I just ordered my base kit

[RickGT40]

Now while I wait I need to find a donor. The plan is to find a '94-'95 5.0 5 speed, but I have a question. Can I use the T5 transmission from a V6 with a V8? I read somewhere that there are differences, but I don't know if that means it won't work. I see ads for cheap V6 5 speeds and cheap V8 autos. I can get 1 of each for less than the 5.0 5 speed cars I can find so far.
I also have a question about the rear. I ordered the IRS rear, and I have the Lincoln unit already. Should I consider putting in a limited slip diff? What rear ratio should I consider? The Lincoln rear is an open diff 3.07.
Thanks for reading
Rick

[Bren]

I can't speak to the donor tranny/engine combo, but I know a lot of people use Tremec T5 transmissions with their v8's. If you're producing enough power, you may want to consider an upgrade.

As for the rear end, I would definitely go with a limited slip. (I don't have my car on the road yet, so I'm not speaking from experience.) If you're spinning the rear wheels, you want both to spin. You're going to have to (or at least really should) rebuild the rear end anyway, so you might as well upgrade to a limited slip. I researched it a while ago and know it can be done. I think a tab inside the pumpkin has to be cut off or something. Others would know more about it, but I know it can be done. Me and a good portion of others use a 3.27 ratio, a few use something as low as 3.07. Most people run 3.55, and some run higher (3.75, I think). Search this forum and the other one (ffcars.com) for discussions of rear end ratios. It will be determined based on the gear ratio in your tranny and the horsepower/torque of your motor.

By the way, I've got a 611 hp engine and a 0.83 (ish?, I don't remember exactly) 5th gear.

[Jeff Kleiner]

There are numerous versions of the T5; the V6 version is somewhat weaker and probably won't last long with a V8. You can convert the Lincoln 8.8 to limited slip. This requires changing the ring gear carrier and all of the internals associated with it. By the time all is said and done you might be ahead $$$ wise to find one from a Thunderbird Super Coupe that is already equipped with limited slip. As for gear ratio like Bren mentioned there is no one size fits all type answer...your engine and transmission choices play into it. Let us know what your engine plans are as well as what the 1st. gear and 5th. gear ratios are in the transmission and we can make some recommendations.

Cheers,
Jeff

[trublue]

Rick,
Sounds like you are getting the Mark 4 Roadster. Congratulations! The next year or two will be fun, I can guarantee that. If this is your first, the donor route is a smart decision. I elected to go with a 4.6L V-8 from a 2000 Mustang GT (72K miles) for my Mark 3. The disassembly process really helped me. That was in 2006. I was able to use everything I needed for the build from that one donor. It has been a joy on the road and never fails to start. Electronic fuel injection is both reliable and very powerful, with great fuel mileage and torque. I attended the Mott College weekend Build School on the 4.6L. It was an invaluable experience for me. It convinced me that I could do the job myself. It also affords the student builder the chance to ask all those questions, YOU have, to truly expert instructors. Best of luck. The forum will be your best friend in the months ahead.

[skullandbones]

Hi Rick,

I, too, went with the basic kit but did some upgrades like tubular control arms, coil overs, aluminum radiator, etc...... I also did a donor pallet which in theory is good. It didn't work out for me since I didn't do enough research and ended up with some components that I would replace almost immediately. I have a suggestion that you might consider. Instead of a single donor why not do what I ended up doing sort of accidentally. Choose the donor components from several donors. It will be more economical and if you choose wisely, they also will be very serviceable. I ended up changing out my 92 GT diff for a 95 Cobra diff. I went with a crate 302 and installed power adders that I had gotten great deals on. Some of the parts from the original donor pallet were quite good. The gas tank, drive shaft, alternator, PS pump and rack, bell housing, fork, and a few other items. However, if I had been a little more patient and "cherry picked" as I like to call it, I would have saved some money and gotten better components. One donor doesn't usually have everything you want. Some will say you have to rebuild everything. That's not true if you get a good condition item in the first place. Do your homework and I'm sure you will find the right stuff for your project. Plan your gear ratios ahead. It may be worth it in the long run to get a new trans that is geared perfectly for your project and then mate it to a 3.55 or 3.27 diff with posi traction depending on your HP and use of the car. I have a T-5 with an overdrive that must be around .65 so my 3.27 is a little too high for that. In my case, a 3.55 would be about perfect or add more HP. You can see what we've been talking about regarding gear ratios from that example. I don't believe there is a perfect combination for all types of driving but you can get pretty close initially so you won't have to replace to much to get it right. I will probably change the ring and pinion in mine pretty soon which is $200+ if I do it or $500 if a local shop does it. Good luck, WEK.

[68GT500MAN]

Welcome and congratulations on the purchase.
Doug

[RickGT40]

Thanks for the encouragement and information.
Let me expand some on my plans. I want an engine that makes about 350 hp, a manual transmission, and a good handling cruiser, on a budget. I will rebuild the engine as needed and put on a new top end kit.
I have done research on the T5 and see that the V6 version is rated for 265 fp torque compared to the V8 version's 300 fp. I also know that the 5th gear ratio is different. I would prefer the V8 version but want to keep cost down.
I have also looked into the LSD situation and have read that the diff for the irs has a recess cut into the spider gears for the spring clip on the end of the axle. The solid axle diff uses a c-clip on the inner end of the axle to retain it and I am wondering if the space for the c-clip provides space for the spring clip on the IRS.
Rick

[CraigS]

I "believe" you need an IRS specific center section. I would also recommend trying to find a diff w/ the correct ratio and LS if possible. Look for 327,331 or 355 ratios. If you can get the right ratio, changing the center section isn't that hard. You would want to get a pack of side gear shims so you can set the backlash and preload. Only tool needed is a dial indicator. If you need to change ratios that is best done by someone w/ experience and all the proper tools. The V6 trans will work for a while depending how hard you are on it. If you can get a near freebie go for it. Trans can always be upgraded later. OTOH, get on some of the Mustang forums and find the local club. There are thousands of them out there and cheap parts left over after a guy upgrades his Mustang are quite common.

[RickGT40]

I did a little more Investigating and found out that the spider gears for a IRS diff have a bevel on the ID for the clip on the end of the axle. The solid axle spiders are square cut on for the c-clip.