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Differential and Transmission upgrade

7K views 84 replies 20 participants last post by  jelco 
#1 · (Edited)
I have a 64 El Camino 283 engine, power glide transmission, with what I believe is the original 10 bolt 8” rear end and I believe it has a 2.56 gear ratio, GM1, #3839390N.

I’m thinking of upgrading to 3.42 or 3.54 gear ratio and upgrading to a 700 or 200-4R transmission in the near future. The plan is to make it a daily driver on street/highway and drop in an LS1 engine at a later date.
I have 17 inch wheels, 245-45-17 I believe.

I’m a noob but I plan to upgrade the gears myself. What’s a good upgrade kit?
Would this combination be ok for now with the 283?
Would the jump from 2.56 to 3.54 be hard on the 283 with power glide?
I’ve read the 200-4R is an easier install then the 700R4.
Any corrections, suggestions or advice?
 
#2 ·
Your '64 will have the 8.2 10 bolt. The gear ratios for that rear end would be 3.36 or 3.55. Swapping gears is not an easy job for a beginner. You need a few special tools and you need to be able to set the pinion depth, bearing preload and backlash to get the correct contact pattern. The '64 8.2 had slightly different splines on the axles than the later years, so when you swap the differential for a 3 series you will also need to upgrade the axles. You will have to swap the differential for this gear swap because you currently have a 2 series and you need a 3 series for the gear ratios that you are considering.
 
#3 ·
Thanks for the reply. The previous owner installed a 1979 Buick regal rear end to allow his wheels to fit. I may be doing things backwards but I think there's a little play in the gears and want the wider wheel base, since its off the car I figured I'd give it a shot. I'm a noob but I'll have a little help (hopefully).

I agree about the 2 (2.73 and 3.08 gearsets) and 3 (3.23 and 3.42 gearsets) series from the factory but I've also read if a 2 series carrier is used, a 'thick' ring gear set can be used for 3.42,3.73,or 4.10.
Is that not right?

I'll double check on the numbers and send a pic. I think 3.36 or 3.55 gear ratios would be fine for daily driving but would you recommend 3 series 3.42 gear ratio?
Any idea what kit would be good to purchase?
What Axles?
 
#4 ·
If you have a 7.5 rear end from a '79 Regal then you need to get that out of the car now and put something in it that can handle a little power. That little rear end will not handle what you are building. Don't invest one dime in that rear end. Find a good 8.2 core from a '65 or '66 Chevelle and use that, or find a 12 bolt if you can.

You will have as much help as you need here.
 
#5 ·
Where are you located? I'll be pulling out the stock 8.2 10 bolt from my '64 wagon in the next few weeks. I'll let you have it for a case of good beer. :D
 
#6 ·
That's kind of you but I have an 8.2" 10 bolt already that I'm thinking about rebuilding. What are you replacing it with? I'm in San Diego.
I was told Astro Van's have an 8.8" rearend but I'm not sure about the wheel base difference. Anybody do an astro van swap?
 
#8 ·
I found a 4:10 12 bolt posi from a '65 in Phoenix about a year after I bought my wagon. The owner had it on CL for $1200, so I jumped in my truck the second I saw it listed. Paid $1000 for it. Needless to say, I was pretty happy that afternoon.
 
#7 ·
You need a '64 to '67 A body rear end. No other rear ends have the correct suspension geometry to work correctly in your car. You can install a G body rear end with special modified control arms and cutting and welding, but then you have a piece of crap 7.5 rear end that will not handle any power. My advice is keep it simple and use a rear end that will fit your car correctly.

The Astro van had the same 7.5 rear end as the G body. I wouldn't even consider it.
 
#14 ·
How does ‘big gear head’ know my GM1 rear end originally came with a 3.36 or 3.55 gear ratio?
Searching online showed “GM1” stamper rear end is 2.56.
What is a good 10 bolt 8.2” kit to purchase for a daily driver?
I’ve watched several YouTube videos but if anyone knows of a good one that is more specific to my car, please don’t hesitate.
 
#17 ·
Freddie, aka Big Gear Head, is our resident expert on rear ends. He was simply letting you know that 3.36 & 3.55 gears are your choices when it comes to 8.2 10 bolts if you wanted to lose your 2.56 gears

3.23 & 3.42 are ratios for GM 8.5 10 bolts. Neither will work for your application.
 
#16 ·
I wasn't clear on that. You listed 3.42 and 3.54 as gear ratio options for your rear end. Those gear ratios are not available for the 8.2 10 bolt, which is what I assumed you had because that is what would have been in that car. The correct gear ratios in that range for that rear end would be 3.36 and 3.55.
 
#18 ·
Ok thanks for the clarification. So get 3.36 or 3.55 3 series and replace the axles?

Several sites indicate a "GM1" has a 2.59 gear ratio (I mistyped 2.56 earlier), I haven't determined by counting the ring and pinion gears if it has been left that way over the past 55 years.

Do I have y'all's blessing to go ahead with 3.36 or 3.55 gear ratio if I leave the engine and tranny stock for a few months then switch to 200-4R or 700R4 and a salvaged LS1 down the road?
 
#20 ·
Do I have y'all's blessing to go ahead with 3.36 or 3.55 gear ratio if I leave the engine and tranny stock for a few months then switch to 200-4R or 700R4 and a salvaged LS1 down the road?
If you are going to an overdrive transmission, do yourself a favor and go with the 3.55’s. With a low horse engine and low cruise rpm the car could be a little balky with the other gear.
 
#24 ·
I have the 700 (did the swap about 20 years ago) and it holds up great. That said, buy a built 200 and you will be way happier. Nobody was building the 200's when I did the swap, so I had to shorten the driveshaft and modify the crossmember. You don't have to do nearly as much to use a 200, as it is the same length as your old transmission. Another advantage of the 200 is the gap between first and second gears is not huge. the 700 has a 3.06 1st gear and 1.62 2nd gear, and the 200 has a 2.74 1st and 1.57 2nd.

Shifting from 1st to 2nd at 5,000 rpm, the 700 will drop to about 2,600 rpm and the 200 to 2,900. I definitely feel the bog when the car shifts from 1st to 2nd.

I also have a (non-posi) 12 bolt with 2.73 gears and it is a highway monster. 2,000 rpm at about 80 mph. I think low to mid 3 series gears would be perfect.
 
#26 ·
Here is my 2 cents
if there is a Rearend in the car now drive it like it is for now as a DAILY driver

Then get all the right parts to swich over assembled
eg.
1. the right 12 Bolt Posi with the Gear Ratio to fit/match up to the new Engine / Trany / you are going use
2. get the 3/4 speed Trany you can afford with the lest amount of work needed to install it into your car
..... TH400 if you also want to do some fast fun time at the Track & Cruzin that is almost Bullet Proof with a 3.08 to 3.31 Gear Ratios in the 12 Bolt
..... 2004R for a Daily Driver & Cruzer with 3.55 or 3.73 Gear Ratios in the 12 Bolt
..... 4L80 for a Daily Driver & Cruzer with 3.55 or 3.73 Gear Ratios in the 12 Bolt
3. the Engine you want with it ready to go
..... LS SBC for good Gas Mileage and plenty of HP
4. a new Shifter to make sure the Trany will shift great
..... I just put a B&M Pro Ratchet in my 67 and I love how it shifts my Newly Rebuilt TH400 with a Reverse VB
5. a new correct lenght HD Driveshaft with 1350 Ujoints
 
#27 ·
Yeah, probably wise to wait to upgrade the rear end until I have the tranny and engine to upgrade with it. I'm going to try to find a decent salvage yard LS motor at some point then buy a rebuilt 200 or 7004R transmission. If I'm not racing I'm thinking I can stick with the 10 bolt 8.2" for a while before upgrading to the 12 bolt 8.875".
 
#31 ·
Using a 7004R for Racing would be a Rebuild of it every year and the possiblity it will break at the Track IMHO

Yes parts are easier to come by because they are always breaking down and need Rebuilding more often

I Race my car with a TH400 in it, just had it Rebuilt this year to install a Reverse VB and Higher Stall Converter

The last time I had the TH400 in the Trany Shop was in 2009
10 years of Cruzin the Hwy/City Streets and weekends at the Track

If I wanted a 4 speed for Cruzin and Track Time it would be a 4L80M
If I wanted a 4 speed just for Cruzin it would be a TH200R4
 
#30 ·
Since you are in southern CA you could always go to bowtie overdrives for your 2004r. I think there are other shops down there as well. Be wise and have them build and install it. That way they own any issues. The 2004R can be finicky to get everything right. I think Bowtie has one of the best TV setups out there. Having said that, if I was planning an LS swap, I would also swap in a more modern transmission at the same time and forget about the 2004r or 700r4.
 
#34 ·
Its an old rear end,it could be old casting flash or something from when some work was done you don't know the history of the rear could be anything.Take a strong flashlight and look the gears over carefully I doubt you'll find anything broken but it's always good to check.
Also you don't have to count the teeth if you find these stamped in numbers on the side of the ring gear.
Mine was stamped 43-13 that makes it a 3.31 you should find numbers similar but not the exact same numbers, like them on the outside of your rear end ring gear. So while you're checking for any damage you can look for the ratio stamping on the outside of the ring gear.
 
#35 ·
That's a question with many answers. Stock housing? Used or rebuilt? Bare or drum to drum? Early 65-67 or late 68-72? Open or posi? Desirable street gears from 3.42 to 4:10 or race gears from 4.88 to 5.38?
 
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