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Thread: Differences between a Cat 951 and a Cat 955

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    Differences between a Cat 951 and a Cat 955

    What are the main differences between the 951 and 955 Cats? I have a 955 but know where there is a 951 in a salvage yard that I can get parts off of cheap if anything will interchange. I don't know why it is in the salvage yard, but it is complete except for the final drives. I don't know the year or if it is a C with a 3304 engine or not. My 955 has the 3304 in it. Maybe the cylinders, bucket, rollers, idlers, hood, gauges, seat, radiator, ect are the same.

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    Quote Originally Posted by MikeVincoli View Post
    What are the main differences between the 951 and 955 Cats? I have a 955 but know where there is a 951 in a salvage yard that I can get parts off of cheap if anything will interchange. I don't know why it is in the salvage yard, but it is complete except for the final drives. I don't know the year or if it is a C with a 3304 engine or not. My 955 has the 3304 in it. Maybe the cylinders, bucket, rollers, idlers, hood, gauges, seat, radiator, ect are the same.
    I have a 951B and it has the 3304. I also have a 955K also with 3304. Difference is, the 955k is turbo charged, probably different size valves in head, possible different or at least set up different injection pump. I can tell you that undercarriage parts are same until you get into the later serial numbered 85J's and 13X's. The tracks links on the 951 are 2 links shorter than the 955K, sprockets, rollers idlers all same.
    Nick

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    The hydraulic cylinders are not the same, bucket on 951 smaller, bellcranks different. The hydraulic pump is actually not even connected the same way, 951 is attached to engine, 955 is mounted to the torque converter. Hope this was of some help.
    Nick

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    Thanks for the reply Nick. I am going to look at the tractor tomorrow to see if there are any small parts that look the same. I have a 13X 955L, so like you said, the tracks are probably different. Maybe it will have a light package on it or a set of front sweeps or a air precleaner, we'll see. Thanks again for the reply; I would have thought they were more simular by the way the looked from the outside, now I know.

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    Quote Originally Posted by MikeVincoli View Post
    Thanks for the reply Nick. I am going to look at the tractor tomorrow to see if there are any small parts that look the same. I have a 13X 955L, so like you said, the tracks are probably different. Maybe it will have a light package on it or a set of front sweeps or a air precleaner, we'll see. Thanks again for the reply; I would have thought they were more simular by the way the looked from the outside, now I know.
    Yes, your 13X has an 8" pitch, the 951C has 6 3/4" pitch. They also have different width track pads. Your machine is 15" the 951 is 14". I have used 15" pads on my 951 even though cat they don't fit, they are close but work fine. Feel free to ask anything else that has you scratching your head about the differences.
    Nick

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    Highdrive, the 951B is fitted with the 330C engine (4" 3/4 Bore) using the scroll style injector pump, the track pitch was 6"3/4 from new then converted to 6".91 spec due to product change by CAT, the rims and track groups (Chains+pads) had an even number of teeth and bushings giving a non hunting tooth effect, the 951C is fitted with the 3304 engine again with the 4"3/4 bore, using the sleeve style fuel system and radiator mounted oil cooler, sealed loader frame with a revised return to dig ram mounted valve control, the main loader chassis was plated for extra strenght, twin horns fitted plus a few other small details changed, the track pitch on the 951C was 6.91" with an extra link to reset the hunting tooth effect, the hydraulic cylinder size was 4 1/4" on both B and C models, the track pitch is eay to spot by the pad size front to back of a plate.

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    Quote Originally Posted by tctractors View Post
    Highdrive, the 951B is fitted with the 330C engine (4" 3/4 Bore) using the scroll style injector pump, the track pitch was 6"3/4 from new then converted to 6".91 spec due to product change by CAT, the rims and track groups (Chains+pads) had an even number of teeth and bushings giving a non hunting tooth effect, the 951C is fitted with the 3304 engine again with the 4"3/4 bore, using the sleeve style fuel system and radiator mounted oil cooler, sealed loader frame with a revised return to dig ram mounted valve control, the main loader chassis was plated for extra strenght, twin horns fitted plus a few other small details changed, the track pitch on the 951C was 6.91" with an extra link to reset the hunting tooth effect, the hydraulic cylinder size was 4 1/4" on both B and C models, the track pitch is eay to spot by the pad size front to back of a plate.
    TC, I have my 951 since new and it has the 3304, just rebuilt it so no mistake there. It came with the 6 3/4pitch and I changed the sprocket to use the 6.91 pitch, allowed my to use the track group from my 955K minus 2 links, I also changed the return to dig valve to the 951 C design. The 951C actually had 1 link removed when changed to the 6.91 pitch to allow for the increased pad and bushing size, went from 40 link to 39. The reason I have 2 links removed from my 41 link 6.91 pitch was so I could use that track group for either the 955K or the 951B with C upgrade. I just used 2 master pins when using for the 955K. Anyway that's it! lol
    Nick

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    Highdrive, in your previouse post you quoted 951C pitch as 6" 3/4?? not 6"91, I have never seen a B series loader fitted with the 3304 Ex factory, if this engine is fitted to your loader it must be a U.S.A. thing as the B's all had 330C power units fitted? LOL

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    Quote Originally Posted by tctractors View Post
    Highdrive, in your previouse post you quoted 951C pitch as 6" 3/4?? not 6"91, I have never seen a B series loader fitted with the 3304 Ex factory, if this engine is fitted to your loader it must be a U.S.A. thing as the B's all had 330C power units fitted? LOL
    Your right TC, it seems I did mistakenly say the 951C was 6 3/4. My 951B was an 86J949 made in USA with the 3304. My older 955H had the D330 which was also in the early 955K 61H serial #. Interesting that all the 951's where you are only came with D330. I wonder if it also was in earlier 951B's here too, although mine is a very early one, who knows.
    Nick

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    Highdrive, the engine I expect to see in the 951B series loader is the D330C there is also the D330B and the D330 units, the easy way of spotting a 330C from a 3304 is firstly the water pump location , if its high up on the top of the front gear case and its fitted with the scroll injector pump its a 330C, if the water pump is bolted into the front face of the gear case low down its a 3304, they would both be PC style engines, the basic visual look of the engines are identical, not trying to thrash a dead horse! but my 951B that is up near the end of the B series production Sr No 1662 or something like that is fitted with the D330C Ex Factory but it ain't built in the U.S.

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    Quote Originally Posted by tctractors View Post
    Highdrive, the engine I expect to see in the 951B series loader is the D330C there is also the D330B and the D330 units, the easy way of spotting a 330C from a 3304 is firstly the water pump location , if its high up on the top of the front gear case and its fitted with the scroll injector pump its a 330C, if the water pump is bolted into the front face of the gear case low down its a 3304, they would both be PC style engines, the basic visual look of the engines are identical, not trying to thrash a dead horse! but my 951B that is up near the end of the B series production Sr No 1662 or something like that is fitted with the D330C Ex Factory but it ain't built in the U.S.
    TC, as I remember, the D330 has a spring tension on the fan belt, also the head is very different with all those rubber inserts with the brass centers where the head mates with block. I've had the engine in my 955H with that engine apart a few times.
    Nick

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    Quote Originally Posted by Highdrive View Post
    Your right TC, it seems I did mistakenly say the 951C was 6 3/4. My 951B was an 86J949 made in USA with the 3304. My older 955H had the D330 which was also in the early 955K 61H serial #. Interesting that all the 951's where you are only came with D330. I wonder if it also was in earlier 951B's here too, although mine is a very early one, who knows.
    Nick
    Highdrive, I'm sure you'll find the engine in your 951B is in fact a D330c, it came out in about 1968 and was as you say a very different looking engine to the original D330. The c series engines were around until 1972 when they became the 3304 and 3306 respectively. In the case of the 951 the introduction of the 3304 coincided with it becoming the 951C at serial 86J1992. As tct said the easiest way to tell the c series from the later 33xx series is the water pump and the c series engines were still fitted with canister type oil filters as opposed to the spin on one on the 33xx engines (though the c series introduced the spin on fuel filter...I've often wondered why they didn't do the same for the oil filter??).

    Finally, there's one other surefire way to tell..the D prefix engines shared the same serial number as the machine. When the 3 series came along the engines got individual serial numbers.
    Last edited by Rusted; 05-12-2012 at 08:39 PM.

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    Highdrive, it looks like your motor is fitted with a few less HP than you thought LOL

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    Quote Originally Posted by tctractors View Post
    Highdrive, it looks like your motor is fitted with a few less HP than you thought LOL
    TC & Rusted, after checking the serial number plate on the engine which shares the same # as the machine I guess what I've always thought was a 3304 is in fact the D330C. I have a spin on oil filter that I converted along with the updated lift kickout, I have a fully enclosed rops cab which is rarely seen on a 951 of any vintage. I was comparing it to my D5HLGP engine which does have a 3304 and it sure looks similar. Water pump mounting seems to be different. The 955H I have with the early D330 is very different, with the belt driven water pump with tension spring. Funny, when I ordered the liner kits and sent the head out for rebuild that the subject never came up as to what engine it was. I thought for sure I at least knew what I owned! lol
    Nick

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