Looks like I'm not the only one, especially lately, that wants to do this swap. I only have two more quick questions: 1.) With the added weight of the T56 compared to my T5, will I lose performance in the quarter? 2.) Can someone please list manufacturers of the crossmember for me? I've seen Spohn's crossmember but too expensive, that is, if I want the driveshaft safety loop. Otherwise $100 isn't bad I guess.

 

I don't know about the weight slowing you down, but if you don't have atleast a 4.10 gear, you will notice a difference. I had 3.42's and my warmed over 350 (motor cam'd a bit high) did not like to get going. Ran great upstairs, just hated starting off. I went to 3.73's and things got better. I will be swapping in 4.10's as soon as I get time.

As for a crossmember, I got the one from SPD. Bolted right in and works fine. if you are thinking about a getting one though, order it now. It takes a while for them to send it.

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1992 Pontiac Firebird 350/Six Speed
1987 Toyota Pickup 383/500+ HP

 

Spohn has the cheapest crossmember that Ive seen. I have one sitting ready for install. Great looking piece. SPD has one and I saw some one else with one now but dont remember who. $100 isnt bad unless you can build one yourself.

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Mark Lock
- 86 IROC-Z - Torn down for 383/SuperRam T56 setup
- -= IROC Online =- - The site dedicated to the IROC-Z

 

You guys need to just take your old one to a welding shop. For 20 bucks they took my old mount pushed the center back the required amount and it works great. Only took the guy 20 minutes too!

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88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
SIX-speed
Eats LS1's with a 2.73 open rear and 2 1/4 stock catback

My Formula

 

Birmass, can you give me the dimensions of the piece, so I can have my old one chopped and re-welded? Would that ce cool for you?

 

I used SPD's crossmember...works good. I still had the BW 2.77 gears in my IROC and STILL waxed a stang with a fresh engine. My car isn't stock, but it isn't all that hopped up either. The gears work alright with the tranny but a 2.66 first in the tranny and a 2.77 in the rear just makes me wanna puke. It's all good though, I CRATERED my rear end (thought those BW rears were strong didn't ya). Broke one axle, bent the other, and sheared the gears...what a mess, I'm currently looking into a 3.23 ratio, that should come fairly close to the stock ratio it had with the, oh god here it comes, <gulp> 700R-4. Damn I hated that tranny. Good luck on your swap man.

Kelly

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If you've gotta fix it, fix it better than stock.

 

I'd go with higher (numerically) gears than 3.23 if I were you. That's what I have right now with the T56 and it still bogs like hell on takeoff. You need at least 3.73s to really enjoy that transmission.

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1991 Z28 - 350 TPI, T56, McLeod street clutch, ported plenum & runners, AFPR, Holley Annihilator ignition box and wires, Hooker shorty headers w/o AIR, no cats, Flowmaster muffler, homeade ram-air, SSM subframe connectors, Steve Spohn adjustable torque arm and T56 crossmember

 

What I did was take the old trans mount which was from a 700R4. I measured how far back the t56 mounting bolt was(about 4 inches back). That meant that the center section of the trans mount had to be moved 4 inches back. The tricky thing is that each side of the mount has different angles to fit the subframe. What the welding shop did was weld each side of the mount to a metal table and support it. Then they cut out the center of the mount. Even though the center was cut out, the sides were exactly at the right angles because they were welded to the table. Then he just welded new supports on the sides to extend the center section back about 4 inches and replaced the center section. You'll need some reinforcement too. The mounting hole should be oblong allowing for some play whe you install it. Also, make sure that when the crossmember is under the tranny, that it doesn't raise it too much. After having the crossmember made it held the tranny too high so I had to get longer bolts and spacers to lower the mount from the frame.


In other words it will go from a straight piece to a "U" shape so you can retain the same mounting holes. By welding the ends of the mount to the table the ONLY measurements you need are how far back the t56 mounting bolt goes. Mine was about 4 inches, but you'll want to install the trans, support it, and measure where the new hole location would go. I suppose you could measure before you install the trans but that might not be as accurate.

Hope this helps!

------------------
88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
SIX-speed
Eats LS1's with a 2.73 open rear and 2 1/4 stock catback

My Formula



[This message has been edited by Birmass (edited December 07, 2000).]

 

Do you guys think that my 3.42 rear will be okay with this tranny?

 

Yes, you'll be just fine. As yoou can see in my sig I'm using 2.73's right now. It REALLY sucks and is literally like I don't have a first gear, but it works. I'm gonna change them to 3.73's as soon as possible.

 

I'm so glad I have stock 3.73s

 

OH GOD, 2.73 SUCK *** !!! w/ a T56...I have had this combo for only about 3 months now and its driving me crazy.....I will definately be going to 4.10 in the near future.

On the bright side though, I went on vacation two weeks ago traveling from GA to RI and back and averaged about 31 miles per gallon doing about 70-75 mph w/ a 305 TPI....it sort of helped with those high gas prices in New England. I about had a heart attack seeing a gallon of unleaded go for $1.71.

 

Yeah, it's pretty bad. We average about 1.69 in the mid-atlantic. One of my pinion bearings has finaly gone and I'll be rebuilding my rear in the next week or so. 3.73's here I come!!

------------------
88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
SIX-speed
Eats LS1's with a 2.73 open rear and 2 1/4 stock catback

My Formula