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Recommended gearing for 33's

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Blazin Ed

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Recommended gearing for 33\'s

I plan on getting my '88 K5 regeared pretty soon... I'm running 33's with a 4" lift. I believe I currently have 3.08's installed so it's pretty sluggish on take off. What would you guys recommend I regear to with my 33's. I'm planning on taking it Randy's Ring and Pinion since I live in Seattle... Any word on them?

Most of my driving would be 60% hwy, 40% city with occassional towing of a 18' boat, about 2500lbs.
 
Re: Recommended gearing for 33\'s

Go with 4.56's...you won't regret it. It'll tow very well and with the overdrive will do just fine on the freeway too. In town it should have plenty of snap too.

In my opinion GM made some major blunders with gearing in the 80's. No overdrive tranny equipped truck should have got anything less than 4.10's. The standard tire size was 31" and 4.10's would have been just fine...For 33's I think 4.56's would be perfect.

The extreme low rpm's you get with 3.08, 3.42's and even 3.73's and the 700R-4 lead to premature tranny failure and generally very poor acceleration. Deeper gears will help you almost everywhere. Acceleration, tranny life, towing, and most likely even mileage. A motor that's lugging doesn't give the best mileage.

For additional info, have a look around this forum and the Garage...the subject has been covered more times than I can remember and there are at least 3 other current posts about gearing.


Rene
 
Re: Recommended gearing for 33\'s

Rene summed it up very well i would recommend 4:56's as well /forums/images/graemlins/thumb.gif
 
Re: Recommended gearing for 33\'s

[ QUOTE ]
and even 3.73's and the 700R-4 lead to premature tranny failure and generally very poor acceleration.

[/ QUOTE ]

Rene, I've got to disagree with ya here. Ya probably read my other post on this subject. I never had tranny problems with my gearing and the accelaration was awesome. I wouldn't want to tow anything bigger than a small trailer with those gears and the hills could be rough, but the 3.73 won't wreck the tranny.
 
Re: Recommended gearing for 33\'s

I agree with Bubba Ray. I've got the 3.08s and my truck is just fine around town and the tranny is still like new(yes its the stock tranny) The only fault i can find is i can't smoke them as often as i would like, but we all know how to fix that problem. /forums/images/graemlins/grin.gif
 
Re: Recommended gearing for 33\'s

4.56's with 33's
4.88's with 35's
5.13's with 37's +
 
Re: Recommended gearing for 33\'s

thing is, everyone also says dont tow in OD. if you think about it, third gear would be 1:1 ratio, and you'd be spinning pretty high- a lot of the mph when I travel is 70mph speed limit.anyything less than 65mph and your gonna get rear ended. I tow 4000;bs with 33 and 3.73 in third gear, and in od if it is perfectly flat and not switiching around. 4.10 would be more ideal, and also pretty decent for 35" if you move up. but at that point, axle strength becomes an issue, so maybe worthwhile to get a different axle at that point.
 
Re: Recommended gearing for 33\'s

My neighbour's running a 396 in his '80 K20 with a Dodge (Getrag) OD trans. Tires are 285/75R16 (33?) and 3.73 ratio. He finds OD too tall... never uses it around town - strictly a highway gear.

Also consider the likelihood of upgrading to stronger axles, lockers, and the possibility of losing OD should you swap to a stronger trans/tcase, or even upgrading to dual t-cases. /forums/images/graemlins/thumb.gif

FWIW, I changed my daily-driver (Burb) from 4.10 to 3.21. Excellent swap for my situation. To each his own... everyone has different needs.
 
Re: Recommended gearing for 33\'s

33s and 4.56s you will be revving pretty high on the freeway. At 65 mph you will be reving about 2150 rpms, but thats with no slipage and a trus 33" tire. When I had 4.56s and 35" MTR (which measured 34") I would have to cruise down the freeway close to 2800 rpms to keep up with traffic. When I put 38.5s on my old burb with the 4.56s, it cruised down the freeway better. I would say if you do alot of freeway, nothing more than 4.10s. 4.56s are great for city driving though. Also remenber that you arent supose to tow in OD, so if you put 4.56s in it with 33s and in drive you will do 65 mph at 3100 rpms. 75 mph is over 3500 rpms /forums/images/graemlins/blush.gif
I towed my race boat with my burb on 35s (4.56 gears) in OD beacuse I couldnt keep up with traffic if I didnt, but I had a GM certa 700r4 and a built 350.

Dan /forums/images/graemlins/k5.gif
 
Re: Recommended gearing for 33\'s

[ QUOTE ]
I'm planning on taking it Randy's Ring and Pinion since I live in Seattle... Any word on them?


[/ QUOTE ]

Randy's is definitely one of the best in the business. You are luck to live near them. /forums/images/graemlins/thumb.gif
-Harrison
 
Re: Recommended gearing for 33\'s

Doing the same thing minus the boat towing and I'm moving from 3.08's to 3.73's, I think anything higher will run to high on the highway. I personally wouldn't go higher than 4.10 unless your running big tires (35+), I'm going to use 3.73 I think with the 700r4 it would work out better (I'm going with a LT285/75 -true 33" tire, 11.5" inch wide). Just my two cents though!

Ask the pros when you take it in! /forums/images/graemlins/thumb.gif
 
Re: Recommended gearing for 33\'s

I have said it time and time again. 3.73 is not enough gear for 33" tires.

Run 4.10s if you want to keep your 33s, 4.56 if you plan on at least going to 35s, and run 4.88s if you ever intend on going larger than 35s.

Too much gear isn't bad. Too little sucks.
 
Re: Recommended gearing for 33\'s

My opinion is 4.10 for 33's.
 
Re: Recommended gearing for 33\'s

Wow! Sounds like a lot of ya are leaning towards the 4.10's but there's also been some excellent reasoning on why the 4.56's are a good choice as well. If I only tow my boat a half-dozen times a year (less than 300mi) than the 4.10's might be a better all around choice for the 33's since I do a lot of freeway driving.

I'll also talk to the guys at Randy's and see what they recommend based on my vehicle use. I liked jjlaughner's quote "ask the pros"!! I'll let everyone know which way I went and how it turns out! /forums/images/graemlins/k5.gif

Thanks!
Ed
 
Re: Recommended gearing for 33\'s

If your going to change gears, minimum 4.10 or 4.56

Try the calculators on this page http://www.4lo.com/ and see what you get.
Im running 32's on mine with 3.73 and will go to 33's. IF I was going to 35's, I would go a minimum 4.56
 
Re: Recommended gearing for 33\'s

whats all this about not towing in overdrive? is that an old O/D trans thing? because gm says its ok to tow in OD with the new trucks...
 
Re: Recommended gearing for 33\'s

well when i had 33's and a turbo 400 i had 3.73's and np203 full time xfer.... NEVER and i mean NEVER had problems towing nor wheeling.... that is what low range is for if you need it......

but then i bought another truck.. rolling chassis with 4.56's and smc465 trans and np205 xfer.....
i actually got better gas mileage cuz i went from full time 4x4 to part time with locking hubs.... but went to lower gears.... i could pull down a house with the 4.56's and creeper gear.....

so if you have a daily driver and dont tow HEAVY HEAVY stuff i would say 3.73's... had no problem hitting 120mph with the truck with 3.73's

if you have a weekend warrior.... or expect to tow another heavy vehicle... i would go the 4.56's....4.56's down the highway ate more gas though..... but could only get the truck to 100mph......
 
Re: Recommended gearing for 33\'s

[ QUOTE ]
whats all this about not towing in overdrive? is that an old O/D trans thing? because gm says its ok to tow in OD with the new trucks...

[/ QUOTE ]

The new trucks have a "tow/haul" mode - a button you push somewhere on the dash or column (can't remember which). It probably turns off OD regardless of the shifter position... or it only enagages OD when its completely safe.
 
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