aluminum d/s for IRS cobras

LEE93COBRA · Dec 27, 2003

Hey guys,

I installed 3.73 gears in my wife's 01 cobra yesterday. While I was at it I had ordered an aluminum driveshaft. Come to find out I received the wrong driveshaft. The company had sent me one for a t-5 trans. (yokes are different on the splined end of the driveshafts) After calling and speaking with them, I found out that FRPP does not make a aluminum driveshaft for the IRS cobras.

WTF?!?!?! I know some of you guys are running them, so tell me what kind are they? Are you running the ones for 96-03 live axle cars?

OleGrayCar · Dec 27, 2003

LEE93COBRA said:
Hey guys,
I installed 3.73 gears in my wife's 01 cobra yesterday. While I was at it I had ordered an aluminum driveshaft. Come to find out I received the wrong driveshaft. The company had sent me one for a t-5 trans. (yokes are different on the splined end of the driveshafts) After calling and speaking with them, I found out that FRPP does not make a aluminum driveshaft for the IRS cobras.
WTF?!?!?! I know some of you guys are running them, so tell me what kind are they? Are you running the ones for 96-03 live axle cars?

Hey Man,
You're not the first that I've heard who's had problems with the aluminum driveshaft swap, so I went and pulled my service invoice for the work when I had it done about a year ago.
All the work was performed by Team Ford of Marietta, GA......

According to the invoice, what was actually ordered and installed was "FMC part #- FMC 4602 aluminum driveshaft".

Now, I watched the Service Tech pull it outta the box and put it in, so I can safely tell you that no cutting, welding or extraordinary amount of hammering was required in order to get it to fit and I haven't had a bit of problem out of it since.

If you'd like, I'll gladly (well, maybe not "gladly", but I'll do it) go out in the garage in the morning and take a pic of either or both ends of it if you think that might answer anything that the info on the part # doesn't solve. Just lemme know what you need. For that matter, I'll hook you up with the name and work # of the guy who ordered and installed it at the dealership.....and if he can't help you, you've got problems.

Good Luck !!
-Dave
(aka OGC)

EDIT: double-checked to be sure and saw that mine has the #4602-J shaft also, so if your assembly stacks together anything like mine did, the yoke (on the tranny end) should end up mating to a T3650 looking something like this, lengthwise:

Joe Lynch · Dec 27, 2003

The 96-98 Cobra driveshaft is an inch longer than the stock IRS driveshaft. It will bottom out in the end of the transmission if the stack up of tolerances is such that the pumpkin is too close to the trans. Some people have used the alum shaft with no problems. You can see if yours is a candidate by unbolting your stock driveshaft, shoving it forward and measuring the clearance at the pinion yoke. If you have 1-1/4" clearance, the M4602J shaft may work for you without binding. If you have less than that, don't do it. There is no inexpensive alum driveshaft the correct length for the IRS cars.

Joe

LEE93COBRA · Dec 28, 2003

Joe Lynch said:
The 96-98 Cobra driveshaft is an inch longer than the stock IRS driveshaft. It will bottom out in the end of the transmission if the stack up of tolerances is such that the pumpkin is too close to the trans. Some people have used the alum shaft with no problems. You can see if yours is a candidate by unbolting your stock driveshaft, shoving it forward and measuring the clearance at the pinion yoke. If you have 1-1/4" clearance, the M4602J shaft may work for you without binding. If you have less than that, don't do it. There is no inexpensive alum driveshaft the correct length for the IRS cars.

Joe

The funny thing is, the aluminmum driveshaft assy and the stock driveshaft assy are the exact same length from mounting flange to yoke. BUT the yoke (trans end) on the stock driveshaft is longer than the aluminum one so I can't just change yokes out. In other words the aluminum shaft itself is longer but has a shorter yoke than than the stock d/s, so that both assemblies are the same length overall. This is why I wondered if the "J" driveshaft would work.

Dave--
FMC-4602 is the aluminum driveshaft that I have. There is a FMC-4602-G that fits 79-95 mustangs and there is FMC-4602-J that fits 96-02 live axle mustangs. I received the G by mistake and had thought about swapping it out for "J" to see if it would work.

-Lee

RAYS99COBRA · Dec 28, 2003

Not sure of the part number since the performance shop installed mine. I personally saw the guy pull mine out of a FRPP box and install it with no problems whatsover. Mine is a '99 with the T45, not the 3650 that's in your '01 so I'm not sure how much of a different it makes.

WALL96COBRA · Dec 28, 2003

RAYS99COBRA said:
Not sure of the part number since the performance shop installed mine. I personally saw the guy pull mine out of a FRPP box and install it with no problems whatsover. Mine is a '99 with the T45, not the 3650 that's in your '01 so I'm not sure how much of a different it makes.

Yeah the 3650 output shaft is bigger than the T45, so that's the reason why the 96-98 DS will work in the 99's. I was helping Lee93cobra when he tried to install the driveshaft and the first thing he noticed was the output shaft difference.

icemanp7 · Dec 28, 2003

i bought my aluminum D/S from a guy who said it was custom made from dynotech. he sold it to me for cheap( i think it was like 175 or 200) cause i think they are in the $400-$500 range if you get them custom. It works great and might be worth the money if you want to go that route.

LEE93COBRA · Dec 29, 2003

WALL96COBRA said:
Yeah the 3650 output shaft is bigger than the T45, so that's the reason why the 96-98 DS will work in the 99's. I was helping Lee93cobra when he tried to install the driveshaft and the first thing he noticed was the output shaft difference.

Actually Jonathan the t-45 and the 3650 shafts are the same. The t-5 is the one that is different and that is what JBF sent me. One for a t-5.

Since the 'G' shaft is the same overall length as my stock one, I am going to get a 'J' and see if it is the same length. I am going to use it if it is.

Joe Lynch · Dec 29, 2003

The J shaft is 45.5" center to center of the u-joints. Your stock drive shaft is 44.5", or one inch shorter. That is why you need 1-1/4" free play with your stock driveshaft before it bottoms out in the trans. Some people have it, most don't.
Joe

LEE93COBRA · Dec 29, 2003

Joe Lynch said:
The J shaft is 45.5" center to center of the u-joints. Your stock drive shaft is 44.5", or one inch shorter.
Joe

True..But IF the 'J' is like the 'G' the yoke is shorter to make up for the difference in shaft length. With the 'G' assy laying beside the stock assy (by assy I mean mounting flange and yoke that slides into trans) the overall length is the same. The 'G' is a longer driveshaft itself (by an inch) but the yoke on the aluminum is about an inch shorter than the stock, therefore overall assemblies are the same length.

I just hope the 'J' assy is like the 'G' but with the different yoke.

Lee

Lsredy2kstang · Dec 29, 2003

Well, I think that she has stated that is does not matter the size of the shaft, just the motion of the yoke!

Joe Lynch · Dec 29, 2003

I'm telling you that you must check the end play and make sure the driveshaft isn't in a bind. Do you think the output shaft bottoms out in the end of the yoke or do you think the yoke bottoms against a bearing in the trans? If the former, it doesn't matter what the length of the yoke is. This isn't the first time this question has come up.

Joe

LEE93COBRA · Dec 30, 2003

Joe Lynch said:
I'm telling you that you must check the end play and make sure the driveshaft isn't in a bind. Do you think the output shaft bottoms out in the end of the yoke or do you think the yoke bottoms against a bearing in the trans? If the former, it doesn't matter what the length of the yoke is. This isn't the first time this question has come up.

Joe

Ahh...Now I have seen the light...Thanks Joe.

Lee

Joe Lynch · Dec 30, 2003

Okie dokey, hope it works out for you.
Joe

aluminum d/s for IRS cobras

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