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8.25 swap process question


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Hi all,

I have read several threads on the 8.25 swap but have a few clarifying questions on the overall process. I plan to install an 8.25, staying SUA, with a 1" lift shackle with the idea of going to a GS MT spring pack later on. rear brakes will stay the stock drums.

 

--Brake lines: am I good on existing brake lines from the comanche? They will screw into whatever is attached to the drums on the 8.25? 

 

---Emergency brake: will I need any adapters or plates to fit the cable from the MJ? 

---Driveshaft length: with a 1" lift shackle on semi-tired springs, do you reckon the yoke will bang on the back of TC? If yes, how much lift do I need to use to my existing DS? 

 

---Pinion alignment/rear axle install: Can I install the axle by:

1. loosely attaching new perch brackets and u-bolts to properly align the pinion

2. tighten down u-bolts

3. Drive somewhere that can weld the perches to the axle as it sits

Or do I need to:

1. Loosely install perches

2. Mark axle for places to weld perches

3. uninstall everything and weld perches

 

Ideally, I'd like to drive it under the support of u-bolts only, but fully installed, to guy who can weld it all in place. That may be wishful thinking. 

 

Thank you all for the great advice. 

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Hi all,

I have read several threads on the 8.25 swap but have a few clarifying questions on the overall process. I plan to install an 8.25, staying SUA, with a 1" lift shackle with the idea of going to a GS MT spring pack later on. rear brakes will stay the stock drums.

 

--Brake lines: am I good on existing brake lines from the comanche? They will screw into whatever is attached to the drums on the 8.25?

 

I used a stock type extended hose from the body to the axle using the originally application as a base

 

---Emergency brake: will I need any adapters or plates to fit the cable from the MJ?

 

Don't know. My stockers were too short after SOA

 

---Driveshaft length: with a 1" lift shackle on semi-tired springs, do you reckon the yoke will bang on the back of TC? If yes, how much lift do I need to use to my existing DS?

 

There is a list of driveshaft lengths on here. The stock length for my combo works with my SOA so about 5.5" f lift is needed to make up tha 1". I would be concerned about your stock drive shaft as it should be an inch too long for an 8.25 at less loft. I have read that you can use a chop saw to shorten the yoke into the trans by up to an inch

 

---Pinion alignment/rear axle install: Can I install the axle by:

1. loosely attaching new perch brackets and u-bolts to properly align the pinion

2. tighten down u-bolts

3. Drive somewhere that can weld the perches to the axle as it sits

Or do I need to:

1. Loosely install perches

2. Mark axle for places to weld perches

3. uninstall everything and weld perches

 

Step 2. Tightening the bolts will probably not be enough when you apply the torque to move the truck

 

Ideally, I'd like to drive it under the support of u-bolts only, but fully installed, to guy who can weld it all in place. That may be wishful thinking.

 

Thank you all for the great advice.

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So here is another question: Do you think I can accurately measure the angle of the pinion relative to the perches as they are sit on my D35 and weld the perches onto the axle prior to installation? I would worry that the extra thickness of the 8.25 might effect that angle. If I can't bolt up the rear and drive it to a welder or weld using measurements, it sounds like I will need to find a welder who makes house calls.  

 

Regarding the DS, it looks like a comanche with an AW4/231/D35 has a 1" shorter shaft. 

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