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TRip
Trip Anthony

(162 posts)

Registered:
08/18/2009 01:16AM

Main British Car:
1980 TR7 performance 4 cyl

Jag and some other IRS have off-center pinion - what's up with that?
Posted by: TRip
Date: August 28, 2009 04:42PM

Hello everyone,

I have decided on an IRS - a Jag or other IRS for my TR7 V8 project. I read the posts and comments here and I'm confused about what seems to be an off-centre diff. input pinion. I know that the engine, trans and shaft in my TR7 will be true down the centre. Logic tells me that the pinion needs to also be in line or simply won't work... I read comments about shifting the pinion to center and cutting the control arms and halfshafts. To me this then sets up handling issues and the same issue found in FWD cars ie: torque steer.

I know I want to avoid all of these issues and what looks like a huge amount of work.

Can another pumpkin be substituted. I've seen a Jag style unit with a Ford 9". Can the Jag be modified reasonably easily, or sholud I be looking at another unit entirely?

Can anyone clear this up for me or point me in another IRS direction?

Thanks,

Trip


danmas
Dan Masters
Alcoa, Tennessee
(578 posts)

Registered:
10/28/2007 12:11AM

Main British Car:
1974 MGBGT Ford 302

authors avatar
Re: Jag and some other IRS have off-center pinion - what's up with that?
Posted by: danmas
Date: August 28, 2009 09:40PM

Trip,

All differentials have an offset pinion. You can either center the pinion in the car and have different sized axles, or keep the axles the same and offset the pinion. If there is room for the driveshaft in the tunnel with an offset, I would prefer to keep the axles the same and put the pinion off center. As long as the centerline of the pinion is parallel to the centerline of the engine, it doesn't make any difference whether the pinion centerline is above, below, to the right, or to the left of the engine centerline.


TRip
Trip Anthony

(162 posts)

Registered:
08/18/2009 01:16AM

Main British Car:
1980 TR7 performance 4 cyl

Re: Jag and some other IRS have off-center pinion - what's up with that?
Posted by: TRip
Date: August 29, 2009 01:05AM

Interesting... After all this time, I always thought that it had to be aligned. What you say does makes sense. In a solid axle, there is always vertical movement and maybe some lateral too(?).

Even though this is the way it is, I just have to ask the question: Why then doesn't an off-center alignment setup cause A) torsion issues, B) huge amounts of premature wear, C) excessive strain on the bolts/mounts?

Do you know how many degrees in any direction is safe?

Thank you for the explanation, Dan.

Trip


74ls1tr6
Calvin Grannis
Elk Grove,CA
(1151 posts)

Registered:
11/10/2007 10:05AM

Main British Car:
74 TR6 / 71 MGB GT TR6/Ls1 71 MGB GT/Ls1

authors avatar
Re: Jag and some other IRS have off-center pinion - what's up with that?
Posted by: 74ls1tr6
Date: August 29, 2009 10:21AM

Here is some information on pinion angles!

driveshaftangles.jpg


TRip
Trip Anthony

(162 posts)

Registered:
08/18/2009 01:16AM

Main British Car:
1980 TR7 performance 4 cyl

Re: Jag and some other IRS have off-center pinion - what's up with that?
Posted by: TRip
Date: August 29, 2009 02:30PM

Calvin, thank you very much for the diagram...

I'm guessing that this also applies to a horizontal off-set. So a total of no more than 7 deg in any direction?

Do these angles also apply to coil and shock or coil-overs"?

Trip


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