AUTO_X_AL

Well we are going to make the OD and on demand system and not an on request system. Then at least I can clutch in/out to save the OD. With a 3.54 and 25.6'' tires 128 mph is all you get out of 4th and that is 5900 rpm at that.

5900 is wwwwwwwwaaaaaaaaaaaaaayyyyyyyyyyyyy out of the power believe me!! Only throwing the switch on real long straight away's. With us normal use is the track! That's about it.

CentralCoaster

The 84 and 85 were all "on demand" overdrives. It's a shame GM screwed with it beyond that, they have no one to blame but themselves for the 4+3's reputation.

Dominic Sorresso

ZF-6 Trans-plant, along with the C5 brake upgrade, is the best change I ever made on my 84. Can't beat an internal rail shifter especially when coupled with Hurst shifter.

5speeds

A GM V8 T5 has the same bolt pattern, spline and same length input as the ST10 4 speed used on the front end of the 4+3.

The beam thing however is not that easy...but with good fab welding skills it can be done.

GRX

They are in fact (I know first hand) noisy but brutally strong. I still have the Richmond. It has about 100 miles on it. For sale! (whole kit).

Cadder

Just how noisy are these things? That's what I am planning to switch mine out to if the 4+3 ever goes out, which I don't think it will. Luckily for me, the previous owner completely rebuilt it about 5,000 miles back.

JLeatherman

GRX, what are you looking to get for the kit? PM me.

GRX

Actually it has less than 100 miles on it. A trip to Santa Cruz from San Jose and a few times around the block!! 1st, 2nd, 3rd.... sound like a reverse gear...not as bad but enough to anoy me. Kit was from Eckler's:
Tranny, shifter, speedo sensor. Let me estimate a price. Will PM.

anesthes

I was thinking rather than weld, mill a bolt on mount. The T5 with bell housing should be the same length as a 700R4. Looking at my setup on lift last night, compared to a T5 tail shaft I think a block of T6 can be milled for the verticle holes to the cbeam, and horizontal holes and depths to mount to the tail shaft. I figure just measure the driveshaft pinion angle of my current 700R4 setup, then set the lift up so it's resting on the mechanical safety's, and use my screw jacks to hold the T5 and dana in the correct spot so the same pinion angle is achieved. Then it's just a matter of hand milling and taking the peice on and off and on and off and on and off until it's the right size and holes are in the correct spot.
Once that's done, a 12-pack and a pizza for my buddy and he can write a CNC program for the part I make by hand.

Once that's done, all folks would have to do is bring the program on floppy to a CNC machine shop and pay for materials and a run on the machine.

That of course cures the cbeam issue. I'm still concerned about the shifter.

I can't do any of this now, it's spring but, once it gets cold again (november), I'll start playing. I have access to a T5 for mock up, just need the 4+3 bell housing, and I have a bunch of alum blocks and a small vertical mill in my shop. If nobody else does it between now and then, i'll start tinkering. Might happen sooner if my 700R4 blows up before then.. If so I really hope I can get *some* of my $500+ back on the torque converter..

-- Joe

SurfnSun

has anyone swapped a T-56 into a C4? Everything Ive read says its way to complicated to bother with.

anesthes

Complicated eh? Hrmm.

Only thing that concerns me about the T56 is the dimensions. Will it be too long, will it hit the exhaust, etc. The T5 should be more 'direct' as it bolts to the 4+3 bellhousing, is same length, etc.

Guess it's something to look into.

-- Joe

SurfnSun

yeah when I referred to complications...I was speaking to fitment issues.

JLeatherman

There is atleast one guy on here with a T56 in his C4. The size is fine. The only real complicated part is making a custom shifter cover cause the shifter is too far to the right. Gotta use the LT1 Camaro (93-97) bellhousing, clutch slave, flywheel, etc. Forget his name, but do a search in the C4 tech forum for T56.

SurfnSun

I wonder what ever happened to this and why it didn't come to market?

http://forums.corvetteforum.com/show...hlight=Keisler

AUTO_X_AL

Yeah but we dont use it much and I had just pulled the relay up to this point but some tracks will require more top end so this will suffice. And BTW the diffrence between the ZF and the 4+3 rebuild, for us, was time and money. I rebuild my spare tranny for $200 and still have another spare to rebuild for the next time I need one. The ZF is quite heavy as well. The guy that advised the rebuild over the replacement only sold me a cluster shaft and 1-2 shift cam. about $200 for both. He's also a very resourceful and respected name in racing in the detroit area. For some reason I really like the gearing and the way it works in the car.

Al

5speeds

By welding I was referring to fabricating a bracket. Since you have the original 700 or 4+3 why not just simply take some measurements and fabricate a bracket. The milling thing seems exciting and trick but.... take a good look and those lower bolt holes. It is much easier to take a 3/8 thick STEEL plate and make some spacers so that is it fastened to those holes, then do a 90 degree plate by weld on the top and bottom. Add some steel tubes for the beam bolts in between them to prevent the upper and lower areas from crushing. Take that off and have your beer buddy make a solid piece out of billet for resale to the hundreds of people who will want to do this conversion.

There is a BIG problem with people using tailhousings not designed to carry the load of these beams by use of brackets and other rigs. If the tailhousing flexes the bushing will wipe out. A T5 typically runs less then .003 of bushing to yoke clearance. The Mustang tail for example has holes that were used to mount dampner weights for harmonics while the T5 Camaro tail is better gussetted because it was designed for a trailing arm attachment.

anesthes

Thats why i was thinking of using an Fbody T5, because the fbody uses a torque arm to keep the rear end from twisting on launch and decel, so it should in theory be able to handle load. Infact, I think on a C4 application is would be under a little less load as the rear end doesn't rotate.

I'm not impressed by my 700R4/transgo/raptor combo, so I'm pretty sure this fall I'll take the trans out, and start a stick conversion. I'm kinda kicking myself in the *** for selling my lightweight flywheel, clutch setup, T5, etc last year.. Oh well.

-- Joe

CentralCoaster

Actually the rears on these do rotate. Some guys running high HP and slicks are twisting the 3rd member up and the torque beam is snapping the snout off. I doubt this would ever harm the trans though. It probably seems more forces at the end of the trans when bottoming out or hauling over dips in the road, when the weight of the engine+trans is bouncing around, held up in back only by the torque arm bolts.

Does the Fbody torque arm bolt to the trans or the chassis? Have any pics?

anesthes

I mean rotate as in part of the design, I know with enough force it sure will

The fbody torque arm bolts to the tail shaft of the trans, the fbody tail shaft differs from the mustang in that it has 3 bolt holes for the torque arm mount. (this is why i'm so confident in retrofitting a T5).

The transmission ALSO has a crossmember mount on the tailshaft itself (not the tranny) that is used as a rear engine/tranny spoort. When the car is driven, the rear end wants to rotate up and down so the tailshaft keeps it from rotating. The torque arm is similar to the cbeam on a C4, except that the cbeam is fixed, and the tailshaft is designed to move around. It's really a crappy design, but thats another story.

The tailshaft on the T5 is very similar to the TKO, infact, a lot of fbody guys replace exploded T5's with TKO transmissions.

Here is a few pix of a firebird I built right before I bought the C4. It should give you an idea of how the T5 setup in a fcar works. (this car was parted when I bought the vette cuz they're work more in peices)

http://members.cisdi.com/~anesthes/f-car-t5/23.JPG
http://members.cisdi.com/~anesthes/f-car-t5/24.JPG
http://members.cisdi.com/~anesthes/f-car-t5/27.JPG

Generally speaking, T5's are dirt cheap, and can be built to handle 500hp/tq (http://www.fordmuscle.com/archives/2...ild/index.php), so they could be a good replacement for a 4+3 IF the cbeam + shifter can be adapted.

As far as adapting the shifter, rather than cutting out the console I've seen shifters cut and welded so the handle is offset 2" to the left. (used on some 4x4 applications, and one guy on a T56 C4).

-- Joe

CentralCoaster

I don't get it, if the trans is bolted up to the torque arm, then the whole trans would have to move with the suspension travel.

Are you sure that torque arm isn't simply a trailing arm, and that there's a joint up near the trans where it pivots? If this is the case, then there is no torque exerted on the tailhousing of the T5. I agree that the C4 setup is too heavy to work well as it's designed. The most telling part is when you compare it with the C5, the C5 with rear trans puts less bending from weight on their torque tube and attachment points, not to mention it's way beefier.

Viper used a nearly identical setup to the C4 layout, I'm not sure if they moved the motor mounts back more, or have some extra support on the trans though.


On a side note, why is the floorplan trashed? Is that from jackstands?