Converting 8 3/4 open rear end to Sure-Grip

[oldchevelle541]

In the future I may want to convert my open rear end with 3:23 to a sure-grip unit. What all has to be done and how do you know a used sure-grip unit is in good shape before you buy one. This is for a 1969 GTX with automatic.

 

[493 Mike]

Just purchase a new unit?
Mike

 

[4mulas]

You need a sure grip carrier to replace the open carrier and then install the gears etc…. Setting up used gears in a new carrier/suregrip set can be difficult. Maybe look for an all new unti if you’re going as far as a new carrier anyway. You’ll want all new bearing etc too

People often sell good used ones ready to roll as well

 

[wish4hemi]

All right here:

Gallery: Installing Eaton’s Truetrac in a Chrysler 8.75” Rear; Comparing Cast Cases - Mopar Connection Magazine | A comprehensive daily resource for Mopar enthusiast news, features and the latest Mopar tech

 

[toolmanmike]

Contact Dr Diff for Sure Grip units. You will need to know which housing you have.

 

[ckessel]

I'm going to replace the a/m power lock unit in my wagon to the sure-trac2 unit sometime in the future. The PL unit has had a popping/chatter issue since I've owned the car. The PO put in 2 bottles of modifier, but it still complained. After I switched the cross shaft, am running tapered axle bearings now, it has gotten worse.

 

[oldchevelle541]

Contact Dr Diff for Sure Grip units. You will need to know which housing you have.

I heard of him......thankyou.

 

[Rebelrouser]

In the future I may want to convert my open rear end with 3:23 to a sure-grip unit. What all has to be done and how do you know a used sure-grip unit is in good shape before you buy one. This is for a 1969 GTX with automatic.

Buy the suregrip differential, and before you take the old ring and pinion apart measure the backlash, since the pinion does not need to be removed the pinion depth will not change. Install the ring gear on the new suregrip and set back lash where it was before, making sure the side bearing peload is correct.

 

[Cranky]

In the future I may want to convert my open rear end with 3:23 to a sure-grip unit. What all has to be done and how do you know a used sure-grip unit is in good shape before you buy one. This is for a 1969 GTX with automatic.

The new SG's are usually coming from China (at least the last SG I got from Dr. Diff was) but it's still possible to find originals in good condition. DO NOT remove the pinion gear. If you have a dial indicator, check the backlash on the gears with the open with the open unit before pulling it out. This check is easy to do. If no dial indicator is available, just do it by feel with a feeler gauge.

This way you can set the 'new' carrier to the same specs or at least be within a couple of .001's. Both the cone type and the clutch plate type come apart. The ring gear bolts are left handed but the carrier half bolts are not. I've done this many many times and never had an issue with gear noise. If you do this, just take your time. My first time in the 80's went slowly but wasn't hard to do.

Also I have a couple of cut off axles that I welded a T bar to them as test tools and also use one as an assembly tool. Too bad you are so far away because I would just give them to you as I don't do rear end work anymore. My back won't let me pick up an 80 lbs 3rd member anymore.

 

[PurpleBeeper]

In the future I may want to convert my open rear end with 3:23 to a sure-grip unit. What all has to be done and how do you know a used sure-grip unit is in good shape before you buy one. This is for a 1969 GTX with automatic.

Basically, you pull out the “open” center section and install the “sure grip” center section using sure grip rear end lube and you’re done. Any of the 3 types of center sections will work. I’ve had very good luck just installing used sure grip center sections

 

[oldchevelle541]

Thanks, will look for a good used OEM unit that was used lightly. I just dont want anything on my GTX from China.

 

[Cranky]

Thanks, will look for a good used OEM unit that was used lightly. I just dont want anything on my GTX from China.

Keep in mind that this stuff is getting old but there probably are some of the bigger cars that have a 'lightly' used SG in them. I found a couple years ago (80's) in C body cars and they were like new while stuff in high performance cars were pretty used up.

 

[71RRHI]

They come up for sale all the time this one just posted recently.

R

SOLD Thread '8 3/4 Sure Grip 3.55 489 Case'

Friday at 8:46 AM

8 3/4 Sure Grip 3.55 489 Case. Great Shape.

$850 obo

• ROB SHARON
• Replies: 7
• Forum: Mechanical Parts For Sale

 

[oldchevelle541]

Keep in mind that this stuff is getting old but there probably are some of the bigger cars that have a 'lightly' used SG in them. I found a couple years ago (80's) in C body cars and they were like new while stuff in high performance cars were pretty used up.

thats my concern, find a used one that is worn out or go buy new and made in China.

 

[4mulas]

I just dont want anything on my GTX from China.

Good luck with this.

 

[oldchevelle541]

I will educate myself first then make the decision. It's winter here so no rush but thankyou.

 

[Lefty71]

I will educate myself first then make the decision. It's winter here so no rush but thankyou

For what its worth....some of us have bought the unit that Dr Diff sells....fits in the open carrier, works awesome and no clutches or cones to wear.

 

[1KoolBee]

Find a “Clutch Style” sure-grip unit from a pre ‘69. It can be from a 741 or 742 case, they are same and will fit a 489 case as well. The 2 halves of the posi bolt together and it’s easy to disassemble. Once inside, inspect the clutch plates. If they are chewed up, galled or heavily worn, replace them with new plates. You’ll have to stick your axles into the posi to make sure the clutch plates stay aligned while you tighten the case halves. Inspect the carrier bearings, they can be used again if they are clean and in good shape ( no pitting, galling, heat damage) . On mine, I take the SG unit to a machinist and have him check the runout of the ring gear mounting face on a lathe. I’ve had him cut up to .005 off the face to true it up. Makes getting consistent backlash adjustment way easier. Once everything checks out, install your ring gear , install carrier , install bearing cups, caps and carrier adjusters. Only moderately tighten upper carrier cap bolts, install lower bolts hand tight. Adjust left carrier adjuster until you have about .001-.002 backlash. Then tighten right adjuster until you have .005-.007 backlash. Check backlash in 4 places. Should be consistent . Torque carrier caps to spec, and install in car.