What 5 spd for AMX

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   I have 3:73 gears. The first is just way too tall. If I went any lower on the rear I’d be running 3500 rpm at 55mph...

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Bandana Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Jul/26/2016 Location: NC Status: Offline Points: 473	Post Options Post Reply Quote Bandana Report Post Thanks(1) Quote Reply Posted: Aug/28/2019 at 7:36pm
	I have 3:73 gears. The first is just way too tall. If I went any lower on the rear I’d be running 3500 rpm at 55mph...

purple72Gremlin Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16614	Post Options Post Reply Quote purple72Gremlin Report Post Thanks(0) Quote Reply Posted: Aug/28/2019 at 8:28pm
	way I see it. Either spend the money. Or forget it. Go buy a modern car then. Either way its going to cost money. Nothing is free. So come to that fact. If you want cheap, no such thing. Leave it alone if you dont want to spend the money.

farna Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19689	Post Options Post Reply Quote farna Report Post Thanks(0) Quote Reply Posted: Aug/29/2019 at 7:12am
	3.73 should be good with an OD five speed. Most use rear axles in the 3.55-3.73 range, a few as high as 3.23 -- depends on the OD ratio, trans first gear, and tire size.
	Frank Swygert

White70JavelinSST Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4867	Post Options Post Reply Quote White70JavelinSST Report Post Thanks(0) Quote Reply Posted: Aug/30/2019 at 4:28pm
	Remember there are four other gears besides that overdrive fifth in a 5 speed. The White70 is going to end up with a 2.73 axle ratio with the first gear in the 5 speed trans being 3.35. I estimate it will be turning about 1800 to 2000 rpm in fourth doing 70 mph with the tire. Fifth will be for very high speed. With a 390 having roughly 425 to 450 hp, I see no issues getting the car rolling. I know I know, I'm crazy but I'm going to try it anyway. with a 3.31 gear, first gear is like super low granny gear in a truck. It tachs out about 30 mph.... Edited by White70JavelinSST - Sep/23/2019 at 9:28am
	70 Javelin SST, second owner, purchased 1972

farna Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19689	Post Options Post Reply Quote farna Report Post Thanks(0) Quote Reply Posted: Aug/31/2019 at 2:16pm
	That's the problem I had with 3.08 gears and my AW4 -- had to be going over 70 to use 4th gear. With your five speed it's worse because of the low first gear. In my case the lower rear axle (3.55) made it take off better because first gear is 2.80 (I have the 87-90 0.705 OD mode instead of the later 0.750 OD). The torque converter is pretty low stall, but does make up a bit for the higher gear. Still, I picked up 2 mpg on average -- mostly from better in-town performance, I think. Mustangs with the T-5 used 2.73 rear axles in the 5.0L V8/T5 models with a 3.35 first gear. A 2.95 first gear would be better, but then you'd lose torque capacity in the trans due to the smaller diameter first gear. This is part of the difference between a NWC and WC T-5 -- the lower first gear to add strength -- NWC is 2.95 first. I really think a 3.31 axle would work better in my 63 Classic wagon, but it's not worth the money to change the gears for ~2 mpg. Takes a while to burn $600 in gas at 2 mpg... and I don't drive it enough any more, maybe 3K miles a year?
	Frank Swygert

Deans69 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Nov/24/2016 Location: Corpus Christi Status: Offline Points: 140	Post Options Post Reply Quote Deans69 Report Post Thanks(0) Quote Reply Posted: Sep/21/2019 at 4:41pm
	I'm doing a T56 to a 390 right now using the American Powertrain kit. I don't have enough room for the hydramax csc though. I did all the measurements but I'm coming up short.