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Diff difficulties!!!

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nomad

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Could use some input on a problem I seem to be having. My 66 driver with 1275 and 5 speed had to have its original 4.22/1 diff replaced a couple of years ago. Had, I estimate, over a 100K on it. I replaced it with the diff out of my 30K BE. Nice tight early diff [there is a difference].Now the replacement is shot with probably less than 8K on it.

Sooo, is the early diff not as strong as the later? Is the problem something to do with to high a rpm on the diff? [Quite a few 80mph miles]

Appreciate any idea's and BTW, I replaced the entire rear axle at the same time I fitted the BE diff.

I'm planning on more power for this car, are the diff's going to stand up to it?

Tnx,Kurt.
 
Kim; Couple of days ago I thought I felt a vibration and while checking U joints I noticed that the diff housing was hot to the point I nearly burned my hand on it. Pulled the check plug and the oil looked like gold gild paint. Yesterday when I got on it at speed it felt as if I put the brakes on. I'm sure its toast.
Kurt.
 
Did you change the seal and may have overtightened the nut?

Sounds like just bearings. No biggie, change the bearings and cruch sleeve and be on your way. You might not even have to shim it any.
 
Kellysguy: Seal is original and this is the pre crush tube diff so I'm not sure tightness is critical. Correct shims would be.

Kurt.
 
Wondering how these diff's stand up under racing conditions? With the overdrive the pinion would be turning not much below 5000rpm at interstate speeds and I'm wondering If that could have contributed to my problem.

Kurt.
 
Sounds like you may have lost a ring gear carrier bearing. There are two of these bearings in the diff and they often have a sintered bronze ball bearing spacer to evenly space the bearings in the race. These are not too hard to replace, but often require a bearing spreader to pull. The clearance between the outer race and the ring gear carrier/cage housing is just too tight to permit most common bearing puller jaws to engage. If you change the pinion bearings in your old style diff and use the same part numbers, new shims should not be required. You can check and see if the new bearings are the same deminsions as the old.

Most Spridget racers use 3.7, 3.9 or 4.22 gears these days. Not too many 948's running anymore. There may still be some tight tracks that use the 4.55, but not here in the South East Division. But anyway, the engines turn at least 8,000 rpm and do this for 3K feet or better. More at Daytona. The engines cycle up and down between 5K and 8K for up to 21 Laps, or 30 minutes. So, the engine, trany and diff get quite a work out. Most of the time, the racers wear out the teeth on the ring gear or pinion gear. They get worn and hot and break off. Quite a shock in a racing situation. Often leads to collateral damage elsewhere.

Here is my theory assuming a properly set up, but original diff in a mostly unused vehicle. Most of these diffs have set for such a long time that through normal atmospheric condensation, some moisture collected at the contact points where the balls/roller touch the race. Oil has drained off these places. A bit of corrosion occurs and the surface start to erode. This corroded spot creates wear/catch points and the problems starts.

Make sure you use a GL-5 rated oil too.

HTH,
Mike Miller
 
Thanks Mike, that all sounds logical. I've got my shop full of other projects that I hope to get out this week then I'll pull it and see whats up.

Kurt.
 
could it be the oil? i seen to recall the oil for my old ford pu looked just like that it had a simipos rear and had an additive to help lock the clutch pacs on overspin
 
It might just be the bearings. Pull the punkin and give us a look. Those gears are some of the toughest used in anything made. It takes a lot to ruin them in regular driving. I'm thinking the pinion bearings gave it up. Someone could have changed the gears and not knew what they were doing and that pinion depth is critical. I got a set of used 3.90 gears I will sell. They are in good shape. I changed them out to the 3.55 gear set. If that thing was getting hot and not whining like crazy then it must be the bearings and those preloaded pinion bearings are the most likely suspect. Good news is they are cheap at a bearing supply place. Save the shims whatever you do, or you will have to do a lot of measuring and taking the bearings off and on to get the right depth like I did with the new pinion.
 
Thanks folks, I'll repost when I find out exactly what is wrong. I have 4 3.90 sets from a large parts acquisition I made but like the 4.22's since I don't like to shift for hill's. I'll probably just swap in a 3.90 diff which I know a lot of you folks run with the 5sp anyway.
Kim, where do you get a 3.55 set and how available are they? Costly?

Kurt.
 
nomad said:
Thanks folks, I'll repost when I find out exactly what is wrong. I have 4 3.90 sets from a large parts acquisition I made but like the 4.22's since I don't like to shift for hill's. I'll probably just swap in a 3.90 diff which I know a lot of you folks run with the 5sp anyway.
Kim, where do you get a 3.55 set and how available are they? Costly?

Kurt.
Click to expand...
I got mine from Vicky Brit but that was about 7-8 years ago and they have since run out of them(according to others). It cost me about $300 bucks back then but it was a 100% Mowog gear set and fit the cage perfectly right. Maybe hap or someone here knows more about that gear. I heard it was made for the Lotus 7 kits because the car was much lighter and could take the higher gear with the A-series Austin motor. I also heard it was a "daytona" or other big track gear. Otherwise I don't know.
I think it was Spicer or Quaife, one that sold a whole Punkin but they can sell that one to Jay Lenno for his sprite because he is the only one who could afford it.
 
regularman said:
nomad said:
Thanks folks, I'll repost when I find out exactly what is wrong. I have 4 3.90 sets from a large parts acquisition I made but like the 4.22's since I don't like to shift for hill's. I'll probably just swap in a 3.90 diff which I know a lot of you folks run with the 5sp anyway.
Kim, where do you get a 3.55 set and how available are they? Costly?

Kurt.
Click to expand...
but it was a 100% Mowog gear set
Click to expand...

Said, "made in turkey" on the box they came in and yes, NLA. The 3.55 uses the same teeth pattern as the 3.90, but with a 11 tooth pinion instead of 10. The ring gear is the same as the 3.90, just slightly thinner. They came with a shim to go behind the ring gear too. Theoreticly, if you could find a machinist that could make an 11 tooth pinion, you could use the ring gear from a 3.90 set to make 3.55's. I imagine it would be too costly to have that done.
 
Back in the 70's BLMC offered the 3.545 gear to the SCCA crowd to help the 1500's in F-Production keep the rpm's down and engine reliability up. This was especially critical at the long tracks like Daytona and Road America. With 3 main bearings, a very heavy crank, not the best rods and not all that stiff a block, the 1500's had significant higher rpm reliablity issues that the 1296 didn't.

I have some old BLMC Special Tuning literature at home, and it seems to me that the Riley's used the gear as a stock offering.

Not sure if it is a simple pinion tooth count issue. With 11 teeth on the pinion, the pitch on the ring gear might also have to change. BMC through BLMC used a minimum of 8 teeth on the pinion and maxed out at 11. An 8 tooth pinion really looks strange.

Houseman in Canada will cut new ring and pinion gears (and other types). Not a cheap approach, but they do good work and I have set up their gears for an SCCA racer before. SCCA opened the rear gearing ratios a number of years back and this racer had a gear made that fit between the 4.22 and the 4.55. It helped at certain tracks.

HTH,
Mike Miller
 
Mike, I thought it might be a different pattern too, but the 11 tooth meshes right in on the 3.90 ring gear perfectly. It makes manufacturing sense when you think about it, all you really have to do is make another pinion and you have a new ratio.

That's great to know someone will custom cut gears. Any idea on the price?
 
Well, the diff is out and can't see anything wrong without a teardown. Definite binding though. Must be the distance tube on the pinion. There was one heck of a lot of brass in the oil and housing but no steel. Ring gear carrier bearings have brass ball spacer's but they appear to be good. Gears look fine but I have better things to do than try to rebuild a diff right now. Moss shows the part I most likely need as NA anyway [distance tube].

Kurt.
 
Thought of another place where "brass" colored material could come from. There are "belleville-shaped" washers under the spider gears in the center of the differential. Look and see if you lost one of those. Have seen that before too. The best thing to do is to clean the diff up and inspect. Oven cleaner works real well. If it is an old style differential (inspection hole in side of case), then it is un-likely any damage has been done to the distance tube. That thing is pretty simple and straight forward.

The binding might just be collateral from all the material bits thrown about inside the housing. Give it a good cleaning and then an inspection.

What a coincidence with the 10 and 11 tooth pinion fitting the same ring gear. Never checked them myself. Only had the 3.545 diff in my hands once and never thought to check it out to that detail. Great info!

It looks like the Riley's used the 3.727 gear and not the 3.545. Forgot to look last night and see what part number was on the 3.545 from BLMC. If it was an STR number, then it never showed as a production item. They typically would have shown up as an ATA or 8G number. Will see what I find over the weekend. Got an 1098 race engine to finish up over the next few days. Need to check valve to piston clearance and see if I cut deep enough valve reliefs.

Have a great weekend!
Mike
 
Which part is tight, the pinion or the carrier? You have play b/w them so with a little movment you should be able to pinpoint which one.


I'm sure it's more than a coincidence.


STR520
 
Well, I believe I rotated the spider assembley and it was OK but I will check again. The binding is'nt in the bearing's but in the mesh of the gears. Looking again in Moss it shows a shim plus the distance tube on the pinion. I'm thinking that is where the problem is. I can make it turn without binding if I manipulate the drive flange just right. Gearing is precise enough that just a tiny bit of play makes it turn hard.

Well I fitted a 3.9 out of a axle I had. Plenty of oil in the axle and no sign's of leakage so I chanced the seal being OK. Course its not!
I've changed them before so its no biggey just agrevation!

Kurt.
 
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