Rear end disassembled - Help a stick axle novice (various questions)

[Cobra4B]

Pulled the 3rd member to inspect everything and paint it and the axle housing. This sick axle stuff is all new to me so any info provided is much appreciated.



1. Does this wear pattern look normal? When the last engine was installed (347) we went back to 3.50 gears and had the 3.89s removed to keep the RPMs around 6000. These have very little run time. They don't make any noise.




2. What's the torque spec on the nuts that hold the 3rd member in place and on these bolts that hold the pinion cover/support in place?



3. Is this an excessive amount of fluid/grease on the driver's side axle (left one)? The inner seals appear new from the aforementioned gear swap.





4. The inner splines on the passenger side axle have more wear than the driver's side. Is this excessive? The driver's side still have a "flat top" whereas the passenger side look sharper.



5. Is it OK to weld on the axle housing? Is it easy to warp? The weld at the top has been seeping and was "repaired" with RTV.



6. Are the rear caliper mount flanges supposed to be slightly angled, or square to the axle tube? Both are angled outward slightly.

Driver


Passenger


7. Any other advice or tips while I have this apart? Any big "don't do that" itmes? I.e. I have the 3rd member bagged and sitting on my work bench on a towel. Obviously keeping the gears etc. clean is good, and I'll clean them before re-installing the 3rd member, but is it something where I need to be careful handling them and keep them spotless? Anything else? I took care removing and re-installing the axles so as to not dislodge the inner seals.

Thanks,

Brian

[Cobra4B]

Figured I'd share John Leverett's (Panoz Dir. of Engineering/R&D) response to my questions.

Originally Posted by John Leverett

Brian,

It is hard to tell from the picture since the reflections can be tricky. The pinion depth looks good but I can't tell if I am also seeing a ridge. Take a look at the attached image and if that is a ridge where the green arrow is pointing, then the backlash is way off due to the side spacing of the Ring. If it is not a ridge and just where the tooth contact stops, then you are fine.

As far as the other items on your post:

#2 Should be about 45 ft-lbs.

#3 Is it diff fluid or grease? It looks like grease but either way the axle should be dry in the middle. If it is grease, your rear hub bearing seal is going out, if its diff fluid, then your axle seal is failing. I suspect it is the rear hub bearing seal.

#4 The axle with the "sharp" splines has a lot of wear! It's time to replace it and relegate it to emergency spare status.

#5 It is Ok to weld on the axle housing. Warpage is an issue only when you weld out on the ends where it can result in an unintentionally cambered or toed axle housing if not done correctly.

#6 The rear caliper flanges are supposed to be square. I suspect all the years and use have caused your mounts to fatigue. Don't forget some of these cars are 15 years old now and have a lot of hours on them. I would suggest straightening them out and adding a gusset.

Hope that helps.

Best Regards,

John M. Leverett
Dir. of Engineering/R&D
Panoz Auto Development Co.

[NZGTRA17]

Originally Posted by Cobra4B

Figured I'd share John Leverett's (Panoz Dir. of Engineering/R&D) response to my questions.

Cheers Brian. Is that a gasket I can see on the diff center? If so, we dont use a gasket and just use a good adhesive sealant like "Wurth Silicone Special 250". Using gaskets I have had the center work loose during a race. Using just adhesive sealant this has never happened. My diff guy makes a living doing race rear ends and he swears by using the Wurth product instead of a gasket.

Kel.

[Cobra4B]

Yeah it was some kind of fiber based gasket and RTV sealant. I've read how-to's which mostly say to use gasket-maker only.

[bbenavitz]

Cobra4b, great post, very thorough on your part with all the pics and I appreciate the insightful response from PAD. I just had the third member on my GTWC out due to a leaking gasket. I learned a lot about the rear end of these cars but now I know more of what to look for. Unfortunately, I did not look for wear patterns on the ring gear or the axel splines :-( but now I know.

[NewToPanozGTS]

Originally Posted by bbenavitz

Cobra4b, great post, very thorough on your part with all the pics and I appreciate the insightful response from PAD. I just had the third member on my GTWC out due to a leaking gasket. I learned a lot about the rear end of these cars but now I know more of what to look for. Unfortunately, I did not look for wear patterns on the ring gear or the axel splines :-( but now I know.

Lots of good info here guys, thanks.

Question: What's the conventional wisdom on the need for a rear end oil cooler? My GTS has one but it appears that the GT-RA's do not. I never ran one on my vintage car and never had any issues after I switched to an all gear TruTrac - which is what Panoz put in our cars. I'd like to shed the weight but not the reliability.

[Cobra4B]

Never had an issue with our car, but don't run more than 45 minutes to an hour max. Car has lots of air flow up under it. My Corvette has the trans/rear tucked up in the chassis and gets poor airflow. It needs a trans cooler (which I have yet to add) but not really a diff cooler. When running in the summer I get a high trans temp warning after about 35-40 minutes. I usually run the last five minutes with the trans light on!

[NZGTRA17]

Originally Posted by NewToPanozGTS

Lots of good info here guys, thanks.

Question: What's the conventional wisdom on the need for a rear end oil cooler? My GTS has one but it appears that the GT-RA's do not. I never ran one on my vintage car and never had any issues after I switched to an all gear TruTrac - which is what Panoz put in our cars. I'd like to shed the weight but not the reliability.

This really comes down to what rear end ratio you run (steeper gears make more heat due gear speeds) how long you run the car for continuous (per Brians response), how much hp you have and what other mods you have done (particularly that would affect airflow around the rear end).

My car was fine without a cooler running up to 6 hours continuous when we had around 400RWHP. After fitting an undertray which reduced airflow to the rear end dramatically we now discolour the oil badly after a 1 hour race, particularly now we have 500+RWHP.

I have just purchased a NASCAR 2 stage external pump setup and will be fitting this to cool both the diff and gearbox.

In short, if things look good now but you really really want to lose weight, I would try dropping the belt off the pump, run the car but keep an eye on the oil colouration. If you are hurting the oil that will tell you where you sit. If it doesnt work you only have to refit the belt.

I am changing out the oil (Redline heavy shock proof) on my rear after every 1.5 hours at present until the pump and cooler are fitted.

Kel.

[Panoz60]

Additionally, I would strongly suggest running only synthetic fluids; not only on the rear differential, but the gear box, engine, and synthetic grease on axle bearings. I was fortunate to sit in on a seminar a few years ago at the PRI (Performance Racing Industries) Show in Orlando. The instructor was an engineer from Ganassi and made me a believer.

Also (and I am not trying to sell MY stuff) but there is a ceramic based dry-film treatment that can be applied to the ring gear and pinion. Not only is it self lubricating, but it also holds a small amount of fluid to the gear surface. We have applied this to countless gear sets for every type of racing. The gears show little to no wear after a full season of abuse. I would suggest checking locally where you are to see if there is a shop that applies dry-film. We charge $75 a gear set. I can not imagine a applicator in your area would charge much more than that.