8 3/4 Axle Question

[Tirekickertoo]

Hi Everyone,
I'm having a problem trying to install/bench fit the left side (drivers side) 8 3/4 axle into a 742 center section. It's a project I'm finally getting to this summer after a number of years sitting in dry storage. Here's the story... A few years ago I purchased a used complete 8 3/4 rear end out of a 1973 Dodge Challenger. It was a complete 8 3/4 original axle assemble that had an open 489 case. I then found and purchased a used 742 center section with a clutch type Sure Grip with 3:23 gears. I removed the 489 center section and installed the 742 Sure Grip center section into the 8 3/4 axle housing. I'm now trying to install/bench fit the original axles into the 742 center section but have run into problems. The drivers side axle does not want to fully seat into the 742 center section. It sounds like the axle is bottoming out inside the 742 center section. The passengers side axle fits fine, no issues. Just for kicks, I purposely swapped axle shafts. The problem remains on the drivers side only. I inspected the 742 Sure Grip before installing into the 8 3/4 axle housing. The thrust button is there and I don't recall seeing any spline damage. I'm sure I'm missing something. There's a ton of information on these 8 3/4 axles but I don't recall seeing this problem. I think I read somewhere that possibly the axle has to be twisted/torqued to install fully seat into a clutch type Sure Grip? I don't know if there is any truth to that statement. Attached are a few pictures of what I'm dealing with.

Thanks in advance for your help,

Tirekickertoo

 

[Chryco Psycho]

AS long as the button is still in place that is good as it is a pain to drop the center section to get it back in .
so the next issue is are all the splines lined up ? you can get through the side /axle gear but then you have to go through the plates between the clutches , you may have to twist the axle with a long pry bar & work your way through the plates one by one , this will not be easy as the sure grip will do its job locking the plates between the clutches

 

[704406]

I think Chryco Psycho is right about the splines being the problem. The clutch pack splines may not have been lined up exactly on the left side when the two halves of the sure grip were bolted together.
I always installed both axle's in the sure grip unit to make sure the splines were lined up and bottomed on the centre button, prior to tightening up the two halves of the sure grip assembly. Try the pry bar method, but you may find that you have to disassemble the unit to get the clutches to line up properly.
check the centre button's as well to make sure they go back and forth in the centre block, as that could also keep the axle from going all the way in

 

[AUSTA]

Also back the axle freeplay adjusting nut on the passenger side it may be turned right in causing the axle to hit the button to early.

 

[DetMatt1]

Great advice! This is yet another example of why forums like this one are a tool for the top drawer of your toolboxes.

 

[Tirekickertoo]

Thank you everyone for your knowledge and advice. Since the problem is only on the left side, I want to try and align the splines using the pry bar method. It will be a bit of a struggle since the rear end is on the bench. Using the pry bay method, is the clutch pack spring loaded? Meaning will I have push back on the pry bar? Or, will it will be a tight move since I will be trying to move only one axle only against spring downward pressure on a clutch pack. I'm a little green on this that's why I'm on this fourm. Thanks AUSTA on the advice about the axle freeplay adjusting nut possibly being turned in too far. Unfortunately this is not the issue. The problem still exists with the passengers side axle removed. I'm not really sure how the left side splines became misaligned? Is this a common problem or a wear problem? I bought Sure Grip/center section used but in nice shape. I had the center section shipped on the back of a UPS truck for about 400 miles. Would shipping cause this issue?

Thank you,

Tirekickertoo

 

[Steve340]

Are both axles you have the same length?
One should be around 3/4 to 1 inch shorter than the other.

 

[704406]

Shipping would not cause this issue. The clutch and friction disc's are cupped, so as the two halves of the differential are pulled together by the case retaining bolts the disc's "straighten out" putting clamping force against each other.
Trying to move the clutches while the axle is on the bench is probably going to be difficult. You'd have to hold the yoke and the opposite axle from turning.
If the clutches are causing the problem it's likely an issue that was caused when the unit was assembled, it doesn't take much to cause a problem.
I learned this the hard way, I tried to align the clutch splines by eye, needless to say thats where I learned to use the two axles to align things while tightening the case retaining bolts, and soaking the clutches and the disc's in rear axle lube and additive to eliminate chatter on corners right from the start

 

[Tirekickertoo]

Steve340,
I'm not sure of a difference in axle lengths? I'll have to measure and reply with my findings. I've haven't heard of different axel lengths before now. What I can tell is that the axle shafts are original to the rear end. The only thing different is the 742 Sure Grip center section. Yesterday I temporally swapped the drivers and passengers side axle shafts. The problem (gap) is always on the left side/drivers side of the center section.

Thank you,

Tirekickertoo

 

[Steve340]

Hi it may not be your problem but in hypoid type live rear axle one shaft is always shorter due to the offset of the crown wheel gear in relation to the pinion gear.

 

[704406]

The right side axle has the bearing end play adjuster.
You always put the drivers side axle in first and tighten the 5 retaining bolts. Then the passenger side axle so that the adjuster can then set the axle bearing end play off the centre button in the differential
The parts book lists both axles as being the same length part # 2800182 27 and 11/16"
The axles fit Cuda and Challenger 70-71 all with 8 3/4 rear axle

 

[Tirekickertoo]

Thanks everyone for sharing your experience. Today I borrowed a fiber optic camera from a friend to get a close up view of the drivers side splines. The camera is a cool tool that sells at Harbor Freight and costs under $100.00. With the camera I was able to confirm that the splines are not aligned. With some help I will attempt the pry bar method to try and align. If unsuccessful I’ll have to pull the center section. I’ll post my results soon. Awesome responses, thanks for the help. Tirekickertoo

 

[Tirekickertoo]

Hey everyone,
I wanted to give an update on the Sure Grip center section and the misaligned axle splines. With some help I attempted to align the splines using the pry bar method mentioned earlier in the post. Due to the rear end being on a bench, it was impossible to make this method work. This morning I pulled out the center section and am now attempting the loosen the Sure Grip differential case bolts to reduce clutch pressure to align the axle clutches/splines. Looking at the shop manual, (pg. 3-42, 3-53 or pg.100, 111 pdf file computer shop manual download) I'm reading that the torque spec. on these eight bolts should 45 foot pounds. I'm having a difficult time trying to loosen these eight bolts. I know there is pressure from the clutch plates, so I'm trying to loosen the bolts a little at a time. I'm a newbie in this area so I'm asking if what I'm describing is normal? I'm using a 1/2" drive socket with a 2" breaker bar and these bolts tight. Below are pictures of the misaligned axle splines etc.

Thank you,

Tirekickertoo

 

[Tirekickertoo]

Hi everyone,
I mentioned above that I'm having issues removing the eight differential case bolts. I stopped what I was doing and asked the question on this fourm. I just watched a youtube video on rebuilding a Sure Grip center section and was told that these bolts are left handed threads. That would explain a lot in the issue I'm having trying to release the clutch pressure. Any truth to this? The manual doesn't mention anything about this. It only says that the ring gear to differential case bolts are left handed thread. The numbers stamped on the side of the differential case that I believe are a date code. It was made in 05-13-65.

 

[704406]

I don't remember those bolts being left hand thread, only the ring gear bolts for sure ( I had to buy a left hand thread tap) I have an earlier service manual, let me check it tomorrow about the bolts.
I'm sorry to say that I see a lot of black sludge in those pictures, thats an indication of old, burnt fluid,
this might be a good time to replace the clutch pack and make it as good as you can while it's apart.
Those bolts might never have been undone since new, so they will be tight.
And yes that sure grip was made in 1965

 

[704406]

Ok I looked in my 68 A body service manual, it doesn't say the bolts are left hand thread but the sure grip section doesn't really deal with the 8 3/4 only it has the 9 3/4 in it as well.
I'm much more familiar with the 9 3/4 sure grip, I've overhauled quite a few, and it doesn't have left hand thread.
Yukon gear and axle list a bolt for dana 30, 44, & Chrysler 8 3/4 and early gm cars as #YSPBLT-052 left hand thread.
Dana was the OE manufacturer for Chrysler's sure grip, Dana called it Power lock.
Having said that it's likely that it's left hand thread, just wish that I could remember the last 8 3/4 sure grip I did, must be 25 years ago or more now.
Sorry I can't give you a more definite answer but someone on this site should know for sure.

 

[Tirekickertoo]

Update and conclusion... The differential case bolts are indeed “left handed threads”. I proceeded to loosen all eight bolts and was able to move the left/drivers side axle shaft to align the splines. Once aligned, I tightened/torqued to spec. the differential case bolts. After this, the assembly went without issue. 704406, thank you for all the help and suggestions. At this time I’m looking for a vendor for parts to install a new clutch pack. Regards, Tirekickertoo

 

[Tirekickertoo]

Thanks 70446, your reply's and knowledge have been really helpful. I did some searching on the interwebs for a new clutch kit. I'm finding a number of vendors who offer the kit starting around $76.00 and up.

Regards,

Tirekickertoo

 

[Daves69]

Mopar or Dana 60 "Powr-Lok" Clutch Pack


FWIW, and future reference, the last 489 case cone SG I did the ring gear bolts were left hand threads. Everything else was right hand.

 

[Chryco Psycho]

I am glad you got it sorted out , as above it really helps to assemble with the axles slid in first