS diff with 30 spline axles, but I have no info on this one yet. It should look very similar to the one above.
The Hi-pinion 8" diff	‘90-97 Landcruisers (FJ-80 and FZJ-80) use a high pinion, reverse-cut front diff based on the V6/Turbo rear diff. The high pinion design allows the steering on these vehicles to run behind the axle and under the driveshaft. Carriers (i.e. lockers, LSD's) from the 8" V6/Turbo diffs can be installed (direct bolt-in) in the hi-pinion diff. The entire diff is also a direct bolt-in to all front and rear axles that use an 8" diff. This diff is desirable to some straight-axle mini-truck and 4runner owners for a couple of reasons. First, the reverse-cut design of the gears is stronger than simply using a rear diff and gears up front as the factory did since its not using the weaker "coast" side of the gears when driving forward. For this reason, this diff is generally only used in the front axle. Second, the hi-pinion design gives very good ground clearance for the pinion and driveshaft as well as improves driveshaft operating angles. In North America, almost all of these diffs came from the factory with 4.10 gears. Aftermarket gears for this diff are more expensive than most since they are either imported or custom made in limited quantities. At this time 4.88 and 5.29 are the only aftermarket ratios available.

Rear Differentials (top)
	Diff Housing (3rd member) Identification 4cyl has 3 ribs on each side. V6/Turbo has 4 ribs on each side and the trapezoid shaped top rib. Note- Starting in about '96, the V6 diffs started using a casting that looks nearly the same as the T100/Tundra casting from the outside. However, it doesn't have the trussed bearing cap on the inside, and the outside uses the smaller 8mm mounting studs.
	Axle Housing Identification 4cyl/V6/E-locker has a dome-shaped cover. T100/Tundra has deeper, blocky cover to accomodate the bearing truss.
The 4cyl 8" diff	All pre-'95 4-cylinder 4wd mini-trucks & 4Runners use the Toyota 8" 2-pinion differential front and rear (except turbo models). This is known as the "4cyl diff." This diff is by far the most common diff in older Toyotas. Ten 10mm ring gear bolts, 27 spline pinion shaft.
The V6/Turbo 8" diff	4cyl Turbo and V6* 4Runners and mini-trucks use the Toyota 8" 4-pinion differential in the rear. This diff is known as the "V6/Turbo diff." It has larger carrier bearings, is generally stronger than the standard 4cyl version, and is a direct swap into axles that use the 4cyl 8" diff. Separate gear sets are made for the V6 style diff (only from Toyota and Precision Gear), but cheaper, more readily available 4cyl style gears are commonly made to fit- the only difference being a very slightly larger pinion gear on the V6 style gear (the actual strength difference in gear sets is debatable). The strength increase in this diff over the 4cyl diff comes mainly from the beefed up housing, which stiffens the entire assembly, keeping the gears in proper (stronger) alignment. Although somewhat rare, there is a version of this diff that came from the factory with 4.88 gears. The carrier (3rd member housing) has a different pinion offset so that the ring gear doesn't need to be as thick. This means that no gears other than the factory 4.88's will fit this particular diff. However, diff cases, commonly called carriers (factory, LSD, lockers, etc.), for the standard V6/Turbo diff should be interchangeable (4cyl and V6/Turbo carriers are NOT interchangeable). * A few V6 trucks and 4runners have been found to have come with the 4cyl style diff from the factory. Nobody knows why. Ten 10mm ring gear bolts, 27 spline pinion shaft.
The T100/Tundra diff	All 2wd and 4wd T100's, Tundra's, and Sequoia's use a newer/stronger 8" 2-pinion diff. Tacoma 4x4's and Tacoma PreRunner's that don't come with the electric locker, as well as V6 Tacoma 4x2's also came with this diff. One easy way to identify it is by the larger mounting hardware (10mm studs w/ 14mm nuts) vs. the smaller stuff on the older diffs (8mm w/ 12mm nuts). It also has a different shaped diff cover. and a slightly larger diameter bolt pattern and flange (about 1/4" larger) than the 8" 4cyl or V6 diffs. It has a large one-piece carrier bearing cap (or "truss") that bridges over the ring gear to add strength. The axles that fit into these diffs are the same size as the earlier 8" diffs (30 spline). In the past this diff has also been mistakenly called an 8.4" or 8.25" diff. The ring gear actually measures 8", but it is not compatible with the older 8" diffs at all. The extra strength of this diff comes from the bearing cap/truss and large diameter pinion gear shaft. Aftermarket parts have so far been fairly limited for this diff. At this time, the only LSD available is the TRD/Kazuma clutch-type 3-pinion LSD, the OEM 4-pinion Tundra TRD LSD, and the only lockers available are the Powertrax "Lock-right," "No-Slip," and the ARB Air Locker (RD-89). Update- Tractech also now makes a Detroit Softlocker and Truetrac for this diff. This diff cannot be fitted to an older style 8" axle because it uses a larger diameter mounting bolt pattern and because more space inside the housing necessary to accommodate the large bearing cap. The different bolt pattern also makes it very impractical to swap in an electric locking Toyota diff (the whole mounting flange would have to be re-done using a special jig). Twelve 12mm ring gear bolts, 30 spline pinion shaft. * 4Runners do NOT use this diff at all. Late-model 4Runners still use the V6 8" diff above.

Toyota Electric-Locking Differentials (top)
Electric Locker	A factory option on 3rd Gen. 4Runners, Tacoma 4x4's, and Tacoma PreRunner 4x2's is an electric locking rear differential. This diff is a 4-pinon design based on the Turbo/V6 8" diff and uses the same gear sets. These locking diffs can be retrofitted into 8" diff axles if the axle housing is modified (see this article for more info). It cannot be easily retrofitted into a T100/Tundra or open-diff Tacoma style axle housing because the mounting bolt pattern is smaller. It "could" be done by an axle builder by doing major work to the mounting flange, but that is not really a practical option.
Hi-pinion Electric Locker	A factory option on ‘93-97 Landcruiser FZJ-80's is a hi-pinion electric locking front differential. It can be installed into modified 8" axle housings, similar to the 4Runner/Tacoma locker mentioned above. The reverse-cut gear sets for this diff are the same as for the standard hi-pinion diff mentioned earlier. These vehicles also had an optional rear 8.875" electric locker . This one has been retrofitted into other Landcruiser models with considerable effort (see this article), but it doesn't appear to be compatible with any non-Landcruiser vehicles.

Electric Locker Info
Toyota Electric Locker Links: -4x4wire's electric locker installation article -Mike Carter's E-locker install -Ken Emanuel's E-locker install -Ed & Judy's E-locker install -Carl Whitmore's CJ2a w/ dual hi-pinion electric lockers -Landcruiser FJ80 rear locker into FJ55 front Tacoma/4runner- "The Grey Wire Mod" to allow the factory locker to be engaged w/o being in 4-low - 4x4wire - CustomTacos.com - Offroaders.com InchwormGear.com is a great vendor who has a lot of E-locker parts and experience.	Toyota Electric Locker E-mail Threads: (lots of good info in these old emails) -Karl Bellve and myself -Scott Muir and myself -Carl Whitmore (taken from the Toy4x4 list)
Home-fabbed wiring to control a Toyota Electric Locker using relays: (click to enlarge) Designed by Scott Muir, drawn by Karl Bellve and I
Special Thanks to Karl Bellve and Scott Muir for all the help with the electric locker info!

I would also like to thank Sean (aka "GearMan") at River City Differentials. He has been very helpful and doesn't seem to mind answering my many questions. He and his shop are highly recommended by members of the Toy4x4 mailing list Pirate4x4.com BBS, and others. Let him know his info is being put to good use!
River City Differentials
Rancho Cordova, CA
(916) 852-7109

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