{"id":4504,"date":"2026-10-26T08:54:44","date_gmt":"2026-10-26T08:54:44","guid":{"rendered":"https:\/\/www.hongtengdaparts.com\/product\/caterpillar-455-7978-piston-pump-428f2\/"},"modified":"2026-10-26T08:54:44","modified_gmt":"2026-10-26T08:54:44","slug":"caterpillar-455-7978-piston-pump-428f2","status":"publish","type":"product","link":"https:\/\/www.hongtengdaparts.com\/tr\/product\/caterpillar-455-7978-piston-pump-428f2\/","title":{"rendered":"455-7978 Variable Piston Pump for CAT 427F2 428F2 434F2 Backhoe"},"content":{"rendered":"<p>Caterpillar&#8217;s title for this part states the construction and the control behaviour in one line: variable displacement piston pump. That is the most explicit designation in the backhoe pump family we have published, and it sets the diagnosis for a machine that has lost speed rather than lost power.<\/p>\n<h2>Applicability<\/h2>\n<p>CAT 427F2 with the C3.4 engine from machine prefix HWK 00001, 428F2 with the C4.4 at LYG and HWN, and 434F2 with the C4.4 at LYK and HWR. The F2 generation is a distinct parts set from the earlier F series, whose main pump is <a href=\"https:\/\/www.hongtengdaparts.com\/tr\/urun\/caterpillar-307-3063-main-pump-422f\/\">307-3063<\/a>. Do not treat the two as interchangeable on the strength of a similar mounting face.<\/p>\n<h2>What variable displacement means for diagnosis<\/h2>\n<p>A variable pump changes its output against a control signal. Two different faults therefore produce the same complaint of slow functions:<\/p>\n<ul>\n<li><strong>The pump cannot reach full stroke.<\/strong> Internal wear, a sticking control, or a compensator set wrong. Flow is short at high demand but reasonable at low demand.<\/li>\n<li><strong>The pump is never commanded to full stroke.<\/strong> Pilot pressure, linkage or electronics. The pump is healthy and the machine is not asking for output.<\/li>\n<\/ul>\n<p>The distinction decides whether you buy a pump or a valve. Measure pressure and flow at working temperature while watching the control response, and work through our <a href=\"https:\/\/www.hongtengdaparts.com\/tr\/ekskavator-ana-pompa-regulatoru-teshis-ayari\/\">regulator diagnosis and adjustment guide<\/a> before ordering. The <a href=\"https:\/\/www.hongtengdaparts.com\/tr\/ekskavator-hidrolik-pompasi-alicilari-teknik-sartname-rehberi\/\">pump buyer&#8217;s and specification guide<\/a> covers how to compare a replacement against the original specification, including control type and rotation.<\/p>\n<h2>Fitting<\/h2>\n<p>Match shaft spline, pilot diameter, flange, port positions and control orientation against the removed pump. Prime the casing with clean oil before the first crank. Fit a new return filter element and clear the suction strainer, targeting ISO 4406 18\/16\/13 for the piston components in the circuit. Keep the case drain unrestricted to tank, within the published 0.1 MPa normal and 0.4 MPa peak limits. Confirm rotation, then prove pressure and flow and record both.<\/p>\n<h2>Ordering<\/h2>\n<p>Send the number from your old pump and the machine serial prefix. Minimum order one piece. New aftermarket units carry a three to six month warranty as stated on your proforma invoice. Bench tested, photographed against your order before the wooden case closes, delivery 5 to 8 working days from payment subject to stock. The range sits under <a href=\"https:\/\/www.hongtengdaparts.com\/tr\/urun-kategori\/ekskavator-hi%cc%87droli%cc%87k-pompasi\/kedi-hidrolik-pompasi\/\">CAT hydraulic pump<\/a>, ve <a href=\"https:\/\/www.hongtengdaparts.com\/tr\/ekskavator-hidrolik-pompa-kece-seti\/\">the seal kit rebuild checklist<\/a> explains what a proper hydraulic repair should include.<\/p>","protected":false},"excerpt":{"rendered":"<p><strong>Part:<\/strong> 455-7978 variable displacement piston pump for CAT 427F2, 428F2 and 434F2 backhoe loaders, listed by Caterpillar as a Variable Displacement Piston Pump.<\/p>\n<p><strong>Role:<\/strong> main hydraulic pump for the implement circuits, not a fan pump.<\/p>\n<p><strong>Supplied as:<\/strong> new HTD-brand replacement, made in China. MOQ 1 piece, wooden case, dispatch 5 to 8 working days.<\/p>","protected":false},"featured_media":4486,"template":"","meta":[],"product_brand":[],"product_cat":[70,46],"product_tag":[713,714,715,54,702],"class_list":["post-4504","product","type-product","status-publish","has-post-thumbnail","product_cat-cat-hydraulic-pump","product_cat-excavator-hydraulic-pump","product_tag-455-7978","product_tag-cat-428f2","product_tag-cat-434f2","product_tag-caterpillar","product_tag-main-pump","first","instock","shipping-taxable","product-type-simple"],"_links":{"self":[{"href":"https:\/\/www.hongtengdaparts.com\/tr\/wp-json\/wp\/v2\/product\/4504","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.hongtengdaparts.com\/tr\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/www.hongtengdaparts.com\/tr\/wp-json\/wp\/v2\/types\/product"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.hongtengdaparts.com\/tr\/wp-json\/wp\/v2\/media\/4486"}],"wp:attachment":[{"href":"https:\/\/www.hongtengdaparts.com\/tr\/wp-json\/wp\/v2\/media?parent=4504"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/www.hongtengdaparts.com\/tr\/wp-json\/wp\/v2\/product_brand?post=4504"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.hongtengdaparts.com\/tr\/wp-json\/wp\/v2\/product_cat?post=4504"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.hongtengdaparts.com\/tr\/wp-json\/wp\/v2\/product_tag?post=4504"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}