Is it just me or does it seem putting a viper tranny in even with this "adapter" seem like it's going to be a 4k job with a ton of work involved???

The F-Body T56 as jim I think was trying to point out would be a much more worthwhile venture.

 

More fun facts... the LT1 T56 uses a clutch fork with a remote slave cylinder (like the RX-7) to actuate the clutch. The LS1 T56 has a hydraulic throwout bearing.

The T56 is about 10 lbs. heavier than the Mazda 5-speed by my scales... 112 lbs. dry for the Mazda, 122 lbs. dry for the T56.

The '94-up T56s have a 40-tooth reluctor on their electronic speed sensor (40 pulses per driveline revolution) and you'll need a box from Dakota Digital to adapt the raw output of the VSS to the 8,202 ppm @ 60 mph that the FD speedometer is expecting... unfortunately the part ("SGI-1", I was told) is out of production, and I'm having a hell of a time getting Dakota to cough one up myself.

Also, the T56 is physically shorter than the Mazda 5-speed. On the back of an LT1 small block, it lines up with the stock shifter opening. On the back of a rotary, even with an adapter plate... well, see for yourself. The shifter will likely end up about 2.5-3" farther forward, which could prove an interesting hurdle to overcome.

 

They should use these trannies on the 20B conversions that move the firewall back. Nice way to compensate for the relocated engine. Imagine that, single turbo 3 rotor that maintains the steering geometry, 600HP, 6spd manual, and the shifter is actually in the right place, woohoo. Hmm that sounds like another car i heard about...

 

So Jim are you saying that this can't be done w/o extensive modification

 

Possibly. Any attempt to integrate a totally foreign (to the original car) piece of equipment usually means a lot of work.

In this case, you've got transmission length (new or modified driveline), shifter position (custom solution?), elimination of the PPF (requiring a transmission mount and something to support the differential and set pinion angle), and the electronic speedometer (conversion of the VSS signal) to think about. Not to mention the reverse lock-out solenoid (keeps you from making those embarrassing 4th to Reverse power shifts).

If Dakota Digital will get their act together, I'll have a solution for the electronic speedometer. Mine was recalibrated to 8,000 ppm @ 60 mph when I was planning on using a GM PCM (which can be reprogrammed to output that figure) which doesn't help much. At 60 mph, with P275/40-17 tires (a fairly common size) the tires will be making about 786 revolutions per mile, by my calculations. Factor in the 4.10 differential, and you've got 3,222 rpm at the driveshaft. With a 40-tooth VSS on the T56 (40 pulses per revolution), the raw output is in the 129,000 range, which means you'd need a device capable of dividing the signal by about 16.1 (129,000 / 16.1 = 8,012 ppm) for my application, and 15.7 (129,000 / 15.7 = 8,216 ppm) for the stock FD speedometer. Dakota Digital's SGI-5 is only capable of a maximum 2.0 division...

I've also devised a schematic for handling the operation of the reverse lockout solenoid, which is unlocked (allowing a shift to reverse) by the GM PCM at ~5 mph. By using a set rpm instead of mph (requiring a single wire hookup) and a couple relays, you can duplicate the operation very closely, but you need an rpm trigger. My original thought was to use an MSD rpm switch, but you'd need a custom module in the 1,000 rpm range (5 mph with 2.97:1 first gear, 4.10 differential, and P275/40-17s = ~1,000 rpm) and I'm not sure, based on other recent interaction with MSD, that they'd cough one up. I did find a web site which details making your own custom rpm resistor, however. And then realized that I have an engine management control system with at least two and possibly three rpm-triggered outputs (FAST SEFI-8LO) for controlling a nitrous system, and that I can set the rpm level anywhere I want, because it's fully programmable. Problem solved, although the MSD rpm switch idea would still work, and there was another device (Apex'i Rev/Speed Meter) mentioned that has a speed or rpm triggered output which might work also.

So a transmission mount is no big deal, and supporting and aligning the differential, while a little work, is no big deal either. What about shifter location? I don't have to worry about it, but someone trying to use a T56 with a rotary will. The bellhousing of the F-body T56 is about 4.9" long. The distance from the front of the transmission case to the shifter is 23.9" according to the data I've seen, so from the front of the bellhousing to the shifter, you're talking ~28.8", and unfortunately, there's no alternate shifter location farther to the rear. I'd guess it's about 3-4" short of the location of the shifter on the OEM 5-speed. Add in a 1/2" adapter plate (for sake of argument) and you still have 3-3.5" to make up. Unfortunately, this might be the straw that breaks the camel's back, at least with a T56, since the shifter stub of the transmission extends above the transmission tunnel sheet metal when properly aligned, meaning there's no clearance for some sort of linkage or "L" shaped shift handle, unfortunately.



The Tremec TKO and TKO II 5-speeds are even shorter (but lighter, and FAR stronger) than the OEM 5-speed, and from the front of the case to the shifter, it's only 19.5" to the shifter in the rearmost of 3 possible locations. Even with a 7" bellhousing and adapter plate (input shaft is 7.2", I believe), you're still at 27", almost 2" less than the T56. The T5 5-speed, although why anyone would want one is beyond me, is ruled out by default... it shares most of the dimensions of the TKO.

So how about the Richmond 6-speed? It's input shaft is 6.6" long, so let's assume a bellhousing and adapter plate exist to work with that. From the front of the case to the shifter's centered position is listed as 20.75". Once again, you're talking 27-28". Notice a trend developing here?

The Richmond also has external shifter linkages that might cause a problem with clearance. I'd stick to internal rail shifted transmissions for something like this.

So there you have it... several obstacles to overcome, not the least of which is how are you going to shift a transmission with the shifter located somewhere around the front of the stereo. Does that make it impossible? No. But it certainly doesn't make it easy, and things that aren't easy usually aren't cheap either, I've found...

 

Thanks for the lesson Jimlab, looks like I'm going to stick with the stock tranny and build it to take the torque. Any suggestions? By the way I will probably be using 4.30 gears with the rebuild

 

Um, kugan found someone who already makes an adapter.. And has them in stock.... He posted it in the 20B section..



-Zach

 

who sells tremec tranny's for cheapest? new or used.

 

awesome.

 

this one is for redtt.i found ur cheap viper tranny.guess where.vipercarparts.com.this is also for jim.i emailed them and asked how much for their trannies.1000 plus freight.

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.... prices and specs on the transmissions u have in stock?

Out of trans for now.

$1000.00 when we have one plus freight.

Check back in 30 -60 days for new inventory.



480-610-1202
Viper Car Parts Corp.
1025 West 1st Ave.
Mesa AZ 85210

Exclusively selling Viper Parts since1996

Viper Chris

www.vipercarparts.com

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thank u very much.i guess that is where u can find it.

 

Great. Now add in a special flywheel, clutch, and probably an adapter plate to get it to bolt to the back of a GM engine...

 

yeah i hear ya jim.thats why i say go with the f-body t56.im sure u could buy a stage whatever clutch setup for the same price as an oem viper setup.

 

Jim.. ( or anyone )..

So, your looking at 28"... what is the length to have it align in the center? Whats the length? 30"?

Mike

 

Has anyone looked into how strong the RX-8 tranny will be.
Perhaps if your looking for 6 speeds and a bit stronger tranny the new rx-8 6 speed will be the way to go. I'm not sure it'll be much stronger though. It should be a lot less headache. Perhaps it'll just swap right in and add 25% in strength. For may of us that will be well worth the 1500$ or so the whole job may cost.

 

do any companies make straight cut gears for the tremec?