74 atc 90 axle swap question

[NJPCRX]

I knocked out the rear axle on my 74 ATC-90 and I'm gonna put my later model axle in soon. My new axle has the sprocket pressed on, but I noticed the brake drum off my old axle has different splines. Not gonna work. My question is, do I just need to buy a later model brake drum? Simple as that? The old carrier will work, right? It looked like it should if i it in. What other things will i need? I think my new axle is a 77 or 78.

[Joseph Farrow]

Correct you just need the later style brake set up.

[NJPCRX]

Just the part that presses on the axle? The other pieces like the shoes and cover still should fit?

[90guy]

If you grab the new axle with more splines. You need to grab the brake drum to match that axles splines. Also would need new hubs for hte more splines also. Pretty straight forward if you have the new style drum.

[ps2fixer]

I already sold my 78 brake drum, but I have a pair of hubs yet on my store. I don't think you need anything else for the conversion, however, I do have the brake drum cover and backing plate as well. I have a fair collection of 110 parts (not listed on my site) that might interchange if you can't locate a brake drum.

http://atcfixer.com/index.php?main_p...&products_id=1

Let me know if you are interested, Thanks!

atcfixer/ps2fixer

[HairyJR]

Just checked my current survivor '74 Daytona project rear axle and the '70 US90 survivor project I completed back a couple months, at the least you need to replace the bearing carrier oil seals, the newer axle and brake drum seal fits are larger 42mm as opposed to the originals at 40mm. Next would be the protective sheet metal for drive chain and brake drum will also need replaced, inner and outer, not an issue if not being used.

"HJ"

[NJPCRX]

Are you sure HairyJR? I have never heard of this before. I thought the axle was a direct replacement if I it in the carrier? I bought a new brake drum with more teeth and I assume the old drum cover will fit over it? And I got a new style cover plate for the chain guard since the sprocket bolts are different. The old hubs off my Banshee were a perfect fit on the new axle, and I'm using an old set of warrior wheels on the hubs. Its kinda narrow. I might have to get some widened hubs.

[ps2fixer]

It don't seem like having to something together is a proper fit. If only the seals are different, then ing them in would probably damage them. I'm not an expert on the matter though.

I know I have a carrier from a 78 atc90 though if that is needed. Not trying to bomb this thread with parts, just offering them up so you don't have to go and search for a source of the parts.

[HairyJR]

NJPCRX, I'm a retired machinist by trade, and don't comment on the forum that often, although I lurk several times daily. Before I commented I actually pulled the axles out of the two junker '74 frames I have just to double check, didn't want to give wrong info. Yes a will drive the axle in but your axle won't spin as free as it should. There are several styles of drive chain sheet metal covers so I won't comment which '75 or newer model to use, but doesn't change the fact the original inner sheet metal next to your carrier seals are too small.

Take ps2fixer up on his offer as his carrier seals are correct.

"HJ" back too

[ps2fixer]

Good and bad news from me, looks like I sold the 78 atc90 rear bearing carrier.

For 100% exact interchange, the rear bearing carrier is from 76-78 based on the part number of mine (not sure why it is labeled as a hub).
http://www.partzilla.com/parts/detai...1-918-070.html

Deeper research shows 1974s were 40mm seals as well as 1976-78.

76-78 -> http://www.partzilla.com/parts/detai...3-918-015.html

74 -> (item 25) http://www.gearhead.com/oem-parts.ht...ATC90K2-JPN-A/

Bearings are the same part number too, and finally the housing is the same part number, so if the diagram is correct from gearhead.com, the axle should slide in just fine, and the seals will be the right size. You should NOT have to it though, clean off any rust, and put some grease on it to help it slide easier.

I didn't research if the backing plates are any different, but I suspect they would be the same, or similar enough not to cause problems, the brake cover I'm not sure on since it is a bit of a different design, let me know and I'll dig into that as well if you want me to.


Double check my work if you want, and if i'm wrong, feel free to correct me so this thread stays accurate (links would be great or at least part numbers).