CELEBRATING 20 YEARS!

Next phase of my build http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=1069059&page=1 is going to be a rear end eventually on my way to a bigger engine. This is very early in the planning phase it will probably be January or February before I could even think about starting to purchase.

So, what's everyone's opinion on the different rearends? Im staying with a sbc, I think a good number for added protection would be able to at least handle around 600 h.p./ ft. Lbs but not really sure on that, just a guess. Once again early in the planning. I might take this car to auto x or drag strip no more than probably once a year and don't foresee any slicks, just a street car.

Pretty much 8.5s are hard to come by, then you have the s60 from strange, the moser 12 bolt, Ford 9", and I've read of some doing a 8.8 which is more involved but I would feel comfortable with the fab part if that is the end choice. You also have different vendors, I think i read in Lance's build thread that he used quick performance but had some seal issues at one time.

What is everyone's experience with different rearends and vendors? If you had it all over to do again which route would you go?

I will be watching this thread. I am hoping to do a rear end swap this winter, along with other work. Currently, I am leaning towards the Moser 12 Bolt.

Just to keep it as an option this is what Gordon (AkronAero) said in my build thread as far as what he went with.

"I'm running a 383 with AFRs and getting 535 HP / 490 FtLb at the flex plate and have a significantly upgraded 200-4R (Janis Transmission).
I discussed rear options for a one time upgrade with Henderson Driveline & Axle - like Janis they are very much used by serious/pros.
He put in a 3" DOM drive shaft w/ 1350 & 3R non-greaseable Spicer U-joints. They talked me down from 3.5" or aluminum.
I asked about 12 bolt or 9" but they strongly advised sticking with the 10 bolt case for cost and time.
Nice because they got parts in advance and I was able to drive in for the day and wait.
Put in a 3.73:1 Eaton - Detroit Truetrac and Moser 28 spline axles. New bearings and seals too.
Unless I am running super stickies on the track regularly, they say this is more than enough.
I'm not used to folks talking me out of spending money - So many good ideas on this site...?"

Brent, yes I forgot to include that I also put in a Moser rear differential cover (girdle) with main cap studs early on. (Add in a drive shaft loop). Cheap protection and easy. Glad to connect you with my driveline guy as you get closer if appropriate. He's in Cleveland OH but would answer your questions. Gave his son my stock posi to sell.....
Gordon

Fred, if I may ask what has you leaning towards the moser 12 bolt versus the other options?

Brent, I too have conversed with AkronAero concerning rear ends. Real nice guy. He too told me to just rebuild my 7.5 with 28 spline axles and Detroit Truetrac. Someday I hope to do a LS3/480 swap. I want this rear end work to be final and not have to work on it again. But Gordon is running 500+ HP through his upgraded 7.5 and it is holding up. So I have not ruled out his advice.

The reason why I am leaning towards the Moser 12 Bolt is that it appears to be complete and ready to install.. No sourcing E-brake cables or brake lines Also I read somewhere on their website that the housing comes already equipped with the little tabs to hold the brake lines to the housing. A fellow member bought one sometime ago and he posted his experience. He had a shop install it. The problem he reported is that there was no where to install the brake line T-Fitting that is bolted to the 7.5 rear. So the shop made a bracket that bolted to the frame somewhere. I think that issue will happen no matter which aftermarket rear you get.

I looked at the S60 for G-Body. A decent rear end. They are a little less costly than the Moser unit. But their housing does not have the tabs to secure the brake lines. I suppose it would not be hard to make the tabs yourself and weld them on.

A Ford 9 inch is overkill for my application. But Quick Performance is a tempting option.

Fred

I ran 12.4s and 1.55 second 60' times on 26" ET Streets in my old IROC (355 that made 331 RWHP or around 414 FWHP) through a TH350 and 3,000 stall on the 7.5” rear with stock 3.23 gears and Auburn limited slip differential with just an aluminum support cover installed. I beat on it pretty heavy, even running a number of off idle nitrous launches putting it deep in the 11s. It sure held up a lot better than the stock rear in the SS.

I destroyed the SS’s stock 7.5” rear end not long after an engine upgrade that put me around 480 FWHP. Rebuilt it with a 3.73 Richmond Gear (best at the time – supposedly better than the stock gears), Auburn HD unit, and 28 spline axles (don’t believe a brace rear cover was available then????). That held up for a couple months until the next power upgrade which put the engine around 540HP. The pinion gear broke in it just like the stock pinion gear. At that point, after much aggravation and what I now consider a colossal waste of time and money on the 7.5”, I broke down and put the 9” in the car. I consider the move to the 9" one of the best mods I ever made - once swapped I've never had another rear end related problem.

See, it’s not the 7.5” size of the carrier gear that’s the problem; it’s the pinion gear size, especially on the 3.73s. They are just too small to handle any kind of power; especially any “shocking” load/unload abuse. Here’s a comparison picture I found that gives a visual.



This was posted in the thread that contained that picture – “The pinion gear shears teeth due to case distortion. It's more common on the smaller pinions due to the smaller contact patch, which is typically used in setups that shock the driveline violently, causing the housing to move around. I've never seen a 2.73 or 3.23 gear-set fail, and that includes a few 9 second cars with 1.4x 60' times.”

Even with his comments, if you're planning on making any kind of power and plan to abuse it in any way, especially with a manual transmission, I personally wouldn’t put any money into the 7.5" rearend with 3.73 gears. However, if someone already has a 7.5” with positive traction, adding a LPW "Ultimate" cast rear cover (Strange has them with their own part number that may be cheaper) with the support girdle is pretty good and cheap insurance.



I like these covers better than the others because you can add an axle support brace (around $125 - plus minor welding for the axle housing tabs) to add even more insurance if you wanted (link to LPW - https://www.lpwracing.com/Axle_Tube_Brace_Kit/axle_housing_brace.html)

I am just finished up my rear end swap. I priced out updating the 7.5, sure would have saved a ton but then if it breaks?? Then back to square 1. Tried like Hell to find an 8.5 for over a year. No dice. So over last winter I built a Strange 9" center section with a Trutrac and Strange 3.89 gears, Daytona pinion support. Then a few months ago ordered their 9" housing and 31 Spline axles. Reall nice piece. For simplicity I did the 11" drum brakes. I have only put a few miles on it so far.

I am just finished up my rear end swap. I priced out updating the 7.5, sure would have saved a ton but then if it breaks?? Then back to square 1. Tried like Hell to find an 8.5 for over a year. No dice. So over last winter I built a Strange 9" center section with a Trutrac and Strange 3.89 gears, Daytona pinion support. Then a few months ago ordered their 9" housing and 31 Spline axles. Reall nice piece. For simplicity I did the 11" drum brakes. I have only put a few miles on it so far.

Maybe one of these days I can see how much power the 2.14 pinion can handle... Maybe I'll "upgrade" to a 2.73 since those shouldn't be easily breakable either


I've tentatively thought about the Explorer 8.8 as my upgrade path, mainly because I'm extremely cheap and those can be purchased with 31 spline axles, posi, and disc brakes for a couple hundred dollars, but the fabrication to put one in is quite a bit more. Southside Machine has a truss kit that seems like it has to be making some geometry compromises (I'd love to have that confirmed or denied if anyone knows), or a completely different suspension setup would be needed (I've got ideas on that but nothing that should derail this thread). There are folks running massive power through them, but I believe they are a little more efficient than a 9" or the other big dog options.

I'm really interested to see where this modification leads you, I've really enjoyed the engine and transmission journey.

Ford 8.8 with 31 spline axles, is my recommendation. 95% of the strength of most ford 9's with significantly less weight unless you spend big bucks and get an aluminum center section on the 9in. Trac Loks are cheap and rebuildable. GM has never really built a "good" passenger car rear axle.

Just like my 305 build I have to look at what I truly want out of my car and look at what I use my car for and budget. To be honest the most I do with my car is get it out and cruise around town on weekends and go to the local Friday night cruise in. I love the ride height on my car and I love how my car sits on the 245/45/17, 17x8 n90s and can't imagine getting away from them because its exactly what I wanted out of my car. If I get on it good leaving somewhere now the tires break loose so im pretty sure hooking will not be a problem. I think we need to be realistic that there is a 99% I'll never take it to a drag strip. All the local dragstrips are 1/8 mile and nothing but trouble any more, not my scene. At the most there might be a chance of autocrossing but who knows.

Everything above is an option all the way from the built 10 bolt to the 9". Im willing to bet that there is a good chance Gordon will never have a problem with his rearend because he knows what he will use it for. Some people need a 9". Me personally I feel like a 9" would be way overkill for me but its an option.

I've not even came up with a budget yet as I'm just looking at options now and getting opinions . The things I need to think about is what brakes will I go with and will I need to be worried about contact with the frame with the brakes. More than likely I will go with drums but that could change. I want to keep my aldan coilovers, they mount on a bracket that mounts to the lower shock mount on each side so that is another thing. Im staying with the wheels i have so no lug pattern change. Not sure on width yet more than likely stick with stock width but its to early to tell.. So what are some some of the foreseeable issues and challenges with these rearends and what will I need to make them work?

I want to thank everyone for for there input so far and know that it is valued. When I searched there were tons of these threads with rearend opinions but I wanted to start a new one just to see what everyone's latest thoughts are. So the list of possibilities is:

Strange s60
Ford 9"
Ford 8.8"
Built 7.65" 10 bolt
Moser 12 bolt
8.5" 10 bolt

I guess its time to slowly start weeding them out and doing research.

Perhaps all you need is to do nothing with the rear axle?

That is an option also but at the least a posi rear end. Once I go the 383, 400 route in the future I would hate to just see one tire mark.

Brent - I actually would have put in a Currie 9" (worked it out with Marcus/Mark Savitske at SC&C) but then realized I would also (convinced myself I would) "need" to do all new brakes (and some other changes) at that time and, well, it required too much bandwidth and more time than I have available. I agree with you that statistically speaking I will likely never have a problem, but if I do blow up the rear, well, so be it. That's just the universe telling me its time to finish it all. Unless of course MAP or others come up with an electric drive platform. Your ace in the hole is that you are more than technically competent and have the resources, plus the folks on this site with beaucoup knowledge and experience. Enjoying your threads - keep it up!


Also, per Kevin (BadSS) comments - Yes, general wisdom seems to be to change out the GM pinions (esp 3.73) for higher quality more durable brands.

Good Hunting
Gordon

Brent, I think you should cross the 8.5 off the list. They are hard to find now. I have seen some real crap 8.5's for sale on fleabay. I saw an add by someone who had an 8.5 with the upper control arm ears cut off. Had the cut ears with the rear and said they could easily be welded back on. Really???. Unless you are lucky to find one in decent shape, I would cross it off your list. If you are truly only cruising with the car, then building the 7.5 is a good option. It can probably handle some drag strip time. The S60, Ford 9" and 12 Bolt are all good rear ends. As you said, only you can decide on what you what out of the car and what you want to spent. I am in the same boat as you. Trying to make a choice. One of the previous posts about pinion diameter was interesting so I did some research in my books and on the web. I found the following results:

Pinion Stem Diameter
GM 7.5,10 Bolt: 1.438"
GM 8.5, 10 Bolt": 1.625"
GM 12 Bolt, 1.625 (8.875" Ring Gear)
Dana 60, 1.625" (9.750 Ring Gear)

I could not find info on the 9 inch. My books indicate that the S60 is more efficient than the Ford 9" and stronger. Maybe other members can comment.

Fred

I didn't know you didn't already have posi, so yes, that is a requirement...and you need to decide which axle spline to match it to (26 or 28).

2 interesting videos on the 8.8 going in a g body. First video is swapping the 8.8 to s10 disc brakes and correct bolt pattern axles. Second video is the full install of the 8.8 using the trick chassis setup. Looks to be a bolt on option other than welding on spring perches.

https://youtu.be/_Jqql4zOLlE
https://youtu.be/T3rFCqWxObU

Trick Chasis setup for the 8.8. It has all kinds of options.
https://www.trickchassis.com/product/8-8-swap-kit/

Another trick chasis kit with other options.
https://www.trickchassis.com/product/8-8-swap-kit-with-1-5-8-arb/

Just throwing options out right now and digging thru info. Fred I know that a good 8.5 is pretty much a needle a haystack. I did see a guy list one on a buick Facebook page that was built last night for $2200. In minutes it had 10 people wanting it. I just put it up there as an option. At a quick glance I will say that the moser 12 bolt would be around $3200-$3600 depending on brake options.

The strange s60 around $2500 not including brakes. https://www.strangeengineering.net/...ck-35-s-t-axles-coil-spring-mounts.html/

Here is what Strange says:
Street/Track: The S60 is equipped with a Spicer Trac-loc (clutch style) posi unit, Standard gear set, 35 spline Alloy axles, 7/16" or 1/2" wheel studs, HD 1350 series yoke, u-bolt kit and a steel rear cover. The Trac-lock is designed for street use in vehicles that will not be raced. The optional Truetrack (helical gear) differential is a great choice for Street/Track applications. Gear ratio choices are 3.54, 3.73, 4.10, 4.30, 4.56, 4.88, 5.13 & 5.38. Upgrades are available to the differential and wheel studs. Options include a chrome moly 1350 series yoke, Strange aluminum black powder coated cover, LPW HD aluminum cover and satin black powder coated housing. The steel cover would also be powder coated when this option is ordered.

My first thought was trying to keep the whole project under $3000, that was before I looked at prices and I was hoping to include brakes and driveshaft in that price. I still plan to keep on with this search to come up with real cost on each rear end option.

Added the info on the Ford 9" and 8.8" for comparison sake. However, it's not so much the pinion stem diameter as it is how it is supported, the size of the pinion gear head, and how much space is between the center of the head to where the teeth are cut.- that along with the thickness of the teeth. For instance, the 9" rear has the smallest stem diameter of those listed (great pinion support though), but it's probably safe to say there are many thousands of them out there handling over the 1,000HP mark without a hiccup (mine included on the spray with hundreds of track passes). That said, when I bought my 9" back in 1988, I didn't really do any comparison research and went with something that was readily available at that time and I knew would hold up (Currie bolt-in).

This link below is an awesome article with comparisons made between the Big Three (12-bolt, 9", and the S60) - including the RWHP differential (pun intended. ) Too bad they didn't make the comparison with a higher powered car or add a 10-bolt in the mix. I believe at that power level a built 7.5" 10-bolt would probably hold up.
https://www.motortrend.com/how-to/ccrp-0806-chevy-chevelle-rear-axle-swap/

Glad you brought up in this thread that you had an end goal of a built 383/400. Determining the final power level will help determine whether or not a built 7.5” will hold or if the money would be better spent on something beefier.

To put it in perspective, if you did nothing more than swap out your 305 short block for a 10.5:1 400 and go with a little bigger but still relatively mild cam, you could make upwards of 450HP running the same modified CCC intake and carb. Tons-of-fun torque (over 480lb/ft) and assuming a decent hook it could/should run a fairly easy 12.40-ish quarter mile, which is right there with a new Camaro SS and Ford GT.

A built 7.5, especially with 3.23 gears, could hold up to that power level with an automatic and probably the manual transmission as long as you were careful on the launches and refrained from all out power shifting – especially if you’re going to stick with 245/45/17 street tires and rarely if ever run a DOT drag radial. By the way, M&H makes a 245/45/17 DOT drag radial that would fit nicely and blend right in on another set of N90s.

With your fabrication skills, not having to pay for the additional work needed on them, then a Ford 8.8 looks like it might be a good cost effective option for you. From what little I’ve read here lately, it looks like most are saying the 8.8 and the 12-bolt are comparable in power limits, but I have no personal experience with either one.

The “problem” (if there is one) is, after talking with you a few times, I get the impression you may be a “fast is never fast enough” type - like most true hot-rodders. So, say you do just a 400 short-block next and want more later - if you top off the 400 short block with AFR220 heads, fairly aggressive HR cam, big dual plane with spacer, and something like a 850 annular discharge carb, you’re looking at 550-ish HP and 550-ish lb/ft torque.

If you think you’ll probably end up with a combination like that, if it were me, I would at least be looking at a S60. It or the 9” - cost would probably determine which for me. It might cost a good bit more up front, but doing it once and never having to worry about double working/double spending on a rearend would be worth it to me. I’ve been there, done that, and wouldn’t want to do it again!!

If you already had a posi in the stock rearend, then you might get away for a while (maybe longer if you’re careful) by putting on an Ultimate cover with the additional bracing. However, it’s more of a risk than just tearing it up and wasting money on it. When that last 7.5” pinion gear disengaged, I was braking in a turn-lane and just started turning into a parking lot. I was only doing about 30mph when it literally locked up the rear, bringing the car to a violent and near immediate stop. I couldn’t help but think what would have happened shifting into high gear during a race, or if it just let go on the highway during rush-hour traffic. So, whatever you go with, just make sure you build it to handle the power level.

So, first up is the option of building the 10 bolt 7.625 rearend. Positives are no driveshaft shortening, no figuring out anything on brakes, up front cost the way I would do it probably the cheapest. Negative is it won't withstand the power that the others will. But once again you need to be truly honest with yourself on what you plan to do and what type of power and traction you will use. The things that sucks about rearends is there is no given number they are good for. You can't say this rearend is good for this much h.p. and this one is good for this much. So here is the options for the 10 bolt 7.625.

If I were doing a new carrier I would go with the Eaton Truetrac, you have 2 options.

26 spline eaton Truetrac $478.23
Check out this page from Summit Racing https://www.summitracing.com/parts/dtl-911a319

28 spline Eaton Truetrac $489.50
Check out this page from Summit Racing https://www.summitracing.com/parts/dtl-912a317

If you went the route of the 28 spline for a little extra strength you would need new axles.

Moser 28 spline c clip axles 272.50
https://www.moserengineering.com/a1...tlass-grand-prix-malibu-monte-carlo.item

If you want rebuild everything including seals, bearings, and races there are several options.

Quick Performance rebuild kit with crush sleeve is $63, kit with solid pinion spacer is $78
https://www.quickperformance.com/GM-75-7625-10-Bolt-Master-Bearing--Install-Kit_p_21517.html

Strange install kit $94
https://www.strangeengineering.net/product/10-blt-7-5-complete-installation-kit.html/

Carrier shim kit $20, if needed

Support cover with main cap jacking bolts would help strengthen it some, if I was going with this option i would use this cover

LPW ultimate support cover $169
https://www.strangeengineering.net/...te-support-cover-accepts-brace-kit.html/

If a person wanted it also accepts a brace kit like Kevin posted above.
LPW brace kit $130
https://www.strangeengineering.net/...-fits-gm-12-bolt-86-04-mustang-8-8.html/

I've not checked the housing material, im assuming cast steel. If so I would tig weld the axle tubes to the housing with 309 or nickle rod. I would need to do some more reading on that.

Here is my cost estimate if I did the 10 bolt 7.5/7.625 on my car. Above are just other options for people to look at. Im not saying this is the route I would go but im going to put all options and cost on the table. While I still have my 305 I would just keep the gm 3.73:1 gear and driveshaft, if going this route i would upgrade both later on. I have 2 options.

Option 1

Eaton 26 spline Truetrac $478.23
Carrier shim kit $19.94
Carrier races and bearings $34.95
Lpw ultimate support cover $169
Fab my own brace kit materials $60
Weld axle tubes to housing
Gl-5 80w 90 gear oil $20
Main cap stud kit $30
Depending on shape of axle seals 86660s seals $14
Clean housing and paint $10
Ring gear bolts $40
While I had rearend apart I would check wear pattern and backlash to make sure everything is acceptable.
Total $876.12

Option 2
Everything same as above except
Eaton 28 spline Truetrac $489.50
Moser 28 spline axles $272.50
Total $1159.89

Next option is the 9" rear end. For comparison sake I'm going to compare most of these rear ends with 11" drum brakes. Also if I order a new rearend I will get it plain with no coating so I can weld on brackets if needed or any small modifications. One thing that worries me about the the QP 9" is it seems like there is quite a bit of problems with leaking seals and bearings not seating fully, If i remember correctly Lance had some issues.

Quick Performance 78-87 complete 9" rear end. $2015.00
New stock style big web housing center piece
Drain and fill plugs with jack pad $55.00
1/4" heavy walled axle tubes $30.00
3.70 gear
31 spline eaton Truetrac $125
Yukon Pro N case, Daytona Pinion Support, Billet Yoke $350
Total $2575

Not really sure i would need the Yukon Pro N case, Daytona Pinion Support, Billet Yoke, or the 1/4/ tubes but QP says its recommended for 450-650 h.p.

Currie 9" is another option and I can say up front that it is not in my budget, has all the bells and whistles but the price on it with the Eaton truetrac, no paint, and 11" drum brakes is $4138.

Strange 9" with truetrac, 11" brakes, no paint $3286. Pretty sure I figured that correctly but the site is a little confusing.

Next , would be figuring my cost to build one. Not sure it would be any cheaper. If I did I would just buy the housing with g body mounts. I do have access the pucks, bar, and collar for most rear ends to weld ends or shorten that I can borrow. A friend bought the Mitler kit to use on a few projects. Also no matter what rearend I buy it would be easier to slide thru a little at a time instead of one big chunk if you know what I mean but the downside is me being responsible for all the setup but I believe I would be fine.

Wilson, if you don't mind me asking did you keep track of cost for the whole project?

Brent, a good way to save on the center section is to find someone who has put a strange S60 or something similar into a 4th gen Camaro SS, they came with a 28 spline Torsen T-2 diff. Gear driven like the trutrac, but I got a whole discarded Camaro rear end for $80.

The 7.5 with the Torsen, a diff cover, and 28 spline axles held up just fine cruising, the occasional drag strip pass, and autocrossing.

Also the ford 8.8 is a great choice if you have a welder. Most explorer and mustang rears came with a posi, some explorers also had 4.10s.

I have a friend in 7's in the quarter mile on a 31 spline 8.8, the primary advantage of the 9 inch being able to change center sections quickly, the 8.8 is more efficient and lighter.