Toyota IRS option

[mgb260]

Another option for TR4/TR6 and Spitfire/GT6 or any custom IRS for that matter(or my DeDion). 7.5" ring gear puts it inbetween Nissan (Datsun) R180 and R200. The IFS diff in 85-95 Toyota 4X4 pickup and Fourrunner. It has one short stub axle and one longer one. Simply mill the side with longer stub 6mm and use same seal as short stub side. Plug in another short stub and you have a compact narrow,strong IRS unit. I don't know if the 6 bolt pattern is the same as Nissan R200 and R230. You could use the same type adapter to VW type 2 or Porsche 930 CV. Very common and cheap in junkyards. 79-95 2WD rear 7.5" straight axles had ratios of 3.15 and 3.36(rare) 3.42 and 3.58 (more common)  3.73,3.91 and 4.10(most common). Tru-trac Torsen type or 4X4 lockers are availabe for this dif. Here are the pics:

[mgb260]

Another pic of side that needs to be milled 6mm and pic when done:

[mgb260]

Actually the Toyota 4X4 front CV axles are short,you would have to modify the end that goes through the hub(shorten and respline?). Also, ADD(Automatic Driveshaft Disconnect) axles use a smaller diameter stub shaft with roller bearings.they can be identified by the pneumatic control box on long side housing. You can change the bearings and seals and use the Non-ADD stubs.

[mgb260]

Toyota 2WD 7.5" desireable rear axle codes, the two numbers after the letter. Transmission  number right below.   29 in picture is 4.10(most common).  
                                                                       27=3.36
                                                                       30=3.73
                                                                       31=3.91
                                                                       37=3.58
                                                                       38=3.42
                                                                       39=3.15

[mgb260]

The 6 bolts in the drive flanges are pressed in and should be removed by pressing out with a socket in a vice. Replace with bolts and nuts to make CV axle changes easy. Also the rear 2wd carriers use larger bearings in V6 vs 4 cylinder models. Front IFS housing may or may not. Most aftermarket lockers and Tru Trac use the larger bearing size. OD is the same, ID is 45mm for small,50mm for large. Simple swap. This diff is the same as 82-86 Supra which had finned cover and different mounting.

[Moderator]

This is interesting stuff!

[mgb260]

Thanks Curtis! There is now another choice for IRS! These diffs can be found anywhere cheap. Plus who would have thought the IFS front diff gears and parts were identical to the rear 2WD axle. Lots of front diffs are reverse cut ring gears and if used in the rear would be weaker because the load would be on the coast side of the ring gear. Toyota must have figured it was strong enough for the front without the reverse cut gears. What amazed me was that the straight 2WD rear axle is a drop out like the MGB Banjo and Ford 8" and 9" and the gears and parts are identical to the front IRS with a cover. Here is a picture of the Supra finned cover all polished up like chrome. I'm thinking of making a sand cast  hot rod cover similar without the extra holes but with rear mount. The rear mount is similar to what Ford does on their diffs.

[mgb260]

Link to putting a 82-86 Mark 2 Supra clutch type posi in this diff:  http://www.4x4wire.com/forums/showflat.php?Cat=&Number=850240&page=0&view=collapsed&sb=5&o=14&fpart=1&vc=1   Also a link on installing a locker. You can also see why you have to replace the ADD stub.  http://www.toyotasurf.asn.au/techsite/frontdifflocker.htm

[mgb260]

Picture showing 86-95 IFS diff with long stub,non ADD:

[mgb260]

88-2000 2WD pickup 7.5" rear end manual trans 3.42 ratio,auto 3.58 ratios. The IFS is found in 86-95 4X4 Fourrunners,pickups and 93-98 T100 pickups. Most IFS are 4.10 or 4.30. About 6 of them on EBay for $50-200. Then do some junkyard shopping for the 2WD 7.5" drop out rear truck ratios.

[roverman]

Jim...are you eluding to an all wheel drive British sports car ? Say like "Roadmaster Unlimited " ?? crafty !

[mgb260]

Art, No. Don't give me any ideas!LOL. Just an alternative to the Nissan and Subaru units already  being used in Spitfire/GT6 and TR4/TR6. I did think about using two long stubs and making a Pro Street ,tubbed Bugeye Sprite with the widest tires I could find. I'm surprised you didn't think of that! Imagine with a Rover V8 and Blower sticking out the hood!

[WernerVC]

Did anybody build a cage to install this IRS under an MGB . pics please !

[Richard/SIA]

Took a while to relocate this thread.
Do we have a way to "Subscribe"?

That long/short setup may prove useful for another project, shaft drive motorcycle engine in place of a VW Bug rear engine and transaxle.
Still rear engine and I need a way to center it for weight distribution.
No relation to a British car but still fun if I can get it built.

[Richard/SIA]

OK, picked up two of these today.
Holiday half-price sale at P&P

Now find myself with questions.

First off, short side axle wobble!?
Does anyone know the fix?
When converting to a narrow center section as detailed by the OP do both sides then become liable to the stub axle wobble?
Seems it would be hard on seals and spider gears?
I nearly left the first unit I pulled at the salvage yard due to the short side wobble.
Second unit I pulled also has the wobble but not as much
This issue shows up on Toyots forums but there does not seem to be a solid answer available.

Second, both of the units I got have the ADD.
From what I can see this will not matter if  I am doing the narrow diff conversion, correct?
Seems I may want to get a third one of these WITHOUT the ADD.

My projects require a narrowed version for front engine cars with IRS and a full width version for the rear mounted FJR1300 motorcycle engine Tatum project which will also be IRS.
For the Tatum I will not want to modify the unit but will want to avoid the ADD.

I should have reviewed this thread to remind myself that there are two versions before going to the yard.
I suppose I could rig a way to just lock the axle collar in place, or run it with a switch to allow free-wheeling on demand, or a hidden neutral ant-theft device.

But for simplicity and lighter weight, does anyone have a log side without ADD that they no longer need?

[mgb260]

Richard, First I've heard of short side wobble. Makes sense though with high miles on 4WD. The ADD side has more support and uses a needle bearing. You could bore out the housing on the short side to fit the needle bearing. Or replace both sides with bronze Oilite bearings. I would coat either with moly(CV) grease.

[Richard/SIA]

If I am reading various threads correctly the ADD versions have needle bearings for the stub axles, which would be good as the bearing should be replaceable.
That should fix the wobble.
The possibly bad is that the axle does not use an inner bearing race, so a worn axle would have to be replaced.
I suspect the new axles cost more than a complete used diff.
I just bought a non-ADD long side axle tube on feeBay so I will be getting deeper into this soon.

BTW, unless I am looking at it wrong the R&P is revers cut.
Which is excellent for my rear engine project.

[mgb260]

Nope, not reverse cut. Newer clamshell type are reverse cut.That is why the 2WD pickup rear axle gears will interchange. I looked up the axle wobble issue. There is no support on the short side after the diff bearing. You would have to bore the diff for the needle bearing on that side. I wonder if there is a speedy sleeve to give a new surface on the axle shaft. There is a steel backed bronze bushing to replace the newer clamshell 7.5 needle bearing. Fits 86-04 but is $60 each.






http://eastcoastgearsupply.com/i-14472912-toyota-7-5-clamshell-bushingeliminates-needle-bearing.html



Here is a pic of the bushing on a later stub axle:

[mgb260]

This guys " Zuk's Gear Install" page has all kinds of info on setting up Toyota ring and pinions:

http://www.gearinstalls.com/supralsdtim.htm



Click on house on bottom of page for menu to other gear installs.

[mgb260]

Richard, Here is an idea for a mount for the diff. This was for a center mount 4X4 IFS done by BlazeN8 on Pirate 4x4 forum.

[Richard/SIA]

The more I learn of this the more confusing it becomes!

In your "Pic when done" at the top of the thread it appears you have inverted the diff.
Which makes sense to reverse the rotation from a front drive application.
But it would also put the pinion and drain plug at the top creating likely pinion bearing oiling issues.

Having already bought the parts I do intend to complete one of these conversions for a build based on GT6 running gear.
Tore one further down today and confirmed that the ADD units do use roller bearings on the stubs for both sides.
Also figured out how to reduce the size of the ADD unit while locking it into full-time drive.

I am also hoping to make a nearly stock unit work on a rear engine project using an FJR1300 Yamaha engine which has a "Reversed" drive-shaft rotation.
It becomes a "Correct" rotation again once the engine is reversed for rear mounting in place of a VW bug engine.
I need to look up the newer "Clamshell" version as I would prefer to have the reverse cut gears.

I know where to get a couple of early Spitfires cheap so may look into putting FJR engines into them if my first conversion works well.
Not really Brit-V8 I suppose, but 150 HP and 100Lb. torque at 7000 RPM and a 9000 RPM red-line should be plenty of fun in a stripped down car that got by with about a third of the power stock.

[Richard/SIA]

Confirmed that what I have is not reverse cut as I thought I want for the FJR and rear engine.
Front diff normal 4x4x orientation (Rear facing pinion flange), for rear engine, and not flipped.
FJR turns "Backward", but that gets reversed when I turn the engine around.
So unless I am confused I do want reverse cut gears for the FJR.

With 4.10 gears and turned around the 4runner diff will be excellent for a Spitfire/GT6 center diff project.

Looking around I found this link, http://www.f150hub.com/drivetrain/toyota-axles.html.
Looks like what I need for my FJR project may be a later 8" Clamshell type front IRS center.
Reverse cut gears and the 3.54 to 3.73 ratio I need should be available.

[Richard/SIA]

OK, now about the Toyota to Porsche CV adapters.
Where to get them?

My impression from the OP is that they should be readily available.
I have had no luck finding any currently for sale.
I have CNC lathe and mill so can make my own if I must.
With what I have to pay my CAD guy it's probably cheaper to buy from someone who is already doing them unless they are greedy about it.

If I end up making one set it makes more sense to make several.

[mgb260]

Reversed location was for direct drive to electric motor. I would replace the ADD axle with the non-ADD. There is a newer replacement needle bearing with a steel instead of plastic race. Most prefer the bronze bushing, much tighter. Did you check out the link on the diff  setups? The Supra guys probably have the Porsche adapters. I did the Nissan to VW Type2(bus) with 1/2" steel plate and dual bolt pattern. Planned to shorten VW Vanagon axles and have Dutchman respline. Maybe T100 axles with different outer CV end. Also 97-03 F150 IFS CV axles with Dodge Intrepid hubs for 5 bolt or Chevy Cobalt for 4 bolt pattern.

[Richard/SIA]

Ah, fudge!

I was going to mill the long axle side down today.
Seemed simple, clamp it down with the short side on the table.
But it is not that simple as the short side is as cast, so NOT flat.

Guess I will have to clamp the long axle side to the table, take a skim-cut from the short axle side.
Then I can use my new flat surface to locate on the table to do the long axle side.

Without having to pull the whole diff apart I am not seeing any better way to keep the edges square.
Since nothing is actually being bolted to the case after modification I suppose keeping it absolutely square may not be truly necessary, just very desired.