JMortensen Posted July 17, 2009 Share Posted July 17, 2009 Background: 5.3L X Prepared autox car, is being built to the full extent of my capability to build it, no holds barred. Right now the chassis is pretty much done, need to finish up some odds and ends on the suspension and bolt it back together and plumb brakes and fuel and electrical. 5.3L from a truck ready to go with 27K miles, bone stock. Still need to change pan for the engine and figure out whether to do FI or carb. Cam/spring/pushrod upgrade planned. I've sold some parts and rubbed some nickels and I've got $$$ for a transmission. I have about $3K. So the question is, do I go with a remanned upgraded Keisler T45 or a used T56. Here's my list of pros and cons for the T45: PROS: New synchros, bearings, etc 5 speed is lighter (weight is king for autox) Don't have to screw around trying to find bits and pieces, it's all there May not have to deal with tunnel clearance issues CONS: Wide gear spacing will probably make 1st unusable Only 25 lbs or so lighter from what I understand Probably a lot more expensive than T56 with all the bits to get it installed. I see T56's going for ~$1500, but not sure how much flywheel/clutch/pp/hydraulics/shifter/driveshaft adds to the total. http://www.keislerauto.com/index.php?/vmchk/mopar/mopar-bare-transmissions/5-speed-manual.html So what do you guys think? I'm torn because I really like the gearing on the Camaro T56 better but it is heavier and I'd have to find one and all the parts to get it installed, etc. Then what if you get a used one and it needs synchros or something. That would be a real bummer. This thing would be lighter, come on a pallet with all necessary parts, and be remanned. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 17, 2009 Share Posted July 17, 2009 All the finer details aside. "No holds barred"" "Weight is king" The decision is right there. Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted July 17, 2009 Share Posted July 17, 2009 Sounds like the only real down side to the T45 is the gearing. So forgive me if this is an obvious thing I don't know about. Why not change the ratios in the T45 and have it all? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 17, 2009 Author Share Posted July 17, 2009 Not listed as an option, so I'm guessing it's not possible. I suppose I haven't asked yet. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 17, 2009 Author Share Posted July 17, 2009 Just playing around with the transmission calculator and it looks like the jump from 4th to 5th is pretty wide on the T45 too. The 6th on the T56 is useless, but the 5th is a more realistic .74 vs .67 to 1. Quote Link to comment Share on other sites More sharing options...
tube80z Posted July 17, 2009 Share Posted July 17, 2009 Background: 5.3L X Prepared autox car, is being built to the full extent of my capability to build it, no holds barred. Right now the chassis is pretty much done, need to finish up some odds and ends on the suspension and bolt it back together and plumb brakes and fuel and electrical. 5.3L from a truck ready to go with 27K miles, bone stock. Still need to change pan for the engine and figure out whether to do FI or carb. Cam/spring/pushrod upgrade planned. I think you forgot track days in your analysis. Because if all you really want to do is autox I'd recommend a richmond dog-ring 2-speed. Mucho lighter. With the v8 you're looking at running in mostly a single gear. What you'll need to do is have a couple of rear gears to pick speed ranges that work best (one gear to 70/75 MPH). From my experience this is always faster than shifting and much easier to drive. Things happen very quickly when you prep to this level. Backs are broken etc. I can see having more gears for track days, which I think you want to do. I'm going with a Muncie or a ex-NASCAR dog ring 4-speed and will change rear gears. But with no overdrive you'll need a steep rear end to make 150 or so. Cary Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 17, 2009 Author Share Posted July 17, 2009 You're right Cary. Track days are part of the plan later so I already ruled out 4 speeds because I figured out with a 3.54 I'd top out at 125 mph, which just isn't enough top end. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 17, 2009 Author Share Posted July 17, 2009 Did some more checking and it looks like I can get to about 60 mph in 2nd with the 5 speed. For 70-75 I really need the 6 speed, difference being the 2nd gear ratio of 1.99 vs 1.78:1. That's assuming I'd use commonly available R200 ratios in the rear. Quote Link to comment Share on other sites More sharing options...
zed240au Posted July 19, 2009 Share Posted July 19, 2009 hi dont know if anyone does it over there but here i australia have guy changing ratios in t56 boxs not cheap but it you want to get ratios perfect could be worth it ratios they have are list on there site http://www.malwoodauto.com.au/ mick Quote Link to comment Share on other sites More sharing options...
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