What all is needed to keep the same stock carrier and put in different gearing? i see talk about spacers, but don't know what that is. And whats the difficulty of doing this? thanks

Steve, you probably have a series 2 carrier, although it could be a 3 depending on what gears you have now. When you order new gears they need to know what carrier you are using to get the correct thickness gear. Some gear manufacter' make thicker gears so you don't need spacers. Find out which carrier you have and which gears you want then go from there.

If your fifth generation Elky has something smaller than a 2.73 then you should be buying for a 2 series carrier, I think anything 2.73 and up is considered a "3" series in 5th generation terms. But I could be wrong. Here is a good link to Richmond Gears for your 7.5" 10 Bolt 5th generation Elky.

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=1161&prmenbr=361

I used Richmond gears in my 5th gen (4.10:1) and just got my new set for the rear end I am working on upgrading to a 3.73:1. I like Richmond Gear and I also have their PowerTrax in the 80 I have.

I'd suggest the Richmond Installation Kit, the complete kit and you could also go for what they call the "Master" kit which includes the Rear Axel Bearings and seals. The complete kit has everything you'll need to rebuild the differential and replace all the bearings and shims.

When you remove the Carrier mark the caps for side and orentation before you remove them. They really need to go back just the way the came off. Its a good days worth of work by yourself.

I really would not recommend doing this unless you have had experience or have someone with you with experience. When I did mine, I had a friend that was a GM tech. He made it look easy but he know all the little tricks to set one up.

Tommy I've set up a few rear differentials and so I don't think it's too difficult. For a first timer experienced help is good but I think that anyone with a modicum of mechanical aptitude and common sense can do it. With a good workshop manual or one of those instructional videos it should be doable. Of course some special tools are needed and to buy these tools for one ring and pinion installation doesn't make sense.

I didn't use any special tools well other than a very large impact wrench. But Richmond Gear doesn't advocate in their instruction the need or use of any special tools.

Use the marking compound to determine the depth and "bite", use the shims to set the "mesh" or play. Crush the sleeve and away you go. Now the crush sleeve is a bitch but that is what the very large impact wrench was for. :D

I'd suggest that you also replace the U-Joints front and back while you have the drive shaft out.

Ok. I have never set up a 10 bolt 7.5" GM and I thought you needed a spanner wrench for the side bearings and a dial indicator/stand to set the backlash. Usually the marking compound is used to verify a good pattern.

Well you can use the Dial Indicator if you need it. I didn't use one. I think its the FORD 9" that takes the spanner to remove the side bearings. All the bearings in the differential are removed just like the ones in say the front rotor/hub. Knock out the race. Preload/depth can be set up with a dial indicator however once you've done several then you know what the feel is and what to look for. I don't use one. I just get it where I feel like the alignment is gold and use the marking compound to verify the pattern. If its not then I do a little more adjusting.

Actually that is not the hardest thing to do on a car and like most things after you've done it a few times you sort of know where to stop and when not to. Its nasty stinky but not that hard.

I think anything 2.73 and up is considered a "3" series in 5th generation terms. But I could be wrong.
In a 5th gen, 3.08 and numerically lower is a series 2. Anything numerically above a 3.08 is a series 3 carrier. There were no series 3 cariers that came stock in a 5th gen.

Here is a suggestion.

When you remove the pinion have the bearings pressed off the old pinion. Check the width of the spacer under the pinion. That is setting the depth of the pinion. It determines the place on the ring gear the pinion gears will mesh or depth.

What ever came out, thickness wise, put back in to start with. You probably will not have to add any additional shims there if you do this. If you don't it could become a pain really fast having the bearing pressed on and off until you get it right. The Pinion dimensions from shoulder to end is identical (or really, really close). Because this is a factory set up then you can or should feel comfortable with installing the same size shim under the pinion bearing.

Watch witch size spacers come from which side of the carrier when you pull it. Don't get in a hurry here. Remember that all the bolts on the carrier for the ring gear are left handed threads no right handed.

Get the Richmond Installation kit the master kit. Don't put the front seal in until you verify the pinion depth but it should be fine installing the same thickness as the old shim.

Put the spacers back where they came from (Side wise) on the carrier then check the gap/play. Adjust with the thin shims the left until the gears mesh as indicated in the instructions. Use the yellow marking compound to verify the gear pattern.

I just did this this past weekend. Its really a piece of cake if you do just what I did. The Spicer rear ends are all pretty much the same only no all GM rear ends were Spicer rear ends. Some of the BOP stuff was cheap somebody else and are weaker than the "generic" Chevrolet rear ends. (Buick Olds and Pontiac - BOP) I personally wouldn't use BOPs but some people do.

Oh yeah, I almost forgot. I always use the old crush washer/spacer also. At best you could have to crush it a little more but its either going to fit just right or it will be a little long and need to be crushed. This sure beats trying to crush the new one from jump street. Get a braker bar about 4' long to do the crush. You can't use an impact wrench. When you see the spacer you'll know why. I also had to use two additional shims that did not come with the kit behind the yoke with the new gears, but that is the first time that has happened to me.

Thanks Pete, it sounds as if you got ring and pinion replacements on a 10 bolt down pat. Do you use Richmond gear sets exclusively? Do you consider them the strongest? When 10 bolt, 7.5" rear axle asemblies fail because of high horsepower loads what breaks--bearings, ring gear, pinion gear. axles, carrier, spider gears, or axle housing? Is there any way to strenghten them witout extensive mods (i.e. $$$$$)?

I'd say that a good Spicer rebuilt 10 7.5 is capable of dealing with up to 400 horses or ~400Lb/ft of torque. I like Richmond Gears they are made here in the U.S. and Richmond seems to know all about rear ends.

My favorite 10 Bolt is the 8.5" 10 Corporate Rear End. This is by far, talking generic Chevrolet Rear Ends, the best one and is pretty close in strength to a 12 bolt 8.75". You can use it for up to about 450 Hp and 450/ Lb/Ft. of torque "rebuilt". Stock they'll do up to about 350 Lb/ft. of torque possibly up to 400.

Different things crake different situations. I would say that by far the most common failure is loosing a tooth or teeth. The carrier is pretty tough and with the gear bolted on it is good enough that I have never seen a carrier brake in a spicer rear end. Pinion and Ring Gears loose teeth, especially when they get old and worn. The metals and processes are way better than they were 10 years ago or even 5 years ago and certainty better than they were 20 years ago.

Lots of time when a tooth or teeth brake off then it locks up the rear end and rips apart the other stuff, twists the drive axels. If you want to look at something very weird, when you rebuild the rear end paint 3 white lines on both axels the length of the axel. After driving it and hot rodding it for 4 months remove the axels and look at the lines they look like a barber pole! The axels are suppose to twist if they didn't they'd brake right off the bat, shatter actually.

I like GM Parts in GM cars. I believe that a 12 bolt is faster on the track than the Ford 9" and I am pretty sure that can be backed by solid numbers. I'd advocate a GM 14 bolt 9 or even 10" rear over say a Dina 12". The differences is the amount of power consumed to make the gears start turning. Inertia.

Go as big as you can without sacrificing the jump. For a 5th generation Elky the 7.5" was a good choice by GM. The 305 didn't produce enough power even with FI to make a bit of difference where the rear end is concerned. With a 350 you start getting to the edge of its limits. So if you are planning over 400 Horses then plan on using a 8.5" Corporate 10 from a 73=77 model chevelle or Elky. It will need to be modified some to fit, but that will do you up to around 450 to 500 hp SBC unless you are running a standard. Then go to a 12 bolt ASAP. The 12 was designed when standards were the rule not the exceptions. 10s are great for automatics but can't handle the punch behind a standard clutch dump at 4000 RPM.

I am not an expert but I have some experience.

Thanks Pete for the info. I'm going to pick your brain a little more. The 10 bolt 8.5" from 1970s GM A bodies need what kind of mods to fit a 5th Gen? I know they are wider, are wheels with more backspacing adequate for fitment or do you have to narrow the axle housing? Are the locations/angles of the spring perches, shock mounts, and control arms different and what mods do they need? What about the driveshaft, yoke and brakes: bolt in, modify or replace?

Pull the bracketing from the 5th gen rear. You can use a larger offset on the wheels ro compensate for the 1/2" width differences.

So basically thats it just the spring supports, and the shock towers etc.. If I remember correctly its only 1/2" wider either by side or in total.

Check when installing the bracketing from the 5th to the new rear put the Pinion angle between 4 and 5 degrees from a level plane. Some I've seen do a Jig and some just take both rear ends side by side and cut from one install on the next. But the best Pinion angle is between 4 & 5 degrees. You can get the adjustable upper arms to do this without having to custom make a new set. GM sets the angls at about 2 degrees to about 2.5 degrees on a horizantal plane.

I forgot this: When a tooth or teeth brake off in the rear its generally a catastrophic failure. 8O

Do you mean cut off the brackets that attach the control arms from the 7.5" and transfer them to the 8.5", and also cut off the spring perch from the 7.5" and transfer it also. I assume that I will reuse the control arms from the 7.5". Do you know where I could get measurements and/or a jig because it seems to me if angles and distances aren't fairly close there will be binding during suspension travel. I can do the welding myself but I don't think I want to eyeball it. How about putting the 8.5' axle up in position with the brackets removed. Then cutting off the brackets from the 7.5" and attaching them to the control arms, I could set the pinion angle and then tack weld the brackets to the 8.5" housing. I could check the fit before making the final welds.

Yes

I don't know anyone that has an actual "Jig" that could be used. The few that we did, we did something that you were talking about. Take em both cut the brackets off the "Going To" and put it in front of or behind the "coming from" and take a few measurements to get them right. I would guess that you could slide the new under the truck with the control arms and bracketing attached set the angle then tack. I've never done it that way but it should work fine. I'd still take some measurements and mark it before I did that.

Sure the dimensions are important but not as critical as one would think if your off by 1/16" or less then you'll be fine. - as long as its not on the Pinion angle. 1/4" on the pinion angle will make a big difference you probably will not like at all. If your working NASCAR then its that critical.

Pete, you should check out the tech article in the new issue of Chevy High Performance magazine--it's called "7 1/2 Is Enough". It's an article about rebuilding the 10 bolt 7.5" for performance use. They claim that that a properly built 7.5" can handle 400hp at the rear tires (that's about 500 flywheel horsepower). They use new 28 spline axles, Moser 3.42 gear set, Auburn Limited-Slip differential and a TA aluminum cover with bearing cap preload, all for less than $1000.00. They give a very detailed rebuild instruction which is basically the same as the way you do it Pete. It kinda makes me wonder if I really need a 8.5", 12 bolt or Ford 9". Unfortunately they haven't posted the article on their web site yet.

ok kinda off yalls subject here but what would switching from a 2.73 to a 4.11 do to your gas milage, i know that it would hut it but how much off a loos are wwe talking here? anybody been here before? just wondering, with gas prices what they are i need to take these things into consideration.

Whatever fuel mileage you have would worsen. Also driving on the freeway would be uncomfortable as the engine would be reving much faster. For the street a 3.73 with a 1:1 high gear trans is about as high as you want to go.

You figure that with a 350 THM and a 2.73 @ 60 Mph your turning about 2100 RPM, with a 3.73:1 you'll be turning 24 to 2800 RPM at the same speed and with a 4.11:1 your RPM will be somewhere in the 3 grand range @ 60 Mph.

Your top end will come down from a Maximum possible of 160 Mph (With a 2.73:1) to around 90 Mph with a 4.11:1. The gas is that you'll get there so fast that its not funny or it is funny it will make you giggle like a little school girl. You wont believe the increase in takeoff torque even with something that is only producing around 300 Hp. (Flywheel)

If a 4.11:1 is your way and your set on using a THM 350 then forget the freeway completely. If you choose to slide in an overdrive then things get silly and really, really fun. Freeway speeds are once again possible and top end goes from around 90 to around 120 Mph. It will get loose at most stops and you'll be able to "goose it" in 3rd (going at about 40) and catch scratch. 1st and second would always be good for burning rubber (Talking smoking the tires not just a small scratch).

5.88:1 and the top falls out of the engine. 0-60 ETs will drop by at least 3s from a 3.73 with decent HP engine pushing it. top speed would be about 80 possibly but you'll be at 80 by the time you get into the 1/8th lights. Give up street and highway driving.

Going from a 2.73:1 to a 3.73:1 is like buying a brand new vehicle. The change is that big. It will amaze you how much power you will seem to have. Mileage will drop so if you like decent mileage then you'll have to suffer with 2.73:1 or get an overdrive transmission (T56 if you like standards) and you'd be able to slid into a 5.88:1 with the Viper version of the T56 and still have a comfortable 2200 RPM Cruise @ 60 Mph on the highway. Top speed would go back to around 130 to 150 depending on the build limit of your power plant. That is how they make those Dodge Vipers so stinking fast. Its all in the rear end and tranny.

If you think about a 10 cylinder engine that only produces 500 HP that is pretty cheesy. SBC can produce easy 500 ponies and still be very streetable, just not Gas Pump friendly and it will idle a bit radical.

In an El Camino 500 Hp is just too much. Try keeping her hind legs pinned with a 350 Hp power plant. Its almost impossible unless your running something in the 2s in the rear end then you get no stop light fun.

Just an opinion.

Thanks for the impressions on rear end ratios. A 160 mph El Camino, wow! You don't like Vipers do you Pete? Seriously though a rear end ratio of more than 3.73 doesn't make much sense on a street driven car without an overdrive trans. I have a '55 Chevy big block with about 650hp. I have a TH400 and have run gear sets from 3.92 thru 5.11 and have experienced the exhilaration of smoking the very big rear tires at any speed and in any gear, but the car is a Toy and not something I drive everyday. A lot of these questions about gear ratios come from young guys who use their El Camino as a daily driver. If they install real low gears the gas mileage and drivability go out the door. Believe me that driving down the freeway 55mph at 3500rpm + is no fun and gets tired real quick.

I went from a 2.73 to a 3.23 gear & my gas mileage suffered some.

Auto Math Handbook by John Lawlor is an excellent source of all kinds of formulas to figure out mileage, compression ratios, the effect of different tire sizes and how to correct your speedometer after you put in that highway unfriendly gear ratio. This book is easy and fun to use, even for the mathematically challenged/frustrated, like me. It is published by HPBooks and I found mine at my local Barnes & Noble, I've also seen it in the Summit catalog. This book is a worthy investment and takes a lot of guesswork out of anyones project.