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#984308 - 09/28/13 04:02 AM Moser Differential  
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Cos86SS Offline
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Westfield, MA
Brought my SS to the transmission shop to find out what is causing my vibration at 65mph. You could feel the vibration through the floor board. They found that when you spin the yoke (part that connects to the drive shaft) you can feel some tension while your spinning it. So I need to rebuild the differential. It looks like I will have spend around $1300 when all done. The owner of the transmission shop asked me if I want to consider going with a Moser 8.5 inch (I believe this is also called a 12 bolt). He believes it will be around $2000 but he is going to check prices on Monday. Anyone using the Moser differential 12 bolt? I have read on this forum that the shocks won't line up. Is this a major project to correct and will it drive the cost up? Is it a worthwhile upgrade? Motor isn't making huge HP now but you never know what the future holds.


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#984314 - 09/28/13 11:45 AM Re: Moser Differential [Re: Cos86SS]  
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GuysMonteSS Offline
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If more HP is in your future,a stronger rearend would be a required upgrade,IMO.If its only $ 700.00 more for a complete rear over a rebuild,I would go for a new one.
You may want to make sure that you are getting a complete ready to run package for that price.Brakes may be extra,or possibly the old ones could be re-used.
Guy


GuysMonteSS '86 SS,513 BBC,AFR Heads,UDHarold/Bullet Custom Solid Roller Cam,706 lift,255/263 @ .050,Jesel Shaft Rockers,Balanced & Blueprinted,Doug Nash 4+1 5 Speed,Hurst In-Line Shifter,Ford 9 Inch Rear,SC&C Street Comp Stage 2+ Front End Kit...
#984316 - 09/28/13 12:03 PM Re: Moser Differential [Re: Cos86SS]  
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Joe87monteSS Offline
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A few things. A 12 bolt is NOT an 8.5 rear. Those are two different things. A 12 bolt has an 8.875 inch ring gear vs. the 8.5 10 bolt. If it is an aftermarket unit, it will be specific for the G body.


Joey
Engine/head builder/machinist
1987 Monte Carlo SS 383/4 Speed
2004 Silverado
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#984322 - 09/28/13 03:25 PM Re: Moser Differential [Re: Joe87monteSS]  
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1 Slow SS Offline
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I have one and the shocks line up perfect. Just incert a tappered shim inbetween the shock and mounting plate.

The 12 bolt rear is an upgrade. But for 2K it won't be nothing that good. What do you have under the hood?


Enjoy life, family first!
#984354 - 09/29/13 02:01 AM Re: Moser Differential [Re: 1 Slow SS]  
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Cos86SS Offline
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Westfield, MA
Originally Posted By: GuysMonteSS
If more HP is in your future,a stronger rearend would be a required upgrade,IMO.If its only $ 700.00 more for a complete rear over a rebuild,I would go for a new one.
You may want to make sure that you are getting a complete ready to run package for that price.Brakes may be extra,or possibly the old ones could be re-used.
Guy


I'll make sure I know what I am getting for the price he quotes me. If it's well above 2K I will most likely pass.

Originally Posted By: Joe87monteSS
A few things. A 12 bolt is NOT an 8.5 rear. Those are two different things. A 12 bolt has an 8.875 inch ring gear vs. the 8.5 10 bolt. If it is an aftermarket unit, it will be specific for the G body.


That would explain why I could not find a 8.5" on their website. If I go for the new differential I'll make sure that no other modifications will be required or else the price will go up.

Originally Posted By: 1 Slow SS
I have one and the shocks line up perfect. Just incert a tappered shim inbetween the shock and mounting plate.

The 12 bolt rear is an upgrade. But for 2K it won't be nothing that good. What do you have under the hood?


I am running a SBC 355 with double hump heads (1.94" valves, 63cc) and a Comp Cam Roller Cam (XR276HR-10). I am under 300HP but if something ever breaks, first thing I would do is upgrade the heads for more power. I am not looking for anything that can handle huge HP but just a better unit than the 7.5" if the price is right. It's good to know that it should fit if I decide to go for it.

I'll know more on Monday and will let everyone know what I decided on. Thanks for everyone's input.


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#984412 - 09/30/13 12:51 AM Re: Moser Differential [Re: Cos86SS]  
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mikester Offline
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Im one of the people that had a problem with a Moser 12 bolt. Theres also a guy on turbo buick that's going through almost the same thing right now. My rear was close to $3K. The spring perches were welded in the wrong place. My springs wouldn't fit right. Moser sent me a new rear but it was only after I argued with the production manager. The new rear came with the spring perches in the crate so they could be welded on during the install. As far as the shocks, no they don't line up right and they have to be played with. Not what I expected for a direct replacement rear. From what Ive read it doesn't matter what brand rear you buy, its all the same way.

Last edited by mikester; 09/30/13 12:53 AM.
#984430 - 09/30/13 03:47 AM Re: Moser Differential [Re: Cos86SS]  
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Cos86SS Offline
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For $3K one would expect a direct fit. Since I'll be having mine installed by the Transmission shop i would expect them to make sure it is a direct fit without any mods. I wonder if the 8.5" is a direct fit. It's what the transmission shop recommended. Besides I do not want to spend more than $2K.


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#984563 - 10/02/13 12:21 AM Re: Moser Differential [Re: Cos86SS]  
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NYmonteSS Offline
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You can get a 8.5 out of an Olds 442, Buick GN. Stock these will handle what you have with no problems at all and a lot more.
Its a direct swap in, you can get them for $1000 and under sometimes.

This would be the cheapest and good upgrade from the 7.5.

so figure $ wise
$ 1000 for the rear, complete, drum to drum
$ ? shop install labor price
$25 fluid & gasket & RTV

You could be in a area of $1400 $1500 by the time your done!


Pres: www.NYMonteCarloClub.com

Its quick!!!


#984571 - 10/02/13 01:28 AM Re: Moser Differential [Re: NYmonteSS]  
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Cos86SS Offline
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Westfield, MA
Originally Posted By: NYmonteSS
You can get a 8.5 out of an Olds 442, Buick GN. Stock these will handle what you have with no problems at all and a lot more.
Its a direct swap in, you can get them for $1000 and under sometimes.

This would be the cheapest and good upgrade from the 7.5.

so figure $ wise
$ 1000 for the rear, complete, drum to drum
$ ? shop install labor price
$25 fluid & gasket & RTV

You could be in a area of $1400 $1500 by the time your done!


I am already at$1300 if I need new Pinion and gears for the 7.5. I haven't heard from the transmission shop yet but I am calling them tomorrow to find out what is going on.

Thanks for the info.


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#985326 - 10/11/13 01:24 AM Re: Moser Differential [Re: Cos86SS]  
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Cos86SS Offline
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I called the transmission shop today and the plan is to rebuild my stock 7.5". Turns out that they could not find an 8.5" in my price range. I was told that an 8.5" would cost $3K and it's not even a direct fit. The tranny guy told me that all the places he had contacted told him that he would have to make major modifications to make it fit including welding. $3K is more than I am willing to spend. Now I just hope that the rebuilt diff. will take care of my vibration issues. Should know tomorrow if it helped. Thanks everyone for your help.


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#985510 - 10/13/13 07:30 PM Re: Moser Differential [Re: Cos86SS]  
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Frederick, MD
sounds like they were talking about using a leaf spring 8.5 out of a truck and welding brackets to it and cutting the tubes to make it fit for the 3K price. If they rebuild the factory unit get a good ring and pinion, not just a cheap stock replacement. Also now is the time to upgrade to a taller gear if you were planning it. Also possibly upgrading the axles to something to help hold some additional power.

#985537 - 10/14/13 03:29 AM Re: Moser Differential [Re: Cos86SS]  
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Cos86SS Offline
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No Cheap stuff. I made that clear when I dropped the car off and the guy agreed with me. I am sticking with the 3.73 ratio. I sometimes go on the highway and the 3.73s are just right. Should be picking up the car tomorrow. wasn't ready on Friday. GM send him the wrong Yoke.


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#985586 - 10/15/13 01:04 AM Re: Moser Differential [Re: Cos86SS]  
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Cos86SS Offline
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Picked up the car today. vibration at 65mph and above is gone. I still have a vibration through the steering wheel which was there before. It seems to vibrate from low speeds upto 85mph (Had to bring it up to 85mph to make sure the differential problem was fixed). I had the steering wheel vibration before I lowered the car 2 years ago but the vibration from the differential was much worse. Now that that's taken care of where should I look for the steering wheels vibration? How can I rule out the motor? Thanks,


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#985599 - 10/15/13 11:27 AM Re: Moser Differential [Re: Cos86SS]  
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MikesMontes Offline
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steering wheel vibration should in wheels and tires ---have you had them balanced lately


www.mikesmontes.com
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We have all your 4th Gen Monte Carlo needs
#985634 - 10/15/13 11:52 PM Re: Moser Differential [Re: Cos86SS]  
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Cos86SS Offline
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Westfield, MA
Hi Mike,
Yes, I had them balanced 2 years ago when I first noticed the vibration through the steering wheel. The balancing did nothing. I have had this problem prior to lowering the car 2 years and it's one of the main reasons I redid the suspension (New shocks and springs) but that also did not help with the vibration. I know I have a lot of play in my steering wheel due to wear and tear (steering box), could this be the cause assuming my tires are ok?


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#985637 - 10/16/13 12:15 AM Re: Moser Differential [Re: Cos86SS]  
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MikesMontes Offline
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rotate fronts to back ---still should be wheels or tires


www.mikesmontes.com
1-800-811-5851
We have all your 4th Gen Monte Carlo needs
#985642 - 10/16/13 01:18 AM Re: Moser Differential [Re: Cos86SS]  
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AkronAero Offline
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Need and alignment?
On rare ocassion you can have a bad tire (say, belt separation) which won't give constant balance... are you confident of the tires? Wear uneven?

#985646 - 10/16/13 01:52 AM Re: Moser Differential [Re: Cos86SS]  
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Cos86SS Offline
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There is no uneven wear. The tires are 3-4 years old and they look new. I could most certainly have a belt problem. Perhaps rotating the fronts to back as Mike suggested would be the easiest thing to try. The rears are 245s vs. 235s in the front but hopefully they wont rub on the inner fenders.


86 Monte Carlo SS W/T-Tops 'Original Owner'
355 CI, Hooker Super Comp Headers, True Dual Exhaust, Comp Cam Roller Cam (XR276HR-10), Q-Jet Carb 795CFM. 200-4R Transmission. 2" Lowered Suspension.
#985660 - 10/16/13 01:13 PM Re: Moser Differential [Re: Cos86SS]  
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even for a trial run of a few hundred miles, just to check the balance.

#985663 - 10/16/13 01:56 PM Re: Moser Differential [Re: Cos86SS]  
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245's will fit up front with out any trouble


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