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Ford 8.8 IRS Conversion


SUNNY Z

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How long are the GM CV shaft assemblies? 510 mm

Did you have new shafts made to fit,...? Yes, 345mm, and quite expensive!

 

The GM shafts from my donor car had one fixed and one floating CV. The high performance GM cars have two floating CVs so I'm having a shaft made with the spline for floating CVs on both ends. The Pontiac GTOs may have two floating CVs.

Edited by Boy from Oz
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Spent a little while doing measuring and scheming while I was rebuilding a CV axle and filling the diff before reinstallation.

 

So I came up with more chicken scratches. ... Can you tell I was doing CV things? (grease)

 

2012-10-08_21-32-33_660.jpg

 

This drawing is to scale- except for the frame portion of the car. Disregard any lines with x's through them. Sorryi its a mess, but this is the easiest way to convey my ideas at the moment.

 

So this is a drawing of the uprights (obviously). I'm thinking I'm going to have another set cut from 1/4" plate from my waterjet connection, when I get a good design.

 

The hole with the "+" in it is where I would cut a circle out of the upright, and install a sleeve, with a poly bushing (just an idea to make it a little less harsh and transfer less vibration). That is also just a tentative location of the mounts - not sure as i don't have a diff yet.

 

The R200 cover, and the 8.8 cover are both 3" thick from the mounting face, to the gasket face. The only difference being that the 8.8 has a larger ring gear, and will likely shift the carrier ~1/2" forward. I am thinking that I could make the upper horizontal portion of the upright longer, which would shift the "mount" further back, and then just accommodate at the bottom for the same amount.

 

The front face of the uprights are within 1/4" of the front face of the mustache bar, because it curves in in the center. Essentially with this design, the mustache bar would be completely eliminated and removed, thus putting more load on the uprights, and me wanting it thicker.

 

The bottom drawing is kind of what I have in mind with the "sleeve" idea. For those of you that aren't aware, THIS SITE is awesome for individal bushings.

 

 

/braindump

 

SUNNY Z:

 

It is significant to keep these posts up to date. For now I will use the Z31T CLSD R200, CV half shafts and beefy stub axles. I am VERY interested in the Ford 8.8 31 spline Differential as a replacement for the R200. The use of an appropriate rear cover for the 8.8 is a starting point for this conversion. Then brackets will need to be fabricated to tie down the nose of the 8.8 to existing Datsun 240Z structure.

 

In looking at your failed inboard shaft of the CV Half Shaft, it appears that it failed along the spiraled groove on the shaft. If these grooves were rolled in rather than milled in, that may explain introduction of a failure point due to the process of rolling in the grooves. Would be interesting to X-ray or Sonic test some of these shafts to see if a fault was introduced during the fab process. Then test some of these shafts that pass the tests.

 

Would be nice also to X-ray or Sonic test the 8.8 inboard shaft of the CV half shafts. Or figure out which shafts are milled versus rolled during manufacture.

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SUNNY Z:

 

Oops, made a mistake. The last sentence of my previous post should read:

 

 

Would be nice also to X-ray or Sonic test the Z31T inboard shaft of the CV half shafts. Or figure out which shafts are milled versus rolled during manufacture. Of note is that the drivers side shaft DOES NOT go through the CLSD clutch pack. The drivers side half shaft goes directly into the ring gear. The passengers side goes through the clutch pack. Still doing research on the Ford 8.8 IRS differential. The 31 spline Diff is used on the Trucks and the 28 spline is used on the cars. On the Ford 8.8 IRS Diff, I think the ring gear is on the passengers side, the opposite of the Datsun/Nissan. A complete 8.8 IRS Diff 31 spline with CLSD is EXPENSIVE. About the same price as I paid for the Z31T R200 Diff.

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SUNNY Z:

 

Oops, made a mistake. The last sentence of my previous post should read:

 

 

Would be nice also to X-ray or Sonic test the Z31T inboard shaft of the CV half shafts. Or figure out which shafts are milled versus rolled during manufacture. Of note is that the drivers side shaft DOES NOT go through the CLSD clutch pack. The drivers side half shaft goes directly into the ring gear. The passengers side goes through the clutch pack. Still doing research on the Ford 8.8 IRS differential. The 31 spline Diff is used on the Trucks and the 28 spline is used on the cars. On the Ford 8.8 IRS Diff, I think the ring gear is on the passengers side, the opposite of the Datsun/Nissan. A complete 8.8 IRS Diff 31 spline with CLSD is EXPENSIVE. About the same price as I paid for the Z31T R200 Diff.

 

Not sure where you're doing your shopping, or your reading.

 

I've covered in this thread what diffs were offered in what.

 

Some cobras had a 31 spline clsd that goes for ~$500 all day long. Also, the ring gear is in the same location... drivers side.

 

 

No offense, but please read a little more before you post. These threads get confusing when there's contradicting information.

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  • 3 weeks later...

Well I picked up a complete 04 cobra IRS with 55K on it last night for $700. Planning on parting everything that I don't need out, and having a reasonably priced pumpkin. Holy hell these 31 spline axles are HUGE. Not a huge update, but its a step.

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I went to the track about a week ago and cut few 1.6s and a 1.5 on my LS6/T56/Q45 280Z on Mickey Ts. I know

ColtGT4g63 was doing the same with his T56/Q45 setup. Do you think the diff being welded may have something to do the breakages? I was thinking that all that power is likely being transferred to the right rear wheel (right side axle the one that breaks?) under load snapping the shaft...maybe having the viscous coupling or some other sort of LSD would keep from loading up that right side too much? I bring this up because snapping an axle was on my mind after reading your thread then going to the track. I think the 8.8 is an awesome upgrade but I'm hoping us Q45 guys don't have too much to worry about ...lol

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Its the drivers side stub that always broke on my car. I hope your setup will withstand what you can throw at it, but I'm just done with the nissan diffs. To put a longnose lsd in the car would cost as much as this whole upgrade (hopefully), and you're still left with like 3 ratio choices, and limited availability. It just makes sense for me, because not only will it eliminate the diff, but also the stub axles, as I'll be going to a q45/z32 style strut assy (T3).

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I love the 8.8 idea (cheaper, ratios from 2.72 to 6.16, LSDs, lockers, spools, 31 spline axles, etc) and I hope you get it done and it turns out well. FWIW, the Ford trak-lok LSD kinda sucks. You might be able to shim the crap out of it to get it tight enough, but it isn't a torque sensing LSD like the Nissan unit. It's a sprung clutch unit. Seems like you're really just drag racing. You might look at a detroit locker, or even a spool. Spools are cheap and that's as strong as it gets. Don't know if they have one with the grooves machined for the axle circlips. Might be possible to do that machining after the fact.

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I love the 8.8 idea (cheaper, ratios from 2.72 to 6.16, LSDs, lockers, spools, 31 spline axles, etc) and I hope you get it done and it turns out well. FWIW, the Ford trak-lok LSD kinda sucks. You might be able to shim the crap out of it to get it tight enough, but it isn't a torque sensing LSD like the Nissan unit. It's a sprung clutch unit. Seems like you're really just drag racing. You might look at a detroit locker, or even a spool. Spools are cheap and that's as strong as it gets. Don't know if they have one with the grooves machined for the axle circlips. Might be possible to do that machining after the fact.

 

Yeah, I've looked into it, and it can and has been done quite easily. The trak-lok's have gained a lot of respect from me recently however - I have two friends with cobras that make over 800 hp to the tires, and they have held up to every bit of abuse they've given them, even on slicks. I'm quite excited to actually get this project rolling, but my student loans just came due (YAY) so most of my free money is tied up at the moment. I'll kinda be in limbo between selling parts and buying parts over the winter.

 

The Q45 diffs have the same size input stubs as an R230, which are larger than the Longnose R200. I HIGHLY doubt you'll have any trouble with those until you start making big power.

Edited by SUNNY Z
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I did some more measuring and pondering in the garage tonight.

 

Leaning more toward the explorer cover at this point, after measuring the diff and the car.

 

Looks like i'm going to end up blowing a couple holes in the uprights, and using these style bushings - different size probably as the bolts going into the cover are 14mm.

 

9-4101.JPG

 

However, I might need to beef up the uprights, or build some from 1/4" plate. I would then add a hefty brace to ensure no lateral movement.

 

 

The bottom of this picture would be where the diff would mount, putting the upright in the middle, and having a bolt captivate the assembly from the back side.

 

Mounting in this fashion will make the centerline of the axle roughly 5" in front of the upright. This will be OK, because the R200 axle centerline is roughly 4" in front of the upright, and there is a rearward facing angle to the axle - if you follow that. Meaning the axle centerline of the diff is to the rear of the axle centerline at the hub. I will also be mounting the diff about 2" (guess) higher, to accommodate for my car being lowered.

 

 

 

These bushings are $23/pair on suspension.com, making them quite affordable.

 

Here are the front ones i'm going to buy, unless suspension.com has them - which they might - as this diff was used in several applications.

 

http://cgi.ebay.com/...atchlink:top:en

Edited by SUNNY Z
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Since it seems I'm only posting here to keep a record of what I'm doing.......

 

I pulled the diff and axles today so I could do some test fitting with the 8.8. This is going to be a fairly straight forward swap it seems. With the pumpkin as high as it can go before it hits the frame of the car on the cover, it is exactly level with the centerline of the outer axles at static ride height. This is excellent, because before, my axles were at ~an 8 degree decline towards the diff. It could easily go up another 2", but that would require the cutting of the frame, and I don't think its at all necessary in this application. I plan on taking the cover and uprights to my dad's shop this weekend (home for thanksgiving) and further bracing and prepping them to accept the diff mounts.

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Sounds like it should work pretty good, reducing the angle in the joints will be a big plus. Are you not worried about just moving the weak link out to the stub axles? Thats the reason I kind of decided to go SRA, because I didn't want to spend the money to get strong axles only to move the weak link to the stub axles. Maybe you have the billet stub axles now so you will be good, although I know someone has broke the billet stubs, but he had a LOT of power.

 

-Will

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I'm going to be selling everything I have, and using a TTT strut housing, that allows the use of a Z32 / Q45 style axle and brakes. The outer shaft on a Z32 is acutally 2mm bigger than the ford outer, at 33mm IIRC. I was afraid that I might break the stubs, so I decided to eliminate them all together. Also, I'll be able to switch from 4 lug to 5 lug with only one nut per side! ... (if i ever wanted to)

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I was able to get the rear mounts finished while I was home for thanksgiving.

 

I ordered a pair of poly bushings off speedway motors (best speed shop in the midwest), and got them before thanksgiving.

 

Here is the speedway PN: 91634545,

Link: http://www.speedwaym...hing,58411.html

 

I had already measured everything, and marked the uprights for the holes, so I found some pipe the right ID, and traced it onto the uprights.

 

I then cut it out with a plasma cutter, and tacked the spools in place, allowing for the diff to be 1/2" in front of the uprights, as I'd measured for in the car - which allows clearance between the cover and the frame cross rail. I went ahead and welded both sides so it would look a little nicer and be strong to boot!

 

Here is the result!

 

2012-11-23_14-45-42_720.jpg

 

2012-11-23_14-45-25_878.jpg

 

2012-11-23_14-45-10_127.jpg

 

2012-11-25_20-40-30_869.jpg

 

2012-11-25_20-37-41_479.jpg

 

2012-11-25_20-37-19_489.jpg

 

2012-11-25_20-36-56_344.jpg

 

The front bushings showed up while I was gone as well, so I'll be mounting this assembly back in the car, and doing some more design for the front mount. I'll probably copy the style of the TTT mount. It looks pretty good.

Edited by SUNNY Z
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