My turboV8 Regal finally has some rear. Since, like all non turbo regals, it was disgraced at the factory with a 7.5 10bolt and then even worse an olds engine I felt she needed some dignity back. I equipped her with an 8.8 rear end from a SN95 stang. That way the Ford guys have something familiar to look at when they are behind me at the strip. Well, other than buick taillights that is. See the whole buildup with pics at the link below. Feel free to post questions and feedback as both are appreciated. Chris
My Regal 8.8 swap is complete
- Thread starter topher455
- Start date
They are 5x4.5 in the rear 5.5bs 285 40 17 (the 8.8 is 60.5 vs 58.5 for the 7.5) and the rear end literally bolted in. I just had to weld my old spring perches to the housing and hook up the brakes. Also it looks like I could widen the wheels 1in (6.5 bs)and run bigger tires without a problem.
Brer Rabbit
Pursuit Specialist
- Joined
- Feb 5, 2005
very nice,
What was the total cost?
What was the total cost?
Hi Topher,
Some questions/observations:
1.) Is the 8.8" Ford rear stronger than the 8.5" GM rear? And if so, how is that known?
2.) You mention that the rear was a bolt-in swap, but you seem to have CA's with spherical races. The UCA's for example, don't form a 90-degree included angle as they do in the GM configuration, but (eyeballing your pictures,) maybe only 60 degrees (which reduces lateral stiffness location for the rear, incidentally.) There are similar uncertainties about the LCA's. In short, if someone has OEM bushings or simply bushings without spherical races, this doesn't look like a bolt-in swap. Also, the suspension geometry is changed in ways which may or may not improve handling - for example, what about pinion angle, rear roll center height, and anti-squat behavior?
3.) Related to (2.,) how is the fore-aft position of the rear relative to the chassis changed? (I supect it gets displaced aft.)
4.) What is the compatibility of the Ford disc brakes with the GM brake system?
5.) You already mentioned the incompatibility of the bolt circle pattern between Ford and GM.
6.) You already mentioned the difference in width between the two rears.
7.) How does the weight of this rear compare with the 8.5" GM, aside from the brakes proper? This Ford unit looks heavier.
8.) What is the vertical pinion offset of this rear relative to the 8.5" GM unit?
9.) What is the lateral pinion offset of this rear relative to the 8.5" GM unit? Or better, where does the lateral location of the center of the pinion yoke U-joint fall upon installing this unit into the car, relative to the GM rear?
The conclusion I get is that this is hardly a bolt-in swap (although not trying to knock your efforts by any means, Topher! It looks like you did a great job.) On the face of things, this seems like a lot of trouble to go through for an improvement in strength, presumably. Speaking for myself, this difference would have to be very large to merit correcting all of the other differences between the two rears.
Best,
MAP
Some questions/observations:
1.) Is the 8.8" Ford rear stronger than the 8.5" GM rear? And if so, how is that known?
2.) You mention that the rear was a bolt-in swap, but you seem to have CA's with spherical races. The UCA's for example, don't form a 90-degree included angle as they do in the GM configuration, but (eyeballing your pictures,) maybe only 60 degrees (which reduces lateral stiffness location for the rear, incidentally.) There are similar uncertainties about the LCA's. In short, if someone has OEM bushings or simply bushings without spherical races, this doesn't look like a bolt-in swap. Also, the suspension geometry is changed in ways which may or may not improve handling - for example, what about pinion angle, rear roll center height, and anti-squat behavior?
3.) Related to (2.,) how is the fore-aft position of the rear relative to the chassis changed? (I supect it gets displaced aft.)
4.) What is the compatibility of the Ford disc brakes with the GM brake system?
5.) You already mentioned the incompatibility of the bolt circle pattern between Ford and GM.
6.) You already mentioned the difference in width between the two rears.
7.) How does the weight of this rear compare with the 8.5" GM, aside from the brakes proper? This Ford unit looks heavier.
8.) What is the vertical pinion offset of this rear relative to the 8.5" GM unit?
9.) What is the lateral pinion offset of this rear relative to the 8.5" GM unit? Or better, where does the lateral location of the center of the pinion yoke U-joint fall upon installing this unit into the car, relative to the GM rear?
The conclusion I get is that this is hardly a bolt-in swap (although not trying to knock your efforts by any means, Topher! It looks like you did a great job.) On the face of things, this seems like a lot of trouble to go through for an improvement in strength, presumably. Speaking for myself, this difference would have to be very large to merit correcting all of the other differences between the two rears.
Best,
MAP
Wow thats alot of questions. I will try to answer them all.
1) car originally had a 7.5 as it was not a turbo car
2) the 8.8 has been deep into the nines in 3-3300 lb mustangs
3) a good 8.5 costs between 750-900 same for a 12 bolt
4) 8.8 has same size ring gear and pinion as a 12 bolt
5) I hate seeing turbo cars cannibalized for their rear ends there scarce already
6) The arms are from TRZ motorsports and are the same double adjustable arms as they sell for g bodys
7) the lca attaching points an the rear are 1" wider per side creating an angle less than 90deg which will triangulate the rear suspension (increasing strength and lateral stability)
8)most 4 link setups are triangulated esp in a performance app anyway
9) the arms can move the wheel position fore or aft which can give clearance for larger tires near the front of the wheel opening (where it sometimes gets tight)
10)also lengthening or shortening the lca WILL change instant center so lift can be added or taken away from the front of the car
11) also pinion angle can be adjusted
12) I was concerned about the pinion offset on this rear before I installed it but found it to be identical with the 7.5 I removed
13) Brake lines actually bolted right up to stock t-block
14)parking brake took a bit of work
15) TRZ sells this kit and has done the R&D on it already in fact it has been used on many cars before mine You could visit their website trzmotorsports.com
they have a stock style suspension g-body (a pink bu I think) running 8.18 with a strangely similar setup (not sure what diff but arms are the same)
16) I just did my own R&D to make sure the vehicle will function properly
17) If your going to buy uppers and lowers anyway why not get ones that allow adjustability of the suspension rather than hoping the standard arms you get will achieve desired affects (unless possibly someone is intimidated by 4-link suspension tuning)
18) the wider rear also allows for more wheel options since a different bs will be used (a plus in my book)
I hope I answered all your questions. Believe me I did plenty of research before and during this swap and it is extremely well designed and laid out.
I realized I forgot to post a link to the other thread with all the info (including prices) so here it is
My G-Body 8.8 Rear End swap complete w/pics
The link I posted details the cost breakdown.
Basically I could have done it for about $800 (including the diff)and had a totally adjustable 4-link rear setup with disc brakes
For my application I chose to overbuild it a little and the price came out to about $1400 (I planon running nines with a turbo v-8 and a T-56)
gbodygmachine
Member
- Joined
- Nov 28, 2006
interesting
The Ford 8.8 has a smaller ring gear than the GM 12-bolt which is 8.875in. The GM 12-bolt has 30-spline axles while most mustangs have 28 splines, however some later (I can't remember when they changed but think its 05+) had 31 spline axles. The Ford 8.8 and GM 12-bolt share the same pinion bearing and both are C-clip axles. Unless you are running a 4 link with a Panhard or Watts Linkage it will be triangulated in what's called a Scatchel linkage after the GM engineer that came up with it, I can't comment on changing the angles effect on lateral control.
The 8.8 is just more prevelent, cheaper, and came with Disc brakes over its 8.5in 10-bolt production bretheran. When it comes to comparitive strength, the 28 spline 8.5in 10-bolt and the 28 spline 8.8in Ford are probably going to be roughly comparable. Upgrade them to the larger production axles (30spine GM and 31 spline Ford) and the Ford probably has the 8.5" beat but not by enough to consider it an upgrade one over the other. After all B-body Impala SS's get into the 11's on an Auburn or Eaton posied stock 8.5in 30 spline 10-bolt. Into the aftermarket you can get an aftermarket 12-bolt, 9in Ford, 8in Ford, and Dana 60, all will run you lots of money.
I don't like the split bolt pattern front to rear but overall this is a probably a cheaper swap than an 8.5 for those of us with 7.5in rears, even considering custom axles and a 30 spline posi.
The 8.8 is just more prevelent, cheaper, and came with Disc brakes over its 8.5in 10-bolt production bretheran. When it comes to comparitive strength, the 28 spline 8.5in 10-bolt and the 28 spline 8.8in Ford are probably going to be roughly comparable. Upgrade them to the larger production axles (30spine GM and 31 spline Ford) and the Ford probably has the 8.5" beat but not by enough to consider it an upgrade one over the other. After all B-body Impala SS's get into the 11's on an Auburn or Eaton posied stock 8.5in 30 spline 10-bolt. Into the aftermarket you can get an aftermarket 12-bolt, 9in Ford, 8in Ford, and Dana 60, all will run you lots of money.
I don't like the split bolt pattern front to rear but overall this is a probably a cheaper swap than an 8.5 for those of us with 7.5in rears, even considering custom axles and a 30 spline posi.
Hi CTX-SLPR
I noticed "USAF physicist" in your signature. My background is physics too. About 8.5" versus 8.8" versus 8.875", the differences in diameter are so small, that I wonder whether ancillary factors not explicitly related to ring gear diameter may be dominating the question of overall strength.
That's why I didn't presume that an 8.8" rear is stronger than an 8.5" rear, although in the absence of further information, the larger diameter should prevail. (To be more precise: it's not clear to me how strength goes with diameter, but it's not likely to vary by more than the cube in diameter, in which case an 8.8" rear should be not more than 10% stronger than an 8.5" rear. At that point, gear metallurgy and material properties differences could well overwhelm simple diametric considerations.)
Topher - thanks again for your answers. Do you have any data about weight?
Best,
MAP
I noticed "USAF physicist" in your signature. My background is physics too. About 8.5" versus 8.8" versus 8.875", the differences in diameter are so small, that I wonder whether ancillary factors not explicitly related to ring gear diameter may be dominating the question of overall strength.
That's why I didn't presume that an 8.8" rear is stronger than an 8.5" rear, although in the absence of further information, the larger diameter should prevail. (To be more precise: it's not clear to me how strength goes with diameter, but it's not likely to vary by more than the cube in diameter, in which case an 8.8" rear should be not more than 10% stronger than an 8.5" rear. At that point, gear metallurgy and material properties differences could well overwhelm simple diametric considerations.)
Topher - thanks again for your answers. Do you have any data about weight?
Best,
MAP
I didnt actually weigh either diff but I did end up having to lift them both by myself. If I had to guess a difference I would say 20-25 lb which I would imagine would be the same for 7.5 vs 8.5 I wouldn't consider this swap if I had an 8.5 either. Based on info I gathered on the swap I think there is a negligible difference in strength between the two axles. My reasons for the swap were the obvious 7.5 diff + desire for 4 wheel disc brakes + wanted to use 5.5 in bs wheels without cutting up my car + wanted a fully adjustable rear suspension + dont have alot of money = 8.8 for me. I hope this can be helpful for other financially challenged members as well since I searched for quite some time for an economical solution to my axles shortcomings.
Thanks so much for your feedback guys It is really appreciated.
MAP are you sure you dont make money on the side writing college exams and SAT tests (ancilliary metallurgy) :biggrin: Im not being a jerk, and yes I know what they mean, just giving you a hard time.
Thanks so much for your feedback guys It is really appreciated.
MAP are you sure you dont make money on the side writing college exams and SAT tests (ancilliary metallurgy) :biggrin: Im not being a jerk, and yes I know what they mean, just giving you a hard time.
Im just messing with you. There are alot of people on this site with very impressive credentials. That is why I like this site so much. people here tend to make me think outside the box which in turn, makes my project turn out much better. Thanks again guys! Chris
mousemobile
Member
- Joined
- Mar 13, 2003
Good idea for this. Using aftermarket control arms that are more flexible at the joints should eliminate any binding that MIGHT occur due to offset mounting points.
To use 31 spline axles in a SN95 you need aftermarket axle shafts. They are relatively cheap at about $220 / pair. Might as well spend a little more and get a dual bolt pattern. Dual pattern rotors available from the hot rod industry. They can also supply larger (Explorer) brakes (need modification to fit).
31 spline differentials can be found in trucks or high perf late model Mustangs. Late model axle shafts won't fit earlier housings. The Shelby uses carbon fiber discs. (Ford Motorsport) Or you can get an Eaton limited slip, Detroit locker, or Truetrac, etc.
I believe 35 spline axles can fitted to the 8.8 (drag race stuff).
The 2005 and newer Mustang 8.8s are wider, but all use vented disc brakes and 31 spline axles. If this fits, you need a wheel with a lot of backspace.
The gear metallurgy is good, since it is a high quality alloy steel. I think it is 9310, but I'm unsure.
As an aside, at Ford, the 8.8 with 28 splines is called the 8.5, the 31 spline version is called the 8.8.
Anyway, the strength is comparable (maybe excceding) to the 10 bolt or 12 bolt.
If you have questions about the 8.8, I can probably answer it. I was a Ford Engineer at the Sterling Plant, in-house manufacturing of all of Ford axles, gearsets, tubes, housing, etc.
my $.02 worth.
To use 31 spline axles in a SN95 you need aftermarket axle shafts. They are relatively cheap at about $220 / pair. Might as well spend a little more and get a dual bolt pattern. Dual pattern rotors available from the hot rod industry. They can also supply larger (Explorer) brakes (need modification to fit).
31 spline differentials can be found in trucks or high perf late model Mustangs. Late model axle shafts won't fit earlier housings. The Shelby uses carbon fiber discs. (Ford Motorsport) Or you can get an Eaton limited slip, Detroit locker, or Truetrac, etc.
I believe 35 spline axles can fitted to the 8.8 (drag race stuff).
The 2005 and newer Mustang 8.8s are wider, but all use vented disc brakes and 31 spline axles. If this fits, you need a wheel with a lot of backspace.
The gear metallurgy is good, since it is a high quality alloy steel. I think it is 9310, but I'm unsure.
As an aside, at Ford, the 8.8 with 28 splines is called the 8.5, the 31 spline version is called the 8.8.
Anyway, the strength is comparable (maybe excceding) to the 10 bolt or 12 bolt.
If you have questions about the 8.8, I can probably answer it. I was a Ford Engineer at the Sterling Plant, in-house manufacturing of all of Ford axles, gearsets, tubes, housing, etc.
my $.02 worth.
mousemobile
Member
- Joined
- Mar 13, 2003
Is the there any difference in control arm length? If so, would you provide dimensions?
Do you which year axle you're using? The 8.8 housing was the same width through 1998 (axle seal to axle seal). However, the shafts were lengthened to increase the track width from 1994 to 1998 (wheel mounting face). In 1995 through 2004, the housing and axles were both lengthened to make the axle wider.
Are you using the stock companion flange or did you convert to standard u-joint yoke?
In 2005, a complete redesign of mounting, brakes, bearings, companion flange, wider, bigger, etc.
I wish that I would of thought of this swap while I still worked at Ford.
EDIT:
Sorry, most of the the answers are at: http://www.theturboforums.com/smf/index.php?topic=104354.0
Do you which year axle you're using? The 8.8 housing was the same width through 1998 (axle seal to axle seal). However, the shafts were lengthened to increase the track width from 1994 to 1998 (wheel mounting face). In 1995 through 2004, the housing and axles were both lengthened to make the axle wider.
Are you using the stock companion flange or did you convert to standard u-joint yoke?
In 2005, a complete redesign of mounting, brakes, bearings, companion flange, wider, bigger, etc.
I wish that I would of thought of this swap while I still worked at Ford.
EDIT:
Sorry, most of the the answers are at: http://www.theturboforums.com/smf/index.php?topic=104354.0
Similar threads
