Need info with a rear end swap from 88-98

[Sklptrljay]

This is regarding a 1971 C/10 coil spring truck.

I've been trying to find a 3.73 complete rear end for a while and without dropping some big $. I haven't found a direct replacement for a 71/72 5 lug coil spring. I'm avoiding 6 lug's, as purchasing the 5 lug axles will cost a good chunk and I don't want a narrower stance.

So...I found a 3.73 from a 88-98 for a decent price. I know I have to weld on saddles for the coil springs. I already have a super track bar.

Bottom line will this work or won't it.

[leftybass209]

A rear end is a rear end. If you are welding coil bosses on the axle and the track width is acceptable there's no reason just about any rear end wouldn't work.

[Sklptrljay]

So I did some research and it looks like it will work. I was hoping someone who has done this will chime in. I would feel better knowing I'm not going to run into any surprises. My concerns are, is the tube the same diameter, will the u joints be a direct fit to my driveshaft, and will the emergency brakes hookup give me any issues?

[airdale94]

Pretty sure that's the standard for rear end swaps. 88-98 5 lug. 3.42 for non overdrive and 3.73 for OD. TxFF was just talking about this the other day. Apparently 80% of them are 3.42 and the other 20% 3.73.

[GASoline71]

Just make sure it doesn't have the "gov-lock" posi-traction unit in it. Those are a greneade waiting to have the pin pulled.

Gary

[Sklptrljay]

Originally Posted by GASoline71

Just make sure it doesn't have the "gov-lock" posi-traction unit in it. Those are a greneade waiting to have the pin pulled.

Gary

Really. So avoid any posi of those years, or are there different types of posi for those?

[airdale94]

Originally Posted by Sklptrljay

Really. So avoid any posi of those years, or are there different types of posi for those?

Pretty sure they're all gov. lock. Maybe not the earlier ones. G80 is the code for locker. Posi or Ltd. slip has a different code. It should be easy to tell with the cover off, the posi will have clutch plates.

[68 TT]

Originally Posted by airdale94

Pretty sure that's the standard for rear end swaps. 88-98 5 lug. 3.42 for non overdrive and 3.73 for OD. TxFF was just talking about this the other day. Apparently 80% of them are 3.42 and the other 20% 3.73.

There are exceptions. My 89 C1500 came from the factory with no OD and 4.10 gears. On the SPID and still in the truck. My old 90 had 3.42's with OD.

The SPID label in the glove box is an easy way to see what was originally in the donor truck but is not always correct with what is actually in the vehicle. You still need to pull the cover to verify the actual gears in there.

There were also OEM clutch type posi carriers for the 30-spline 10-bolts but they are not very common and carry a high price tag used.

Not all G80 option codes were the ticking time bomb gov-loc. My 1990 Z71 came with the clutch type carrier in it.

If you can't find a stock one there are several aftermarket clutch type posi carriers out there in addition to the Detroit Truetrac as far better options to an open rear end or the gov-loc.

[57taskforce]

The gov loc isn't a ticking time bomb in the fact that if it fails it blows the rear end up. I've had two of them and when they fail they just act like a normal open diff. They have a fail safe built into them so they don't break the axles.

[snipescastle2]

yeah, you can buy the axle perches through Classic parts/LMC/Brother's etc... about $40.00 for both, you have to be pretty accurate with the pinion angle when you have them welded on the tubes of the new housing though.
HTH,
Ben

http://www.classicparts.com/1960-72-...ctinfo/93-319/

[Sklptrljay]

Thanks for all the replies. I have the rear end with the old brackets off, and I have the new saddles. Any advice on getting the pinion angle correct? My truck is lowered about 7 inches in the rear.

[EARNHARDT#3]

Originally Posted by Sklptrljay

Thanks for all the replies. I have the rear end with the old brackets off, and I have the new saddles. Any advice on getting the pinion angle correct? My truck is lowered about 7 inches in the rear.

Get one of these:
http://t.harborfreight.com/dial-gaug...der-34214.html

[57taskforce]

In my jeep days I used a magnetic angle finder on the bottom of the center section of the rear end. Best thing to do is have the pinion and drive shaft as close to a straight line as possible. Your gonna wanna set it at all ride height obviously.

[Boog]

I've not measured one but I believe the 88 up rear end is a bit wider than the older one. That's not going to mess you up with wheel/tire clearance is it?

[Sklptrljay]

Originally Posted by EARNHARDT#3

Get one of these:
http://t.harborfreight.com/dial-gaug...der-34214.html

Thanks, I have one already. I guess my question to be more specific is: How much should I adjust the pinion angle from stock on a truck lowered 7 inches.

[Sklptrljay]

Originally Posted by Boog

I've not measured one but I believe the 88 up rear end is a bit wider than the older one. That's not going to mess you up with wheel/tire clearance is it?

It is a little wider. I don't remember exactly how much, but I know it's going to put me right about where I want to be. It actually helps in my situation.

[Sklptrljay]

Originally Posted by 57taskforce

In my jeep days I used a magnetic angle finder on the bottom of the center section of the rear end. Best thing to do is have the pinion and drive shaft as close to a straight line as possible. Your gonna wanna set it at all ride height obviously.

I had a guy tell me that you want it slightly pointed down so when you get on the gas it will level out. I really don't want to get into advanced calculus to figure it all out, but that said I do want to get it right the first time.

[57taskforce]

Originally Posted by Sklptrljay

I had a guy tell me that you want it slightly pointed down so when you get on the gas it will level out. I really don't want to get into advanced calculus to figure it all out, but that said I do want to get it right the first time.

In all honesty I did a cut and re weld on the knuckle "c"s on my dana 30 to correct castor and driveline vibes so that's how I set it up. I didn't have to mess with the rear so in hindsight my original comment may have been misleading. My apologies but I can see having it pointed a little low to allow it to rotate it probably wouldn't take much however.

[SCOTI]

This was asked earlier but I never noticed an answer.... The 88-98 rear housings are about 1.5" wider (total) than the 71-87 5-lug housings.

[hugger6933]

I think about 2 degrees negative is where the pinion angle is happiest. but that is old info from hotrod racecar days long gone by but I think it is still in the range of acceptability. [2 to 4 n] I think is the spec. Some one else will correct me if I'm wrong. Jim

[lowbucktrucks]

make a frame of 2x4's and bolt your old axle to it and measure the angle. bolt the new axle brackets to same hole, center the rearend and set to same angle. weld

[lowbucktrucks]

search for "another 65 c20 14 bolt conversion" at this site for pictures of this

[Sklptrljay]

Originally Posted by lowbucktrucks

make a frame of 2x4's and bolt your old axle to it and measure the angle. bolt the new axle brackets to same hole, center the rearend and set to same angle. weld

Thanks, keep it simple right? That is a great idea. This site is an invaluable resource. Do you agree with what was said about a 2-4 degree negative angle?

[67 chevelle]

Originally Posted by lowbucktrucks

make a frame of 2x4's and bolt your old axle to it and measure the angle. bolt the new axle brackets to same hole, center the rearend and set to same angle. weld

Great advise ,,,would make it easy ,,,through the holes in the pinion and bracketed to the holes in the trailing arm brackets ,,, and coil spring buckets

[lowbucktrucks]

copy angle from original setup to keep angle equal to trans search for "another 65 c20 14 bolt conversion" at this site for pictures of this