8430 2 speed

I have a 1978 john deere 8430 articulated tractor that has blown the 2 speed. Is it possible to replace a straight cut gear with a helical cut gear unit. If so does anything other than the 2 speed unit need replaced.

I am pretty sure that when our 2 speed was done on our 8430 it was just a matter of changing to the helical cut gears and a couple of other modifications versus buying a whole new assembly.

Yes you can replace the complete unit with the helical cut newer one,,you will feel a slight difference in the speed..and it is not a bad job to change out, you turn it to the right and remove the rear bearing quill housing /drive shaft and there are 5 Allen headed bolts holding it in place, it is a bit of a Utrecht to get your hand back in there to feel for the bolts..I would check with a salvage yard for one out of an 84/8640-50..

Hi-Lo Planetary Replacement Kit
Cart key PART NO. PART NAME QTY SERIAL NO. REMARKS
1 R57050 O-Ring 1
2 R57047 Cap Screw 5
3 F2741R Packing 1
4 R60038 Packing 1
5 R62842 Spring 1
6 RE12772 High-Low Clutch 1 (SUB FOR AR82370, AR97024 OR RE1 0769) (SUB RE12773, F2741R, (5) R 57047, R57050, R60038 AND R62842)
RE12773 High-Low Clutch 1 (ALSO ORDER F2741R, (5) R5704 7, R57050, R60038 AND R62842)

Or

Hi-Lo Clutch Disks And Low Range Pinion Replacement Kit
Cart key PART NO. PART NAME QTY SERIAL NO. REMARKS
1 F2741R Packing 1
2 R60038 Packing 2
3 R57047 Cap Screw 5
4 R57558 Packing 1
5 R59137 Washer 1
6 R79831 Piston 1
7 R39322 Ring 2
8 R50349 Washer 1
9 R50222 Bushing 1
10 R38295 Needle Roller 3
Cart key PART NO. PART NAME QTY SERIAL NO. REMARKS
11 AR68324 Drum 1 MARKED R57044
12 R39304 Washer 1
13 R57046 Washer 1
14 R57045 Piston 1
15 R50348 Disk Spring 8
16 R39299 Snap Ring 1
17 RE29816 Disk 7 SUB FOR AR71561
18 R39259 Clutch Plate 8
19 R50604 Spring 6
20 R50152 Plate 4
Cart key PART NO. PART NAME QTY SERIAL NO. REMARKS
21 RE29815 Disk 4 SUB FOR AR71560
22 R50153 Plate 1 ORDER R59467
R59467 Plate 1
23 R30165 Cap Screw 6
24 R33083 Washer 2
25 AR90973 Pinion 1 LOW RANGE SUN; SUB FOR R57099
26 R57050 O-Ring 1
27 AR92554 Disk 1 ORDER COMPONENTS

Last quad pack I removed was a 8450 that had burned-up the planet carrier and gears. Wasn't economically repairable.

A Deere reman unit was like $5000!...Abilene Machine had none in stock....All State Ag Parts had one in Missouri for like $2500 rebuilt ready to go. I put the 'core' back together nice and neat and had the customer ship it back for the $500 core and installed a $2000 reman two-speed.

Buying the parts and gears and even with a used planetary carrier and used gears would've cost way more than $2500....approaching JD's cost for a reman unit.

So unless the big parts are reusable....probably more economical to check Abilene or All State for availability.

Failure causes? Where those two speeds undersized , had oiling problems or what ?

I always thought the two-speeds in the 4 wheel drive 30/40/50 series appeared to be about the same size as the two wheel drive tractors. In reality I'm sure they were beefed-up to some degree.

There is a bushing in the end of the crankshaft that can wear-out and loose lube pressure....clutch pumps can go bad..in which case the tractor usually just stops....pto clutch can shuck the fibre facings and plug the clutch housing sump screen....sometimes the quad pack just wears out...shift linkage can get out of adjustment and not allow the two-speed/quad pack to shift completely....water in the oil will strip off the facings on the brake/clutch discs/syncro discs throughout the tractor...lots of things can go wrong with an old JD field mule!

Deere claimed that the vibration of the straight cut gears was the main issue,,the new helical cut gear unit was better.I was involved with a lot of these back when they were new, and I have rebuilt a lot of them, but it is not economical now..

Tims, from the back you can acess to the gears and the disks, or only the gears?

From the back the complete unit comes out in one piece,,you will skin a couple knuckles when you do it..remove the 5 Allen head bolts, a skinny hand run flat in over the top will let you find them,make sure your socket is on tight, I use to have one welded onto an extension,, then you need to twist it a bit as it comes out, it will weigh about 30lbs.

Thanks everyone i ordered a used unit today and new shaft today. The carrier exploded and clutches are burnt. Pretty sure this started last fall when it got ran low on oil after a hose blew when being ran at night and pumped most of the oil out i guess. Not one running it at time