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ANOTHER gearing question!

4

454 blazer

1/2 ton status
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Feb 27, 2008
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bahrain
Hi guys,
im running a 468 big block th350np205,on 33,s , the thing is its really sluggish of the lights , once it hits around 2000rpm it flys, ive also noticed that when im cruising just getting into 3rd gear it seems to want go back into 2nd then 3rd then 2nd if that makes any sense :confused: would changing the gears help ? i do some duneing from time to time , but mainly street. 4:10s ? or 4:56 ? :eek1: , its also not a daily driver. Any advice from you legends would be appriciated:bow:
 
Go with the 4.56 and be done with it. Assuming you have a ratio in the 3's...4.56 will be a night and day difference.
 
with an auto 3 speed id go 4.56 if you only have 33 inch tires.that should be good up to 35s and still give you a good highway rpm if you decide to step up a size later.
 
all the 12 bolts i had were 3.73.i went to 4.10 when i got my 3/4 ron rear.4.56 in a auto would be night and day compared to 3.73 gears.im surprised with a big block it picks up slow with your setup.my 350 is scary fast if i get on it hard.i got a manual tranny also though so i can hold it at 100 percent lockup without slippage.you sure your tranny aint slippin if it doesnt go good til 2000+ rpm?maybe the engine has more components for hp and not torque til a higher rpm.i built mine for better low end torque and didnt worry about high rpm hp.just a few thoughts.
 
The 10bolts in my '89 K5 have 3.42s in them, not overly impressed with that lol
 
I'd pull the cover off your diff and see exactly what gears you currently have. i had an 81 jimmy that had a 12 bolt...2.73's. 3.08's were also very common in the 12 bolt.

With 33's and a TH350 I would not go with 4.56's, unless you like freeway rpm's at 3200 rpm. 4.10's are a bit better, 2850 rpm @ 65 mph. 3.73's would be ideal (2600 rpm @ 65).

My guess is you have 2.73's, it's about the only ratio that could make a 468 feel sluggish off the line.

Rene
 
chulisohombre said:
all the 12 bolts i had were 3.73.i went to 4.10 when i got my 3/4 ron rear.4.56 in a auto would be night and day compared to 3.73 gears.im surprised with a big block it picks up slow with your setup.my 350 is scary fast if i get on it hard.i got a manual tranny also though so i can hold it at 100 percent lockup without slippage.you sure your tranny aint slippin if it doesnt go good til 2000+ rpm?maybe the engine has more components for hp and not torque til a higher rpm.i built mine for better low end torque and didnt worry about high rpm hp.just a few thoughts.
Click to expand...

Yes,i think looking at my specs its a hp motor , rectangle port heads , comp 268 4x4 extreme energy cam , holley 750 double pump , custom made hooker headers (long) , i used to run a 2,500 stall converter , it used to fire up the tyres big time at the lights , but it was a pain in the butt around town , so i put a stock one in,im liking the idea of the 4:56s it doesnt do much highway driving , i dont think this is a good idea but as an experiment i put it in 4l and (with hubs free) and the take off although short REALLY opened my eyes LOL! Thanks all you guys for the great feed back ...I love this site !
 
I think you have other problems. You can run any gear with a 454, yet a 468, and not be sluggish off the line. I've had a lot of trucks with big blocks, some way over tire'd and undergeared, and still wasn't a slug off the line.

Then again, what do you consider sluggish?? Is your other ride a Camaro or Vette?? Then this would feel sluggish....
 
Its your stall converter. First thing I thought when you said "468 and sluggish". 3.73s should be plenty with that motor and 33s.
 
if it dont run on the highway much,i would put in 4.56.if on highway alot i dont do much over 60 on my 4.10 gearing.with the 35s im running around 2700 rpm witch is a good cruising speed.but at 8 mpg,i dont go real far for very long on the highway anyway.lol.im sure with the big block you are about the same.i would check and see what gears you have before you change them.as it could be different then 3.73.i really like my 4.10 and if you plan on staying with 33 inch tires that could be a good ratio for you also depending on what you currently have.if you have 2.73 or 3.08 gearing 4.10 would give you alot more torque to get the engine in a better range.even 3200 on a big block aint that bad if you go 4.56 gearing.4 low with mine and im 3000 rpm at 5 mph.its a big difference form 4 high.plus i got the granny low 6 to 1.so that helps also for crawl ratio. yours is 3.? to 1 first gear i believe in the tubo 350.going to 4.56 from 2.73 would be like driving in 4 low now all the time.may not be ideal but will get a better snap neck feel when you get on the skinny pedal lol.
 
Check what gears you actually have before you make ANY decisions.

Martin
 
I think you either have other problems, or your perspective of "sluggish" is different than most. Is the engine tuned correctly (both ignition and carb)? Is it built as a "high-revver"? If you indeed have 3.73 gears that should be plenty with a built big-block and only 33" tires. 4.56 is a LOT of gear for 33's and a non-overdrive transmission.

2.73 or 3.08 gears could cause some issues, but I would think you could still light up 33" tires at will.

Regarding using low range, keep in mind that's multiplying the gear by almost 2:1. Even with 3.08 gears it would feel the same as having axle gears in the 6:1 range.......point being that even dropping down to 4.56 gears wouldn't even put you close the same feeling.
 
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