salemetro

iTrader: (5)

I'll have to respectfully disagree. I have 2 8.8s in my shop, and have had them side-by-side each other. There is a fair amount of room to be gained...not huge...but enough to comfortably fit dual 2.5 pipes through the rear kframe without running too close to the CVs. Just about every 8.8 swap that I've seen has the pumpkin hanging low enough to potentially get smacked. Take a look at my build, and see for yourself how much clearance we were able to get.

I can only speak from what I have seen first-hand, and don't claim to "know it all", but the difference seems fairly substantial to me. Not to mention, the 7.5 has lasted in many of these conversions without issue. I guess that it all depends on how much power you want to throw at them. The weak link to me seems to be the axles.

Just my $.02

BLNLS1/RX7

iTrader: (2)

Nice project.

LS1-450

iTrader: (33)

Careful when you claim first (unless you're Martin). Also, the aluminum 8.8 housing can flex if not re-enforced where the steel 7.5 does not. The halfshaft is the weakest link. I have broken a stock Cobra half shaft, then the 1st upgraded alloy version sold by Martin & the second generation M5 alloy version sold by Martin that was deemed unbreakable by the manufacturer.

You are correct. The weakest points are the half shafts, as I have described above. Personally, I prefer the 8.8" due to it's lighter housing. Agree, that there are no recorded issues that I've seen regarding the 7.5. Even the T-bird CV's are good. I only damaged my 8.8 outer CV joint as a result of first having snapped the half shaft.

It is possible to get a 28 spline half shaft that is stronger than a stock 31 spline Cobra half shaft, due to material differences. I currently use the M5 28 spline half shafts in the re-enforced 8.8 housing.

KJT11

Well eventually i was going to flare the fenders and put some beefy tires on, the main reason i went 8.8 was the availability to me. What'd the 7.5 come out of? And how about would i get half shafts and a drive shaft without paying the 900$ to flying miata. I dont care to spend the money if the money is well spent.

salemetro

iTrader: (5)

I used a 7.5 from a v6 Thunderbird and put in a Detroit TruTrac. If I had gone 8.8, I would have used a Wavetrac (like my fbody). Axles ended up being a PITA, as people were claiming that axles from FactoryFive (8.8cobra swap axles, fit the 7.5 just fine) were the ones to use. Once we got the 7.5 mocked up, we found out that the axles needed to be extended 7/8" to fit correctly. New center bars and reassembly are costing me $700.00...still much cheaper than other alternatives (FM/V8R setups @ $1600.00)....and plenty strong with the new centers. Drawback is that I'm going to have to relocate rear strut mounts and pockets...but no biggie.

For me, the biggest issue was being able to fit the type of exhaust that I wanted....while still having strong axles and differential ground clearance. My solution was not the cheapest, but will work for me.

KJT11

Yea i could see how exhaust would be a hat trick, especially if your shooting for quiet, i think i might just end up running side pipes or something of that sort, axle wise i guess ill just have to measure twice order once.

LS1-450

iTrader: (33)

The 8.8 is an excellent choice. As noted, I prefer it to the 7.5 due to the weight savings. If that is what you have access to, go for it. It's a great rear end.

salemetro

iTrader: (5)

Absolutely agreed. It's not a bad way to go at all. As with all things, as I'm sure you'll agree, there are some trade-offs that can come in to play. The ONLY reason I'm not using one, is that I wanted more clearance for exhaust and did not feel the strength of the 7.5 gave up too much in that aspect.

blk mk8

lol martin actually called to ask how i did it.....so there goes that though, i am not sure if may be i cant remember how close i ran the exhaust but i built two cars with 8.8 setups. also both had mandrel bent exhaust so its hard to say. let me see if i can find some pictures of the two car. i just dont see a 7.5 having much more room. i could be wrong crazy crap has happened. i am sure there has to be some one else that also put an 8.8 out there when i did it. when i did i talked to martin and he said a 8.8 would not fit there. after i did it he called to see how it was possible, soon after it became common practice.

blk mk8

i searched the miata board and the car domain for the two cars there are no pics of the rear diff. funny after building the cars. i car about the chassis work and exhaust and mounts and most people see the paint job and big v8 under the hood and could care less about rear diff or exhaust routing

salemetro

iTrader: (5)

LOL Yeah, I know what you mean....for some people, it's all about just stuffing a big v8 into a small car, and they could care less about doing it right. I've seen some pretty bad hack jobs where the driver was just as happy as could be with it. On another note, if you're able to find pics of your builds....share 'em! I'd love to see them. As I learned a long time ago....there is more than one way to do a job....and I'm always game for seeing something different.

LS1-450

iTrader: (33)

Interesting. We did it in 03 & it wasn't that difficult. Surprised to hear that Martin had his doubts about it. Can tell you that I now use his M5 half shafts w/modified CV sleeve spacers.

The 8.8 is a larger pumpkin than the 7.5. Add the Cobra style cover & it gets longer, as well. As noted, I prefer it to the 7.5. However, the 7.5 will hold the power. The half shafts will go before the 7.5 does.

Since we're talking rear ends, wanted to add that the Detroit True-Trac is not as reliable as it was suggested to be when I bought in 06-07 abouts. The True-Trac has play in the gears. The drive shaft will dither back & forth a few degrees either side of center & it clunks. Clunk gets worse over time. Have had the whole assembly apart twice because just couldn't believe it was the True-Trac & not spline or spindle to gear play. e-mailed them about it & got no reply. Since then have found many others whom experience the same issues.

So, my advice to anyone using a posi diff is to try the stock trac-lock w/ the disks & just maintain the disks as required. Other option might be a locker of which is not as street friendly.

salemetro

iTrader: (5)

The other option (at more than 2x the price of the TrueTrac) is the Wavetrac. I would have gone that route in my 7.5m, if they made one for it.

blk mk8

ya back when we did it martin said there was no way to make it work. once i did it he called my customer and asked how i did it. it is no big deal as we all know, there are pics of the first and second car i built but like i said they have pictures of there brakes and engine bays with all the powder coating but no love for the hard parts. the second car still runs and drives up in the west palm area. the first one is rotting away at my brother farm. i have a motor and tranny ready to go back in it. once i do that i will put the diff back in it and take some pictures. it was a lot of fun building them and driving them. i wish i had build one for my self but as the building i got to drive them every once in a while. the first car now belongs to my brother as the owner sold the drive line and gave the car away when he moved out of the state. both cars had a mandrel bent exhaust. the first car had a single exhaust in the begining and it use to suprise people because it sounded funny and people use to think it was either turbo or a v6. they forget you can run single exhaust on a v8. we used drive shaft shop back when they where located in NJ. the first set of axles and hubs we made localy but we broke them after a few hard launches with drag tires and NOS. the second set held up pretty good, the formula for making the rear end work on these setups is way better now. back in the day if you did not use a 7.5 then you must have been using Voodo or some thing people told us.

djfury05

iTrader: (30)

Wavetrac comes with a lifetime warranty though.. well worth the price and piece of mind IMO!!!

salemetro

iTrader: (5)

Agreed. I use one in my Turbo'd F-body....unfortunately, they don't make one for a 7.5 currently.

KJT11

I dont know if anyone has ever seperated the Half Shaft CVs from the knuckles but they are the biggest pains ever. I got one side out by the grace of god and the passenger side i managed to break the knuckle , Now the bearings are so fried the car wont roll, so its on go jacks after i welded the knuckle back together (temporary). Horses ***

LS1-450

iTrader: (33)

The guys who have done the build probably all have. Don't even try to re-use it. Sounds like you tried to force the CV tri-bearing over the retaining clip. On the inner CV, the retaining clip must be removed first & then the bearing ***'y. will slide right off the spline. The outer can be done using a pipe to support the inner bearing sleeve. If you need more help, just do a search on "how to remove CV" or "how to remove half shaft." Yes, it's a pain in the a$$.

How's everything else going? Good job so far. Stay motivated.

KJT11

Yea i just grabbed it and growled but i have a knuckle on the way from FM's Salvage yard, and I am going to pull my dash tomorrow to start all my wiring and transmission tunnel fabracation for this weekend! More pictures will be on the way!

KJT11

This weekend i wanted to get the dash and subframe out so i could start on wiring removal and engine bay fab. Id like to know what people do as far as deleting old miata PCM wiring, I am going at it as cutting removing and heat shrinking the wires still in the dash harness, Any suggestions?

Got The dash out fine

This is kind of interesting i need to keep this a rolling chassis so my methods of moving it through my shop are kinda confusing


Test fit my dolly rig

My buddie Derek helped me move around the subframe since its awkward as it gets

Done on the lift, about flipped my miata off the dolly that was neat

Ride height of a truck

Now in theory i could just delete all wiring harness that this PCM harness connected too, In my head that makes sense.

So i started cutting and scratching my head mazda really makes some confusing wiring splices