Drive shaft conundrum

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The whole procedure went pretty smoothly. Unfortunately I didn't have a low scale in-lbs torque wrench so the pre-load torque may not have been that accurate. It was taking about 10 in-lbs to turn, but the needle will fluctuate approximately +/- 2 which made it hard to match one torque. I tried to match this same torque after tightening the nut.

Another question I have now is in regards to the o-ring for the pinion's bearing carrier. The o-ring I removed had a circular cross-section, and the replacement had a square cross-section. Any thoughts on this?

 

Bentworker

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I wouldn’t worry much about the cross section of the o-ring as long as it wasn’t so large that it would expand beyond the groove when clamped and spread out onto the flat surface that should be metal to metal. You could take a straight edge and depress the o-ring flush in the groove in one spot just to be sure

 
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After measuring, the shaft would have to be 1" longer due to switching to the short yoke, which makes sense since that's what the theoretical length difference is. The shaft length will have to be 51 1/8". I received a quote from Strange for $330 for a 3" chromemoly shaft. The other quote I had was for more, but it was a 3.5" shaft. The 3" shaft has a 80% critical speed value of 6,000 rpm. The only way I can see turning the shaft that fast would be in a dyno session. The actual critical speed would be 7,500 rpm so I don't think that a one time short burst to 6,500 rpm in a dyno session will matter.

 
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I ended up ordering a 3" Chrome Moly steel driveshaft from Strange w/ 1350 u-joints. The driveshaft is 51 1/8" long center-to-center. I will paint it black since it comes raw.

I hope my measurements were right. I will be testing it soon.



 
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boilermaster

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Hi Tony,

Kind of watching this thread, as I am in a somewhat similar situation.

have the 408 stroker, which is supposed to deliver around 500 lb. ft. of torque.

I am using a toploader out of my 73 q code and a 9'' with 3..50 gears and clutch type locker.

Already I have concerns about the stock 28 spline axles and the sb toploader input shaft.

the rear diff will need 31 spline axles.

I am having a hard time trying to find just side gears and adjusters to switch to 31 spline without replacing the whole locker..

Can you tell me just what specific tko 600 you chose and why.

What 1st. gear ratio and od ratio ?

What input spline and clutch disc ?

I already have a very good 11'' clutch and bell housing for z bar linkage.

what axle ratio do you plan to use and tire size ?

Boilermaster

 
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Hi Tony,

Kind of watching this thread, as I am in a somewhat similar situation.

have the 408 stroker, which is supposed to deliver around 500 lb. ft. of torque.

I am using a toploader out of my 73 q code and a 9'' with 3..50 gears and clutch type locker.

Already I have concerns about the stock 28 spline axles and the sb toploader input shaft.

the rear diff will need 31 spline axles.

I am having a hard time trying to find just side gears and adjusters to switch to 31 spline without replacing the whole locker..

Can you tell me just what specific tko 600 you chose and why.

What 1st. gear ratio and od ratio ?

What input spline and clutch disc ?

I already have a very good 11'' clutch and bell housing for z bar linkage.

what axle ratio do you plan to use and tire size ?

Boilermaster
Let me answer your questions as best as I can:

  • We are working with similar numbers of power. I should be in the 500 lb.ft range as well.
  • I have the TCET5008 with 0.64:1 overdrive and 2.87:1 for 1st gear. There were two options and I chose the one with the most overdrive.
  • The input splines are 26, which is standard for the TKO. I am using the 10.5" kevlar/organic clutch from Modern Drivelines.
  • Right now my axle ratio is 3.00 but the plan is to bump it up to 3.50 and upgrade to 31 spline axles. The tires are 26.6" in diameter.

I hope this helps.

 
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boilermaster

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tony,

I HAD 370 gears when I swapped out the c4 transmission that the p.o. had in there.

I did not care for the .370 with the toploader and I was using bfg 255 60 r 15 tires.

you may like it with that overdrive ratio.

do you intend to make this combination hook up ? , just wondering , you stated how tall your tires were but not brand or aspect ratio.

I will say this: before I switched to the nitto 275/ 60r15 my bfg's would not hook until I was tached out in second gear. first gear was much worse.

great tires for croud pleasers but not very good for going straight and fast.

still contemplating my nest move before I actually break something.

Boilermaster

 
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tony,

I HAD 370 gears when I swapped out the c4 transmission that the p.o. had in there.

I did not care for the .370 with the toploader and I was using bfg 255 60 r 15 tires.

you may like it with that overdrive ratio.

do you intend to make this combination hook up ? , just wondering , you stated how tall your tires were but not brand or aspect ratio.

I will say this: before I switched to the nitto 275/ 60r15 my bfg's would not hook until I was tached out in second gear. first gear was much worse.

great tires for croud pleasers but not very good for going straight and fast.

still contemplating my nest move before I actually break something.

Boilermaster
My tires are BFG 295/50R15. The end intention will be to get as much as hook up as possible but I understand that with that much of a torque it will be hard. When I upgrade the rear end I will install a TrueLocker to help. Once all is upgraded I am expecting to be very beefy. The next weakest point will be the springs which eventually will be upgraded to a 4.5 leaf package.

What Nitto tires do you have? My BFG are only one year old but I will consider an upgrade once they are worn (maybe in a couple weeks :whistling: ). Going to 17s won't be out of the question at some point. The selection is much more wide at 17" than 15".

 

boilermaster

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Tony,

I am using Nitto 555r tires

275/60 R15 @ 27.76'' they are classified as a drag radial and are only a 15K mile tire.

they should not dry rot.

100% better hookup than the 255/60 r 15 bfg's I was using.

Also using tinmans subframe connectore and underride traction bars.

car goes straight with zero wheel hop.

Just a side note, I also switched to staggered rear shocks, massive wheel hop before I did that.

Boilermaster

 
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Tony,

I am using Nitto 555r tires

275/60 R15 @ 27.76'' they are classified as a drag radial and are only a 15K mile tire.

they should not dry rot.

100% better hookup than the 255/60 r 15 bfg's I was using.

Also using tinmans subframe connectore and underride traction bars.

car goes straight with zero wheel hop.

Just a side note, I also switched to staggered rear shocks, massive wheel hop before I did that.

Boilermaster
For now I am stuck to the BFG but will consider those in the future. I also have Tinmans subframe connectors and staggered shocks. I don't have traction bars since I am waiting until I can drive the car and feel it before I start throwing $$$ in suspension upgrades. But, for sure, upgrades are to come.

 
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Hi Tony,

Kind of watching this thread, as I am in a somewhat similar situation.

have the 408 stroker, which is supposed to deliver around 500 lb. ft. of torque.

I am using a toploader out of my 73 q code and a 9'' with 3..50 gears and clutch type locker.

Already I have concerns about the stock 28 spline axles and the sb toploader input shaft.

the rear diff will need 31 spline axles.

I am having a hard time trying to find just side gears and adjusters to switch to 31 spline without replacing the whole locker..

Can you tell me just what specific tko 600 you chose and why.

What 1st. gear ratio and od ratio ?

What input spline and clutch disc ?

I already have a very good 11'' clutch and bell housing for z bar linkage.

what axle ratio do you plan to use and tire size ?

Boilermaster
Now I am curious since I am thinking of going with 3.50 gears and a Trueloc. What is your 1st gear ratio? Can you spin the tires in 1st gear without clutch help? What about 2nd gear?

I can spin my tire in 1st gear very easily without clutch help with my current open differential setup. In 2nd gear I can also spin w/o clutch but not as easy.

 

73' mach 1

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My 408 will be similar to most in this post. I've yet to get my setup together but I believe all the TKO 600's have the same 1st-4th gear ratio. The TKO 500 has a different 1st. After that it's about the OD. Mine is a .64 and I currently have 3:89's. I've been reading a lot about how I might have be better with the .82 but it's all about trade offs and where you think you'll spend most of your time with regards to MPH. Where I live most roads are 45MPH. I'll be spending most of my time in 4th gear but know when I get on the highway it will be nice to not have the engine screaming. If I decided to back off my gears for the sake of a better 1st gear it would significantly effect my 5th gear. To help my 1st gear I plan to go with at least a 28" tall tire on either a 17-18" rim. I already have traction bars, sub-frame connectors, bils sport shocks and 4.5 mid eye leaf springs. All that combined with a nice DR tire should help keep it straight and to the ground.

 

boilermaster

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My 408 will be similar to most in this post. I've yet to get my setup together but I believe all the TKO 600's have the same 1st-4th gear ratio. The TKO 500 has a different 1st. After that it's about the OD. Mine is a .64 and I currently have 3:89's. I've been reading a lot about how I might have be better with the .82 but it's all about trade offs and where you think you'll spend most of your time with regards to MPH. Where I live most roads are 45MPH. I'll be spending most of my time in 4th gear but know when I get on the highway it will be nice to not have the engine screaming. If I decided to back off my gears for the sake of a better 1st gear it would significantly effect my 5th gear. To help my 1st gear I plan to go with at least a 28" tall tire on either a 17-18" rim. I already have traction bars, sub-frame connectors, bils sport shocks and 4.5 mid eye leaf springs. All that combined with a nice DR tire should help keep it straight and to the ground.
73'mach1,

Hope you have some strong 31 spline axles, guessing that a 17 or 18'' wheel and in the range of 28'' tall is going to mean a 45 aspect ratio tire.

That will put a lot of stress on your axles if you intend to hook up and like to play.

I am in a similar situation, but have 275/60r15 nitto drag radials.

It definitely hooks up, but I still have 28 spline axles and a small block toploader.

So I will at least convert to aftermarket 31 spline axles this winter, still debating what to do with transmission.

Have you done any overall ratio calculations with respect to a 27 or 28'' tire as of yet ?

Boilermaster

 
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Related to my original topic I must confess that I screwed up. If you remember I replaced the pinion yoke of my current differential so I can fit the new driveshaft. This was a temporary measure until I get my new center section with Trueloc 3.5 gears and 31 splines. I placed a lot of attention into making sure I retorqued the pinion shaft correctly following the instructions in this thread. Now, for some reason that I can't still figure out, I did not completely refill the axle. I remember clearly refilling it using 1.4 quarts of oil (I had not emptied it all since I only removed the pinion carrier). I filled it until oil came out of the plug. I tightened the plug and went about. Driving the car this weekend I started hearing a grinding noise in deceleration. I figured it was the differential so I started driving back home trying to not decelerate with the engine. After inspecting, the noise was definitely coming from the pinion carrier. Turning the pinion in "reverse" was also tight and you could hear/feel the grinding. When I checked the oil I found out it was well below the plug level - I was not able to touch any fluid with my finger. I filled the axle with the reminder of the oil bottle and I was able to get 0.6 quarts more on it before fluid started leaking through the hole. All in all, I realized I screwed up and for some reason that I can't explain I didn't fill the axle housing completely. The bad news is that the car is out for the year, which may have been just a couple more weeks until the snow. The good news is that I was already planing on replacing the center section so no "unplanned" expenses to worry about.

 

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That is strange. No sign of gear lube on the inside of the wheels or tires?

 
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That is strange. No sign of gear lube on the inside of the wheels or tires?
Nope. No leakage. I have two theories. One is that the hose may have come out slightly and pour on the threads, which could cause oil to leak out of the plug. Although I don't remember the details when I did it, I expect I would have noticed. The other, which I don't know if it is possible in an axle, but happened to me in a boat's lower unit, is that an air gap can be left inside that would make you think you are full. In insight, I should have turned the pinion and double checked.

 
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