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changing rear axel ratio

JeffnTanya

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JeffnTanya Enthusiast

JeffnTanya

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I was thinking of changing the rear axel ration from 3.08:1 to 3.73:1 on my '88 Silverado 350 TBI..  has anyone ever done this?  what is involved and where can the kit be bought?  the rear end is a limited slip.. does this matter when buying the gears?

StingRay Enthusiast

StingRay

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A buddy of mine swaped out his in a Suburban when his exploded.  Not an easy task for someone that has never done one before.  The ring and pinion sets go for about ?.  But when your changing the ring and pinion you should replace all the seals and bearings while its torn apart.  That will run another couple hundred.  Thats assuming that everything is in good shape.  Now when changing the ratio, the speedo has to be corrected too.  Thats just a gear inside the tranny.  You may want a shop to do this.  My buddy blew out that rearend again because of his faulty installation.

Frank S Senior Enthusiast

Frank S

Posted
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I'd definitely let a shop do this especially when it's not a full open differential.

If you don't get the tollerances set exact,you'll be throwing money out the window.

JeffnTanya Enthusiast

JeffnTanya

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I don't plan on doing this myself..  I'm just trying to find out how much this will cost as far as parts & labour.   the gear for the speedo can that be changed without removing the tranny?  isn't it an electo magnet or something?

Frank S Senior Enthusiast

Frank S

Posted
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iIf I'm not mistaken the speedometer gear is in the tail shaft of the transmission.

If you don't want to bother with that,your speedometer should be able to be recalibrated through the computer.

IMO,you will probably be happier with that modification than any other bolt on(other than a super charger) though it will probably cost ?-? but it will be one less thing to worry about if you plan to keep the truck.

GH6702 Enthusiast

GH6702

Posted
Posted
Quote: from JeffnTanya on 8:57 pm on Mar. 8, 2001

I was thinking of changing the rear axel ration from 3.08:1 to 3.73:1 on my '88 Silverado 350 TBI..  has anyone ever done this?  what is involved and where can the kit be bought?  the rear end is a limited slip.. does this matter when buying the gears?

 

Jeff,

Man I wish you were in Texas.  It looks like we have the same exact taste when it comes to trucks and performance.  I also have a 3.08 gear, but I have an open differential.  I'm pretty sure you do too, but I could be wrong.  This is what I was thinking about doing.  Just taking out the entire differential and swapping it with a 3.73 Limited Slip differential.  I have no idea how much it costs or where to get one, and I can't seem to get a straight answer from anybody.  When I go home over spring break, I'm gonna check with some of my motorhead buddies and some mechanics to see what's involved.  

Frank S Senior Enthusiast

Frank S

Posted
Posted

Any axle and drive shop should be able to set you up with the labor which is the more expensive of the two.

Ypu should be able to find a real good ring and pinion set for under ? but you'd be wise to go ahead and have everything inspected/replaced while you're at it.

NeXuS1 Enthusiast

NeXuS1

Posted
Posted

what about your 4wd? if you changed the gearing in the rear end wouldnt it kind of throw that off? or does it not work that way ?

NeXuS1 Enthusiast

NeXuS1

Posted
Posted

cuz i want to change my gearing.. its stock with bigger tires.. (bad) and its just killing me.. so i've assumed you'd have to do front and rear, which seems like it would cost a lot.. but would it help with milage?

also would would be suggested for my truck running 35s ?

StingRay Enthusiast

StingRay

Posted
Posted

Hey YZr2k,

Its not my truck were talkin about(I allready have 3.73 and a G80), its JeffnTanyas truck.  If I am not mistaken, He has a 2WD.  If I remember correctly you could not get 3.08 in a 4WD in '88 up full size truck.  3.42 was the highest ratio.

JohnGMC Enthusiast

JohnGMC

Posted
Posted

Ring and pinion +installation kit will run 350-400 at the most,the loabor will run at least the same,anyou can ge the burner for the new ratio for 30 bucks,you gotta remove the dash and burn in the new info into the dashboard itself,not hard,but time consuming.the 3.73's will wake up that truck ,big time.You might be able to find a rear in a wrecking yard for about 500 and put it in yourself,and sell yours if its good-for 300 or so,you'll save money too,but dont tknow how hard the rear was abused.

JeffnTanya Enthusiast

JeffnTanya

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I was doing some computer work at the local chev. dealer today.  I talked to the tranny guy about this and he said no problem he could change it over and he would replace the bearings and clutches if needed at the same time..  then I talk to another mechanic which I usually talk to about my problems and he said not to do it as the engine will rev. high all the time and that at 5000rpm power drops off.  he said I would loose a lot of top end.  he also said something about cutting resistors in behind the dash and a prom upgrade..  anyone have an opinions on this??  I would hate to do it and not be pleased with the output.

Frank S Senior Enthusiast

Frank S

Posted
Posted
Quote: from StingRay on 12:33 pm on Mar. 9, 2001

Hey YZr2k,

Its not my truck were talkin about(I allready have 3.73 and a G80), its JeffnTanyas truck.  If I am not mistaken, He has a 2WD.  If I remember correctly you could not get 3.08 in a 4WD in '88 up full size truck.  3.42 was the highest ratio.

 

I know but I beleive that NeXuS was referring to your truck or maybe it was his own so I decided to drop that in as well.

HiG4s Enthusiast

HiG4s

Posted
Posted
Quote: from JeffnTanya on 9:51 pm on Mar. 8, 2001

I don't plan on doing this myself..  I'm just trying to find out how much this will cost as far as parts & labour.   the gear for the speedo can that be changed without removing the tranny?  isn't it an electo magnet or something?

The newer GMs the speedo is adjusted with a computer not changing the gear. Not sure just what year that started.

If you look around you should be able to find a shop that will install rear end gears for about ?, not sure what the price of the gears will be. See if you can find a local Camaro racing club, these guys are always changing rear gears and should know  the cheapest reliable place around.

 

(Edited by HiG4s at 9:32 pm on Mar. 9, 2001)

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