View Full Version : What is it I've got? Rear Diff

mojave joe
12-06-2011, 01:41 PM
Hi, I'm hoping someone can enlighten me, I'm trying to determine what diff I have in my 95 Taco 4x4.
1. I was told by Marlin that I probably have a 8.4 diff.
2. I read on one forum, the ring actually measures 8", the .4 is something to do with the series or mat'l.
3. I see on one site listings for gears based on 4cyl or 6cyl-nothing about size
4. I see listings on one site for both 8 and 8.4
5. I only see empty housings for 8

The truck is the 2.7, I'm running 33" tires. The stock 4:10 gears are tolerable, but I have a FWC that I know is going to be a boat anchor when I get it on the truck. I do a lot of long distance commuting so I believe I want to go with 4:56 gearing, as not to sacrifice too much high speed.

...not to mention, what's in the front?

12-06-2011, 02:02 PM
Non TRD (rear e-locker equipped) Tacoma's do in fact have what is commonly referred to as a 8.4" diff. The 8.4" diff is entirely different from the common 4cyl/V6 8" gears and the two (8/8.4) have different axle housing mating. Finding a loaded 8.4" housing is going to be harder to source than the 8" varieties but gears, install kits, etc are all commonly available for the 8.4".

While its commonly referred to as the 8.4" it doesn't measure 8.4" but you'll need to be clear when sourcing your parts. Any Toyota familiar gear shop/vendor should have no problem getting you the parts needed.

The front in all 96-04 (TRD or non) Tacoma's is a reverse cut (high pinion) 7.5" diff. Again parts are widely available for all the common ratios (4.56, 4.88 & 5.29)

More info on diffs here:

Owyhee H
12-06-2011, 02:07 PM
You should have the 8.4 in the front and a 7.5 in the front. The 8.4 is very strong. The 7.5 is weaker but as long as your not putting too big of tires on you should be fine. The older toyota trucks and the TRD have the 8".

^^^Edit: He beat me to it.

12-06-2011, 02:12 PM
This should help you out: http://home.4x4wire.com/erik/diffs/

Marlin is right. Is your truck a manual or auto?

And you've got the 7.5" IFS up front.

Edit: Looks like we were all writing at the same time.

mojave joe
12-06-2011, 02:31 PM
Wow, you guys are great-
Thanks so much
The Truck is a auto...284k and running great (unfortunately, 280k of that was commuting to work)

12-06-2011, 02:43 PM
Because it's auto, I'd skip the 4.56 and go with the 4.88's. 4.88's don't stop me from running 75 mph all day long.

mojave joe
12-06-2011, 04:08 PM
What kind of rpm are you seeing at speed?

12-06-2011, 05:07 PM
Without going out and jumping on the freeway right now, I'd guess 3200-3300... can't remember off the top of my head. The 2.7 will not have any problems hanging at that RPM all day. Loaded up for the overland rally I drove 7hrs including mountains and returned a touch over 17mpg.

mojave joe
12-06-2011, 09:01 PM
That's good news. I'm constantly dropping in and out of overdrive at that speed. Thanks for the advice-

12-06-2011, 09:25 PM
No worries, good luck!

12-08-2011, 01:20 PM
The 8.4 is also a little more of a problem getting drop in units for, the places I called wanted my diff. to build rather than having one on hand to send me. It's also set up with side shims instead of spanner nuts for the carrier making it more of a pain to setup gears. I ended up just doing mine myself (3 different times because of ratio and locker changes) and never looked forward to it.

12-08-2011, 02:10 PM
How much does an average shop charge to make a change to 4.88 gearing? I'm thinking about having this done on my 3rd gen 4runner.

12-08-2011, 03:11 PM
Really depends on the shop and the cost of the gears, but you can figure about $1500 with parts and labor.