Differential strength comparisons

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clutchdust

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This thread is tailor made for Gary so I hope he stops in.
I'm curious to know what the reasonable limit (i.e. no dragstrip, mostly aggressive street driving) is for the various factory rear ends. The old c2/c3 d36 vs. the late c3 d44 (my current diff) vs. c4 d36 vs. c4 d44.
I know that most people really want the c4 d44 for most builds but the c4 d36 is fairly plentiful and cheap. I'm estimating less than 400hp at the wheels and would like the weight advantage of the c4 diff but currently have an iron c3 diff here at the house. Given my plans, the factory d44 in my car is probably the least conducive to what I want to do.
Also, from a strength standpoint, which is better? Higher numeric ratio or lower?
 
Higher numbers ratio will burn rubber easier, and that is the ultimate torque converter....after that....


GARY!!!!!!!


MIKE~~~~~~~~!!


:hissyfit::yahoo:
 
There is no c3 d36. 63 vettes had a dana diff that looks identical to the iron eaton and auburn externally. It's weak junk. All other cast irons are eaton or auburn. 80-82 are d44 ica, 84 had d36 and d44 hd

63 dana < auburn < c3 d44 < c4 d36 < eaton < c4 d44

Sent from my GT-I9000 using Tapatalk
 
Well actually,
63-64 and possibly some early 65 used an optional Dana posi as mentioned. The standard differential was an open cast iron case used up to 1970 when posi became standard. Most vettes were ordered/purchased with posi-traction.

The first design Dana's were not very strong at all but held up for the most part unless the cars were hammered and that was it. By the time the BB's were all over the place in the late 60's used vettes were cheap & plentiful, the majority of the Dana's were blown up. I still get in original 63-64 diff's with these posi's that survived 48 years of use but typically they were not abused during that run.

The 65-68 posi were Eaton, first design as I call them. For all I know they could be 100th rendition but it was the first Eaton used in the vette. It was better then the Dana and can be rebuilt today but they were very prone to cracking. Most of the ones I've got in were indeed cracked. If they are not cracked they should be correctly polished to extend the life of the unit.

The 69-79 Posi's were what I refer to as the 2nd design, again this is just my own terminology, like the term "Super 10 bolt" and "snow flake clutches". These posi's were indeed stronger then the previous 2 versions. They still will crack but not as bad compared to the others. The difference was in the casting.

The internal parts changed along the years as well. The 65-70 used solid steel clutches,the 71-79 used the snow flake garbage. The snow flakes were steel clutches cut out to allow posi additive in between them to "TRY" and resolve the clutch hammering issue common to these units. In abusive applications they simply broke apart as I have documented in the past. They did not solve the hammering problem which in fact was caused by production procedures, tolerances, and the added springs/plates. There is also debate on the function of a Eaton posi without those same plates and springs. I never use them in my builds and never had issue with hammering or posi action, as witnessed by the many that have my diff's in use to this day. The nye sayers are usually vette vendors who either don't know how to set them up or don't want to spend the time to tune them.

Auburn posi's were never installed from the factory in a vette but are sold in the after market as a less costly replacement. They are cone type, non rebuildable posi's that will not hold up as well as a tuned and polished Eaton will. Some have used Lockers but that is a rare custom installation most will not be able to do. Spools are also an option for drag cars, some do use them on the street but it's not recommended and they come in 12 bolt version which requires building a 12 bolt diff.

The spiders used from 65-70 were 10-18's which refers to the tooth count on the pinion and side gears.All spiders from '63-'79 were 17 spline. In 1971 they went to the stronger 10-17 spider which is the preference still today in either standard 17 spline or Tom's 30 spline count, heat treated or std.

The use of fiber coated steels came about a few years ago and are what is found in the new loaded Eatons and what some "vendors" try and push off on car owners as better parts,which they are not - in my opinion.

The 80-82 aluminum diff's used again a Dana posi, interestly they did not contain the springs and plates the Eatons use. The aluminum bearing caps were suspect and often a weak point on the left hand side and broke. The posi cross shaft had grooves in them and although some have run them without issue with 300-400-450 hp a lot broke with the stock engines of the time and some abuse. I don't care for the lot of them although I may start to rebuild them and fit a steel cap to them.

The c4 diff's I don't work on and although they are said to be strong they can not be built as strong as a custom Iron diff in the "super10" or 12 bolt conversion form.

The carrier(housing) was changed from 63-64, 65-67,67-79. Although pretty close in build the 67-79 carriers were better then the 63-66's. The pinion yokes are either a 1310 small joint size or the larger 1330 joint size. 1350 yokes are available and all are available in billet versions. The side yokes of the 63-72 were hardened more so then the 73-79's and I wonder if some of the later runs were hardened at all. They came in either standard or "heavy duty" form. The term HD here only relates to the retention of the joint caps, std yoke use u-bolts, the "HD" use strap and bolts. I believe there isn't much difference in strength here, I've seen the posi come apart before a u-bolt yoke broke. AS for the caps, the original yoke caps are the best and now run up to $150 a set where they were once $35 a set. The aftermarket has some and the ones I've seen are not fit correctly causing the cap to be too loose or bind from being too tight. They should be checked and fit just like a posi case bearing cap is.

Ring & pinion selection is limited to US Gear (Toms), Randy's Yukon, Richmond,and some Motive. I have used primarily US Gear but have also used Richmond and some Yukon. Not all of these are US made as well. Some have had a rep as noisey gears but the patterns I have seen from people with noisey gears were way off. Few realize the R&P used in the 12 bolt conversions are made by Richmond. I have a set in my son's street/strip 75 that do not make any noise at all.

So what to use? That's your call. I've stated my opinion for years on them, going with the way I build a blueprinted 10 bolt up to the 12 bolt conversion using Tom's parts. Anyone can buy the 10 &12 bolt kits from Tom but here's the current status: the 30 spline spiders are in short supply with an unknown replacement. These are the same spiders, heat treated or not, used in the Chevy 12 bolt applications. Once the current stock of Tom's is depleted the only option would be the new webbed powder metal spiders found in the loaded Eatons. Depending on who you talk to they could be considered fine or bad to use. I do not use them. Typically I see and read about "rebuilders" recommending and using the new loaded Eatons out the box as is and think it's great. To the rebuilder it is a faster cheaper way to charge a customer full price for posi then to take the time and build a stronger unit.To the customer they may think or be lead to believe that is the best option for them. I typically don't use new in the box common loaded posi's unless someone specifies it and that decision is based solely on money. A custom built one could cost almost double of a new loaded one but they can not compare.

Usually the rebuilders get offended by my comments because their potential customers will ask them about the differences between a new in the box and a custom one. Most will say a tuned posi is a waste of time and money or that the fiber clutches are better then anything else. I simply state my opinion based on what I've seen and used,not based on how many units I can sell in a given time.

There is about a 35 pound difference between an aluminum Dana and Iron Eaton diff. To me there is no reason I would consider that as an option given the vast superior way the irons can be built. This does not include the common catalog type builds, marketed with the cost effective owner in mind.
As with any type of build you can go average, pretty good, or the best with the results pretty much following suit.

Hope this helps you out, again just my opinion I'm sure others may disagree-not that it matters to me.
 
Last edited:
I would think that a larger gear would be marginally better at holding power.

What breaks gears and rear ends is shock loading. Nothing more, nothing less.

Since the gears in a diff are constantly in contact, the only way to do that is to plant down your foot on the gas and let go of the clutch or brake. Of course it also depends on the amount of rubber you have on your wheels. If you have small tires, you will just make them spin and the gears get less loading.
The bigger the tires are, the better your diff needs to be.

The same applies to the trans. However in a trans there is also another aspect to consider. Namely gear spread.
 
GTR1999 said:
So what to use? That's your call. I've stated my opinion for years on them, going with the way I build a blueprinted 10 bolt up to the 12 bolt conversion using Tom's parts. Anyone can buy the 10 &12 bolt kits from Tom but here's the current status: the 30 spline spiders are in short supply with an unknown replacement. These are the same spiders, heat treated or not, used in the Chevy 12 bolt applications. Once the current stock of Tom's is depleted the only option would be the new webbed powder metal spiders found in the loaded Eatons. .
Click to expand...

For some time, I was concerned that after Tom exhausted his stock of upgraded suspension parts, he might not reorder. These upgraded suspension parts are custom made and require a relatively large piece part count reorder. So to prevent not being able to buy the stuff I wanted, I ordered parts for a complete rear end upgrade from Tom. 1350's everywhere, 10 bolt, tuned diff, 30/31 spline driveline parts, billet yokes, new 3.08:1 US gears R/P, etc.

My original plan was to hold off buying these parts until he came out with his aluminum case. I've pretty much given up on that. I thought I better get these parts while the getting's good.

All the stuff I bought from Tom's is really beautiful to look at. I started out my order by talking to one of his young recent hired assistants. Because of the stuff I was ordering, I was soon talking to Tom. He remembered my name from his Bellflower, Ca location. There, Kenny had rebuild my 68 rear driveline.
 
Gave Tom another call Tuesday. Asked about the aluminum differential case. Tom once again didn't want to commit to a definate date. Apparently the machine company he's dealing with is still being reluctant to commit to large scale production. It'll be a CNN operation, and everything has to be exactly correct before machining a lot of CNN cases. I asked if his aluminum differential case cover would mate up to a stock iron differential case. He said it would, but because of a differential metals thermal issues, (aluminum to cast iron), he wasn't willing to recommend using it/or willing to sell it for use with a cast iron diff case.

I had ordered some 31 spline outer axles from him a few months ago, and they didn't come with his Kick Ass decals for the outer axles. I asked him if he would send me some. He said yes, for sure. Tom calls them "badges" not decals. He said they ship a lot of axles and then he said something about the cold weather, I didn't understand, but anyhow some are shipped without the "badges" because of the volume he ships. As for of axles being shipped, ......on the random day I called, Tom told me how many axles he was shipping that day, it was a large number!!! (Don't want to reveal the number). Even though the economy is bad, it seems that there's a lot of demand for Kick Ass axles from Toms.
 
"Someone" told me Tom was having trouble getting some 10 and 12 bolt parts. They "may" become a thing of the past.
 
A couple items:

I'm familiar with CNC machining. Is that what he said or meant?

My D36 has several thousand (road course) track miles on it, behind my turbo 355 six speed. No problems in this application. I don't drag race, so YMMV.

I would hope Tom's aluminum cover would work similarly well as the good results a lot of us have using the aluminum batwing on the older iron case units.
 
Come on guys, I made a mistake. I meant to type CNC but instead typed CNN. I think you knew that. Jeeze

I bought all the rear end stuff that I'll need for my 70 from Tom's about 4 months ago. I've been holding out buying this stuff waiting for the release of his aluminum diff case. But I got to be concerned that if his inventory of superior strength rear end parts was sold, he wouldn't replenish his inventory. My understanding is that he has ordered specialized parts production runs from OEM manufacturers (Eaton, etc) that meet his specifications; i.e stronger steels and 30/31 splines, etc. Once he runs out of these parts, he might be reluctant to order replacements, since he'd have to order large production runs to be sell parts at reasonable prices. The future market may not justify another large production run. So...I have no clue what Tom's inventory is, but if you're planning on buying some of his specialized parts, sooner may be better than later.
 
Geez...didn't mean to kill off the discussion. :(

At any rate, if you DO plan on keeping the Rube Goldberg IRS rear suspension, I would highly recommend you look into this modification:

http://www.dragvette.com/index.html

Even with the most beefed-up and super-duty rear end parts, if the IRS is doing it's "squat" thing, you aren't going to be putting all the power to the ground and you are risking all kinds of nasty and downright dangerous damage. This 6-link upgrade solves all those problems. It keep the tires planted FLAT to the pavement. And the four halfshaft loops pass NHRA requirements and keep the halfshafts from coming up through the floor in a catastrophic failure adn castrating you. That has to be a good thing :D
It works for both drag racing as well as autocross (whatever that is). It requires NO welding. It is a bolt-on installation.

Dep
 
GTR1999 said:
Well actually,
63-64 and possibly some early 65 used an optional Dana posi as mentioned. The standard differential was an open cast iron case used up to 1970 when posi became standard. Most vettes were ordered/purchased with posi-traction.

The first design Dana's were not very strong at all but held up for the most part unless the cars were hammered and that was it. By the time the BB's were all over the place in the late 60's used vettes were cheap & plentiful, the majority of the Dana's were blown up. I still get in original 63-64 diff's with these posi's that survived 48 years of use but typically they were not abused during that run.

The 65-68 posi were Eaton, first design as I call them. For all I know they could be 100th rendition but it was the first Eaton used in the vette. It was better then the Dana and can be rebuilt today but they were very prone to cracking. Most of the ones I've got in were indeed cracked. If they are not cracked they should be correctly polished to extend the life of the unit.

The 69-79 Posi's were what I refer to as the 2nd design, again this is just my own terminology, like the term "Super 10 bolt" and "snow flake clutches". These posi's were indeed stronger then the previous 2 versions. They still will crack but not as bad compared to the others. The difference was in the casting.

The internal parts changed along the years as well. The 65-70 used solid steel clutches,the 71-79 used the snow flake garbage. The snow flakes were steel clutches cut out to allow posi additive in between them to "TRY" and resolve the clutch hammering issue common to these units. In abusive applications they simply broke apart as I have documented in the past. They did not solve the hammering problem which in fact was caused by production procedures, tolerances, and the added springs/plates. There is also debate on the function of a Eaton posi without those same plates and springs. I never use them in my builds and never had issue with hammering or posi action, as witnessed by the many that have my diff's in use to this day. The nye sayers are usually vette vendors who either don't know how to set them up or don't want to spend the time to tune them.

Auburn posi's were never installed from the factory in a vette but are sold in the after market as a less costly replacement. They are cone type, non rebuildable posi's that will not hold up as well as a tuned and polished Eaton will. Some have used Lockers but that is a rare custom installation most will not be able to do. Spools are also an option for drag cars, some do use them on the street but it's not recommended and they come in 12 bolt version which requires building a 12 bolt diff.

The spiders used from 65-70 were 10-18's which refers to the tooth count on the pinion and side gears.All spiders from '63-'79 were 17 spline. In 1971 they went to the stronger 10-17 spider which is the preference still today in either standard 17 spline or Tom's 30 spline count, heat treated or std.

The use of fiber coated steels came about a few years ago and are what is found in the new loaded Eatons and what some "vendors" try and push off on car owners as better parts,which they are not - in my opinion.

The 80-82 aluminum diff's used again a Dana posi, interestly they did not contain the springs and plates the Eatons use. The aluminum bearing caps were suspect and often a weak point on the left hand side and broke. The posi cross shaft had grooves in them and although some have run them without issue with 300-400-450 hp a lot broke with the stock engines of the time and some abuse. I don't care for the lot of them although I may start to rebuild them and fit a steel cap to them.

The c4 diff's I don't work on and although they are said to be strong they can not be built as strong as a custom Iron diff in the "super10" or 12 bolt conversion form.

The carrier(housing) was changed from 63-64, 65-67,67-79. Although pretty close in build the 67-79 carriers were better then the 63-66's. The pinion yokes are either a 1310 small joint size or the larger 1330 joint size. 1350 yokes are available and all are available in billet versions. The side yokes of the 63-72 were hardened more so then the 73-79's and I wonder if some of the later runs were hardened at all. They came in either standard or "heavy duty" form. The term HD here only relates to the retention of the joint caps, std yoke use u-bolts, the "HD" use strap and bolts. I believe there isn't much difference in strength here, I've seen the posi come apart before a u-bolt yoke broke. AS for the caps, the original yoke caps are the best and now run up to $150 a set where they were once $35 a set. The aftermarket has some and the ones I've seen are not fit correctly causing the cap to be too loose or bind from being too tight. They should be checked and fit just like a posi case bearing cap is.

Ring & pinion selection is limited to US Gear (Toms), Randy's Yukon, Richmond,and some Motive. I have used primarily US Gear but have also used Richmond and some Yukon. Not all of these are US made as well. Some have had a rep as noisey gears but the patterns I have seen from people with noisey gears were way off. Few realize the R&P used in the 12 bolt conversions are made by Richmond. I have a set in my son's street/strip 75 that do not make any noise at all.

So what to use? That's your call. I've stated my opinion for years on them, going with the way I build a blueprinted 10 bolt up to the 12 bolt conversion using Tom's parts. Anyone can buy the 10 &12 bolt kits from Tom but here's the current status: the 30 spline spiders are in short supply with an unknown replacement. These are the same spiders, heat treated or not, used in the Chevy 12 bolt applications. Once the current stock of Tom's is depleted the only option would be the new webbed powder metal spiders found in the loaded Eatons. Depending on who you talk to they could be considered fine or bad to use. I do not use them. Typically I see and read about "rebuilders" recommending and using the new loaded Eatons out the box as is and think it's great. To the rebuilder it is a faster cheaper way to charge a customer full price for posi then to take the time and build a stronger unit.To the customer they may think or be lead to believe that is the best option for them. I typically don't use new in the box common loaded posi's unless someone specifies it and that decision is based solely on money. A custom built one could cost almost double of a new loaded one but they can not compare.

Usually the rebuilders get offended by my comments because their potential customers will ask them about the differences between a new in the box and a custom one. Most will say a tuned posi is a waste of time and money or that the fiber clutches are better then anything else. I simply state my opinion based on what I've seen and used,not based on how many units I can sell in a given time.

There is about a 35 pound difference between an aluminum Dana and Iron Eaton diff. To me there is no reason I would consider that as an option given the vast superior way the irons can be built. This does not include the common catalog type builds, marketed with the cost effective owner in mind.
As with any type of build you can go average, pretty good, or the best with the results pretty much following suit.

Hope this helps you out, again just my opinion I'm sure others may disagree-not that it matters to me.
Click to expand...

Interesting stuff. So are you a seller of complete rebuilt 3rd members? The reason I ask is the one I have in my car right now is a 3-series rear end (3.08 posi in 1972 Vette) and I want to install a 4.11 in it. I can get a rebuilt 4-series carrier, but all the Vette parts houses sell rebuilts like the ones you say are no good. I would hate to have to pay $1300 for a rebuilt and then have to send it to you to have it re-re-built to correct specs.
 
DJ Dep said:
Interesting stuff. So are you a seller of complete rebuilt 3rd members? The reason I ask is the one I have in my car right now is a 3-series rear end (3.08 posi in 1972 Vette) and I want to install a 4.11 in it. I can get a rebuilt 4-series carrier, but all the Vette parts houses sell rebuilts like the ones you say are no good. I would hate to have to pay $1300 for a rebuilt and then have to send it to you to have it re-re-built to correct specs.
Click to expand...

If you building a drag queen, I can see you 411 gearset and all the angst over it, but I don't know the specific ratio your 3 series carrier will go for....
maybe 373?? 355 anyway....

Kinda getting tough on these old cars, finding all the shit we had on hand in our pockets just a few decades ago....eh? :hissyfit::censored:
 
mrvette said:
DJ Dep said:
Interesting stuff. So are you a seller of complete rebuilt 3rd members? The reason I ask is the one I have in my car right now is a 3-series rear end (3.08 posi in 1972 Vette) and I want to install a 4.11 in it. I can get a rebuilt 4-series carrier, but all the Vette parts houses sell rebuilts like the ones you say are no good. I would hate to have to pay $1300 for a rebuilt and then have to send it to you to have it re-re-built to correct specs.
Click to expand...

If you building a drag queen, I can see you 411 gearset and all the angst over it, but I don't know the specific ratio your 3 series carrier will go for....
maybe 373?? 355 anyway....

Kinda getting tough on these old cars, finding all the shit we had on hand in our pockets just a few decades ago....eh? :hissyfit::censored:
Click to expand...

Gene: 3-series carriers won't take the 4-series gears. They will take any 3-series gear though. There is one place that sells 4.11 gears that fit a 3-series case, but that's kinda Mickey Mouse. :eek:
 
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