Grapejuice1998 Posted March 21, 2016 Share Posted March 21, 2016 My SS454 Monte seems to have a set of reeeaaally steep gears in it. It turns right at 4k rpms @ 70mph. I was thinking of going with 3.55's? Discuss. Quote Link to comment Share on other sites More sharing options...
502ci Posted March 21, 2016 Share Posted March 21, 2016 How tall are your rear tires? If they are 27" that would show you have maybe a 4.56 gear...which is way steep. I am pretty sure 3.55's are a Ford gear ratio. A GM comparable would like a 3.31 or 3.42. Do you ever plan on an overdrive? 1 Quote Link to comment Share on other sites More sharing options...
MCfan Posted March 21, 2016 Share Posted March 21, 2016 I'm sure many various ratios have been tried in our SS454s but I have only heard of two being shipped from the factory: either a 2.56 or a 3.31. My '70 has the 2.56 and the best thing I can say about it is that it makes a good low rpm cruiser, even with 245/60s. On the other hand, I wouldn't consider anything steeper than a 3.31 for street/highway use and then I would run a 28" tall tire like a 275/60-15. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted March 21, 2016 Share Posted March 21, 2016 I like the 3.31 or 3.42 1 Quote Link to comment Share on other sites More sharing options...
Leghome Posted March 21, 2016 Share Posted March 21, 2016 My 72 has a 700R4 and 3:73 gears and it runs 2,700 rpm at 70. 1 Quote Link to comment Share on other sites More sharing options...
502ci Posted March 21, 2016 Share Posted March 21, 2016 My SS454 Monte I just noticed the SS part...are you keeping it original? Then the overdrive I previously mentioned is out the window. Quote Link to comment Share on other sites More sharing options...
bigscaht Posted March 21, 2016 Share Posted March 21, 2016 3:42s are a pretty good gear set 1 Quote Link to comment Share on other sites More sharing options...
Grapejuice1998 Posted March 23, 2016 Author Share Posted March 23, 2016 Sorry to be late getting back to the thread, but I have red each reply. I'll take a video and post it, of the rpms at 70mph (which I have verified with gps). The rear tires are 235/70/15. I tried marking the tire and counting the driveshaft rotations vs 1 revolution of the tire. It came out about 3.75:1. Not sure if that's accurate, but I can't believe a set of 3.73 would run 4k at 70. Quote Link to comment Share on other sites More sharing options...
502ci Posted March 23, 2016 Share Posted March 23, 2016 I'll take a video and post it, of the rpms at 70mph (which I have verified with gps). The rear tires are 235/70/15. I tried marking the tire and counting the driveshaft rotations vs 1 revolution of the tire. It came out about 3.75:1. Not sure if that's accurate, but I can't believe a set of 3.73 would run 4k at 70. Speedometer not work? That would be a 28" tall tire. If you did it correctly and it came out to 3.73 (which it sounds like you did) yes it is impossible to be revving at 4k. So either your GPS is not accurate, you messed up on the old school way of measuring the gears, your tach is not working properly, or your transmission is slipping bad. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted March 23, 2016 Share Posted March 23, 2016 if it is a factory dash tach...I have seen many, many, many of them way!!!! off a 28" tire and a 3.73 at 70 should be in the neighborhood of 3400 rpm, so 4000 on a factory tach doesn't surprise me Quote Link to comment Share on other sites More sharing options...
Grapejuice1998 Posted March 24, 2016 Author Share Posted March 24, 2016 Traffic didn't allow me to get all the way to 70, even though it looks like I did. The angle of the camera lies. https://youtu.be/PIAAAPKVI4o Quote Link to comment Share on other sites More sharing options...
Grapejuice1998 Posted March 24, 2016 Author Share Posted March 24, 2016 Speedometer not work? That would be a 28" tall tire. If you did it correctly and it came out to 3.73 (which it sounds like you did) yes it is impossible to be revving at 4k. So either your GPS is not accurate, you messed up on the old school way of measuring the gears, your tach is not working properly, or your transmission is slipping bad. The speedometer works. I just verified it's accuracy with my gps app. Quote Link to comment Share on other sites More sharing options...
joseph Posted March 24, 2016 Share Posted March 24, 2016 hello all, i thought i had 2.73 gears ? in my 1970 ss. i put in 3.73 ( like most chevelles ) i run at 60 mph and the tach is 3,000 . it sounds great and the stock cam is by the power curve . i have b p goodrich p225/70r15 m+s tires on the stock rims. the last time i went 70 mph i want to say the tach was almost 3600 to 4000 rpm. i think if you put in a 700r4 the rpm goes down 1,000 rpm ?. i want to keep mine all stock looking so i have the turbo 400. Quote Link to comment Share on other sites More sharing options...
dbreese Posted March 26, 2016 Share Posted March 26, 2016 I have 3.73's with 28" tires, th350, and at 70 mph my autometer tach reads right at 3400. Could be a inefficient/ incorrect converter. Like Sam stated the factory tach could be well off. Hook up a temporary tach to confirm the rpm. David Quote Link to comment Share on other sites More sharing options...
FASTSS454 Posted March 27, 2016 Share Posted March 27, 2016 I had3.31 when I bought it then dropped 4.10's in when I raced it then changed to 3.73's when I put it back on th street and last summer I installed the S60 with 3.55, I like the 3.55 the best Quote Link to comment Share on other sites More sharing options...
Grapejuice1998 Posted March 29, 2016 Author Share Posted March 29, 2016 I have 3.73's with 28" tires, th350, and at 70 mph my autometer tach reads right at 3400. Could be a inefficient/ incorrect converter. Like Sam stated the factory tach could be well off. Hook up a temporary tach to confirm the rpm. David It sure sounds like 4k though! After talking with a fellow who owns a 69 Chevelle SS, he said his tachs about 3,800 @ 70 with 3.73's. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted March 29, 2016 Share Posted March 29, 2016 I have 3.73 and 27" tires, not over 3500 rpm at 70 Quote Link to comment Share on other sites More sharing options...
badddoin Posted March 29, 2016 Share Posted March 29, 2016 My 4.10 gears with a 27.75 in. tire turns about 3100 @60 mph. Quote Link to comment Share on other sites More sharing options...
502ci Posted March 29, 2016 Share Posted March 29, 2016 I can not remember what my 4.11 with a 28" tall tire turns at 70 but at 60 I think it is around 3200/3300 with a non lock up converter. I have a gearvendors overdrive on the back of my TH400 so it has been awhile since I turned it off to see what it would be. Quote Link to comment Share on other sites More sharing options...
Grapejuice1998 Posted March 30, 2016 Author Share Posted March 30, 2016 I can not remember what my 4.11 with a 28" tall tire turns at 70 but at 60 I think it is around 3200/3300 with a non lock up converter. I have a gearvendors overdrive on the back of my TH400 so it has been awhile since I turned it off to see what it would be. I would love to hear more about the GV o/d installation. Do you have a thread about it? Quote Link to comment Share on other sites More sharing options...
502ci Posted April 1, 2016 Share Posted April 1, 2016 My computer crashes in minutes of turning it on anymore...I had some links for you but lost them when it shut off on me just now. Do an advanced search typing in Gear Vendors and put 502ci in as the author and just hit search. A bunch of threads came up, you just got to scroll through them and look for my posts. I am using my cell phone right now and typing on it is brutal for me, lol. 1 Quote Link to comment Share on other sites More sharing options...
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