Gearset Swapping for Higher Revs
Hello all, I had lost 3rd gear in my 83 and was looking for a newer tranny with limited slip and a better ratio than the current 2.20's with open differential in the back of my shark. And of course I found nothing affordable. But I want to go faster and I want Posi. Well I tear down the tranny and I had worn the dog teeth down on third gear. Ouch. I have a 78 tranny all in pieces, no reverse but with limited slip. In looking for tranny parts I had called 928 east and he said don't put the 78 tranny together your car will be slower. I said how? it has 2.75's instead of 2.20's,it's got to be quicker. He then told me that the 78 had taller gears in the tranny, and that really wiped out any advantage of the 2.75's because the final drive ended up being worse than the 2.20's. Little did I know that that would have been the key to this madness. So I call Jim Bailey to talk about options and what he had experimented with in the past, liking messing with ratio's and such. First I can't buy just the dog teeth I have to by the whole third gear. Over 700 bucks Ouch. So we start talking about options and we come up with "I've never heard about it being done but it should work in theory." 2nd 3rd and 4th gears in the 78 have more teeth than in my 83. That is why even though the 78 has 2.75's in the back it is slower than my 2.20's. because every tranny gear in the 83 has less teeth thus faster acceleration. But then Porsche puts 2.20's in the back to slow it down.(WHY) So I somehow get the dogteeth off the 78's third gear and it fits on mine. Yeah. Put all my tranny gears on the 78 pinion gear and they fit, even though the manual and all part numbers say they wont.(remember the cup is half full not half empty) and use the 78 ring gear and limited slip everything lines up except the last part. (of course) the tail shaft, well a little modifying with the dremel on some shims and it is back together. Pull out the manuals to adjust the backlash and it is done. Put it in the car and take it out. Now this is a stock 83 4.7 I take it out easy breaking things in and I find myself in fourth when I usually am in third. And things just feel weird. So time to get on it. Wow. 1st gear dump the clutch and go. and go and go Posi rubber all the way to redline shift rubber to almost 5,000 rpm's in second, hooks up, shift to third tires break free again. wow. doing like 15-20 in first, floor it tires break free and car will go side ways. Driving in second you step on it you get rubber. I'm sure I lost some top speed but I shouldn't be going over 120 anyway. :-) This car is like a new machine it is so fun from stoplight to stoplight. Yes I am so excited I can barely type. So Jim Bailey- in theory and in real life it worked. And also no howling from the ring gear and shifts great even with a preyed off dog tooth gear and dremmeled shims. It is awesome, if only I could of got borg warner sychros to work somehow it would be perfect. Now I may need a euro intake and throttle body ANYBODY? Let the madness begin
83s black/black LSD, I wonder if I could add 6th gear?
Well I took it down the turnpike tonite to see how it went in fifth gear, and that has changed also. My speedo went dead about a month ago so that makes it a little harder trying to figure out speed differences and such. I had my girlfriend following me in her car for awhile and here are some differences; before: 2,200 rpms was 85 mph now: 2,300 is 65mph 85mph is now 3,000 rpms big difference here. Jay you have an old bugger with 2:75's in the back what are your rpm's at 65 and 85 in fifth gear? In theory they should be the same as mine are now since 5th gear is a one to one ratio. I've driven a 78 though and I don't remember the rpm's beingthat high.
83s LSD with a crazy ratio thing goin'
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