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Author Topic: Quick & Cheap Belarus 420A/T40A fwd Slip Clutch Installation  (Read 3068 times)

imperial1960

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Re: Quick & Cheap Belarus 420A/T40A fwd Slip Clutch Installation
« Reply #3 on: March 26, 2017, 01:46:57 PM »
Great story pictures are nice you have a nice setup!
Belarus 562 4x4 russian loader bucket

cowrider

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Re: Quick & Cheap Belarus 420A/T40A fwd Slip Clutch Installation
« Reply #2 on: March 26, 2017, 10:55:18 AM »
Thanks for posting this as well as the pictures. Always nice to have information and ideas flowing.

Brought Upright

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Quick & Cheap Belarus 420A/T40A fwd Slip Clutch Installation
« Reply #1 on: March 25, 2017, 08:03:43 AM »
An EF1 tornado recently flattened part of our New England property and there's a lot of big trees to clean up so I installed a slip clutch to protect the front wheel drive system from heavy loader use.

IMHO Belarus 400-series 4x4 tractors (420A, 420 AN, 425A, 425AN, T42LB, T40A, T40AM) , seeing heavy loader use or not, require a slip clutch on the fwd driveshaft if you don't want trashed u-joint yokes, front diff input shafts & driveshafts etc.

Some folks remove the fwd driveshaft before (or after!) they break something but personally, I NEED four wheel drive on these steep hillsides etc. Even with 1280 + lb drawbar ballast, good tires & locking the diff I can't make some muddy/icy/snowy grades without fwd, let alone when skidding big logs etc.

A 420A slip clutch installation should take less than half a day to make & only costs about $100 in materials. Note that most of the following part lengths aren't critical, I'm just relating the quick & cheap way that worked for me. Keep in mind that the stock 420A/T40A driveshaft is about 39-1/2" long but, since the front diff input shaft floats fore & aft, custom driveshafts up to 40-1/4" long can be used.

MATERIALS:
-1) 7" dia. adjustable slip clutch rated for at least 50 hp with 1-3/8" round shaft "smooth" both sides (no splines) & pre-drilled for 1/2" shearbolts. I bought one for $66.50 +shipping from ag_medic on eBay (Brooks AG Parts, New Richmond, OH). This slip clutch is adjustable anywhere between 20hp   (2335 Lbs. Torque) and 55hp (6419 Lbs. Torque) & comes with two 1/2" x 3" grade 8 bolts, lockwashers & nuts but you'll also need at a 1/2" x 3" grade 2 shearbolt.

-1) Mild Steel A513 TYPE 5 DOM Tube 1.375" OD  x 1.185" ID x 12" $4.09 @ OnlineMetals. [I have a 30mm dia OEM driveshaft (Part #: Т40А-2302072) but match the tube ID to your driveshaft if it's different];

1) Mild Steel A513 TYPE 5 DOM Tube 2" OD x 1.375" ID x 12" $24.52 @ OnlineMetals. (actually only 10" is needed).

TOOLS:
-Basically just a metal cutting chop/band saw (or hacksaw in a pinch), drill press, 1/2" drill bit, file & orbital sander w/120 grit sandpaper (or a lathe). Welding is unnecessary.

FABRICATION:
-Layout & cut the driveshaft so your slip clutch fits under the rear high point of oil pan just before the bell housing (see pics). My slip clutch cleared the oil pan by about 3/8" & you only lose less than 3" of ground clearance. The 2" OD tubing clears the tranny by 9/16" and there's room to pull the tranny drain plug;

-Cut driveshaft 26-7/8" from one inner flange face;

--Cut other driveshaft section to 7" from inner flange face;

-Cut the 12" long 1.375" OD "spacer" tube to 6-7/8" long and turn or file/sand the two driveshaft ends for snug press-fit & install flush, the 6-7/8" long section on the rear (short) driveshaft section & the remaining approx. 5" long section on the front (long) driveshaft section. (If hand fitting the short driveshaft section it's handy to attach the two driveshaft sections by bolting the flanges together face to face to enable vise clamping).

--Cut the 2" OD tube to 10" long;

-Sand/turn the 1.375" OD "spacer" tube [now mounted on rear (short) driveshaft section] for a snug press-fit with 2" ID tube. If you don't have a lathe roll your bolted-together driveshaft sections on floor or workbench while orbital sanding to fit then press on the 2" OD tube stopping 3/4" from inner flange face for flange bolt installation clearance;

-Press clutch onto long driveshaft section until it bottoms out at 3-1/2" & drill 1/2" shearbolt hole. Bolt clutch on to long driveshaft section with 1/2" x 3" grade 2 shearbolt. (You can grind/cut notches in the grade 2 shearbolt here for extra protection if your clutch freezes up etc...loosen springs & "burn in" clutch after dormancy to make sure it isn't rusted/bound up);

-Drill the 2" OD shaft 1-1/2" from forward end for clutch rear 1/2" bolt & drill 3-1/2" from flange face of rear (short) driveshaft section for 1/2" bolt. (I used an additional 1/2" bolt to attach the 2" OD & 1.375" OD tube to the short driveshaft section but one will work);

-Bolt 2" OD tube to short driveshaft section with 1/2" x 3" grade 8 bolt;

-Fit the 1-3/8" OD male clutch shaft to the 1-3/8" ID x 2" OD heavywall tube. (Again, if you don't have a lathe roll your bolted-together clutch/driveshaft unit on floor or workbench while orbital sanding shaft to fit). After fitting, the 1-3/8" OD male clutch shaft should extend 3-1/4" into this 2" OD heavywall tube. Bolt together with 1/2" x 3" grade 8 bolt.

-Adjust your slip clutch spring tension: The "50 HP/5835 Lbs. Torque" setting (26mm spring length) absorbs torque spikes on my 420A without slipping excessively but you may want to start at the lowest setting (20 HP) & work your way up marking your clutch disc & housing to monitor slippage;

-Check the four ft diff bolts for tightness & bolt the driveshaft/clutch assy in tractor with 12 flange bolts & put that 4x4 beast back to work!

BTW, Belarus informed me that their 500 series tractors & up have fwd slip clutches.
« Last Edit: December 18, 2017, 09:16:23 PM by Brought Upright »
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