Eaton LSD

XR4Ti / Sierra / Sierra Cosworth Discussions - Questions, problem resolution, general talk, technical tips and modifications.
lucassXR
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Post by lucassXR » Thu May 24, 2007 6:24 pm

also what make year did you get this diff out of? and did you have to do anything else with the axels/drivshaft or grinding on the case? I was seriously thinking about getting rid of the merk until I read this.

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Grayson
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Post by Grayson » Thu May 24, 2007 6:39 pm

You were going to get rid of your Merkur because there previously wasn't a way to use a GM differential in the stock housing without grinding?

Ben has some information on which differential to purchase. There are usually two styles of GM diffs - one is for gears that are numerically 3.27:1 and below, and one is for gears that are numerically over 3.27:1. I think based on a conversation I had with Ben a few weeks ago we are to use the numerically 3.27:1 and lower version, but hopefully he'll chime in with the confirmation.

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Post by lucassXR » Thu May 24, 2007 7:00 pm

Well to be honest I have had the worst of luck with this car. I have owned it for a month and have not been able to drive it for more than 4-5 days with out something new going wrong. It is old but most of it is just crap that the guy I bought it from didnt tell me about. I dont want to spend a crap load on an lsd. I am drifting this car this year and this is the biggest mod for me to do. everything else will be easier. Pretty much I am just a little fed up with the car...but this brings some light. It is way more powerfull than my 240sx that I sold. I am running 20psi right now. I just need to know what year and what kind of mods other than the shimming.

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Post by lucassXR » Thu May 24, 2007 7:01 pm

thanks for the info thus far :wink:

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Post by DSPXR4ti » Thu May 24, 2007 7:07 pm

Ok, just to inform you guys about what I did, You have to use the 3:27:1 and up, it's the one that work the best and then work off the rest of the info I posted, the springs I used were the one that the Eaton comes with 200lbs 400lbs 600lbs I'm not sure what the Eaton guy said but they have yellow paint on the springs, so go with those, make sure you do the break in your you will jack up the clutch's.

Ben DSP XR4ti

lucassXR
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Post by lucassXR » Thu May 24, 2007 7:14 pm

Ok i think I am confused. Eaton, is this the name of the unit that GM uses? Also what year and vehicle is this off of? Maybe I am misunderstanding.
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Post by DSPXR4ti » Thu May 24, 2007 8:10 pm

It the Vega 7.5 with the 3:27:1 and up GM Diff, with an Eaton LSD, please read all the posts.

Ben DSP XR4ti

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Post by Grayson » Fri May 25, 2007 11:28 am

I believe that this is the Eaton clutch-style unit:
http://store.summitracing.com/partdetai ... toview=sku

Here is the Eaton Detroit TrueTrac Torsen-style unit:
http://store.summitracing.com/partdetai ... toview=sku

Here is a Strange "standard" unit:
http://store.summitracing.com/partdetai ... toview=sku

Another Strange "pro" unit:
http://store.summitracing.com/partdetai ... toview=sku

Auburn standard unit:
http://www.jegs.com/webapp/wcs/stores/s ... 2_15046_-1

Auburn pro unit:
http://www.jegs.com/webapp/wcs/stores/s ... 2_14422_-1

Ben - do you have the exact Eaton part number that you purchased? That would eliminate all confusion.

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Post by DPDISXR4Ti » Fri May 25, 2007 12:28 pm

A minor data point, but the cross-over ratio where GM changes things is 3.23. 3.27 is a typical Ford ratio.

Lots of GM's use the 7.5 26-spline rear - technically, I think it's 7.625" - which is part of the reasoning for why the modifications are required to fit it into the Euro Ford 7.5 case that our cars have.

As I understand it, Eaton was the primary supplier of differentials to GM, but as Grayson points out above, after-market options exist. They *probably* all fit, but I'm only aware of the Auburn and Eaton having been fitted.
Brad

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Post by DSPXR4ti » Fri May 25, 2007 12:57 pm

Hello All,

Here is the web page that I got my Eaton from www.reiderracing.com and the part number is gm7/p426 the cost for my Eaton was 325.00, so I'm not sure what summit is doing, except for one good profit margin, call them and ask them for more info on the Eaton and others you may have a better Ideal but the Eaton is what I know that fits.

Ben DSP XR4ti

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Post by whitelx » Fri May 25, 2007 5:28 pm

I'm going to have to do some JY searching. I'd like to experiment first with a JY part then order up the Detroit Tru-Trac sometime later (after I figure out trans and rear gear ratios).
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Post by DPDISXR4Ti » Fri May 25, 2007 5:46 pm

whitelx wrote:I'm going to have to do some JY searching. I'd like to experiment first with a JY part then order up the Detroit Tru-Trac sometime later (after I figure out trans and rear gear ratios).
I seem to recall that there's a way to decipher the ratio and LSD or not via the VIN sticker or maybe some sort of ID badge in the glove-box? Maybe search around the 'net and you'll find the info. S10's and Blazers were the most likely candidates. A lot of RWD car GM products had ratios in the 2.7x neighborhood, and those won't be right (see comment above re: 3.23 or higher).

Pretty sure you'd be blazing new ground with trying to fit a GM 7.5 Tru-Trac. I know that generally speaking, Tru-Tracs are physically bigger, so you may have an issue with needing to grind too much of the case to be able to get it in there.
Brad

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Post by lucassXR » Fri May 25, 2007 7:06 pm

In another post...http://www.turboford.net/ubb/ultimatebb ... 000014;p=1
aplications fo rthe GM 7.5 are
82-90 s10, and f body
85-89 astro and safari vans

From what I can tell you can use the stock unit and should only have to elongate the holes for th pinion gear? The only reason you would have to grind anything would be from using the aftermarket replacement diff this was what the guys typed "stock units 112mm diamiter
the auburn is 115mm... just enought to get in the way on my dif
"
It is a bit difficult to sort through alot of the old posts with pictures as they are from like '03 '04 and the pics are gone.
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Post by flylear45 » Fri May 25, 2007 10:01 pm

If I recall, Harry King was once experimenting with a True-trac in a Merkur diff. He got busy with babies and such, so I doubt if he has any new info, but may be worth dropping an e-mail to him. He is a TurboFord member, and may even be registered here.
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Post by DPDISXR4Ti » Sat May 26, 2007 9:40 am

flylear45 wrote:If I recall, Harry King was once experimenting with a True-trac in a Merkur diff. He got busy with babies and such, so I doubt if he has any new info, but may be worth dropping an e-mail to him. He is a TurboFord member, and may even be registered here.
Yep, I recall Harry was looking into that several years back, but I don't think he ever got as far as even a test fit. And really, the only thing that would prevent anyone from using this diff is if it doesn't physically fit into the case without excessive clearance grinding. I am pretty certain it will require SOME grinding.
Brad

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