Joe: P.N. 3872476.......

[Joe C.]

is too cheap to be true, on GM Parts Direct, at $156.62. I tried to get a description of the part, but no success. Do you know if this is an inferior, foreign made unit? I want to replace broken spindle with one that has the torsional strength of the original.

Thanks,
Joe

[Joe L.]

Re: Joe: P.N. 3872476.......

Joe-----

The last one of these spindles that I purchased was the same American made unit as always. Don't forget that the price that you mentioned is GM Parts Direct's "base price" (i.e. GM dealer cost). The GM list price for the spindle is about $275. Also, your actual cost from GM Parts Direct will include an additional 15-20% over the base price.

One other thing, though: usually, I always prefer GM parts over just about anything else. However, in the case of the GM #3872476 spindle there is a problem. Very often, if not always, these spindles come out of the box with significant total indicated runout (TIR) on the spindle flange. This produces even more significant TIR on the disc brake rotor when it's installed on these spindles. Readings on rotors installed on one of these spindles of .015" or even greater are common. This is FAR too much and the spindle has to be machined or shimmed to produce acceptable runout of less than .005" on the rotor.

If you use one of the spindles manufactured by International Axle of MN, the runout on the spindle flange is held to less than .0005". This results in a rotor TIR of less than .002" assuming that the rotor, itself, is right.

The one difference is that the International Axle spindle center hub section is smoother finished, "green-anodized" in color and is noticeably different than the stock GM spindle (the hub centers of current SERVICE examples are very similar, but slightly different than the originals). However, the spindle centers cannot be seen with the hub caps installed on the car, so it really doesn't make a lot of difference from a "judging" standpoint. Even if it did, you have to decide which is more important: form or function?

[Joe C.]

Re: Joe: P.N. 3872476.......

Joe:

I did some checking on the spindle. First, a question. Were the spindles that you referred to as having runout problems manufactured by G.M.? I understand that G.M. no longer makes these. They are now made by a few manufacturers, to GM specs. In addition to Int'l Axle, Bairs also reproduces them. Bairs' also look different at the hub because they are machined differently. Dr.Rebuild no longer has any NOS units in stock.

Spoke to Tech at Bairs, and he assured me that the runout is held to .001-.002 max. Your thoughts?

Joe

[Joe L.]

Re: Joe: P.N. 3872476.......

Joe-----

I don't know that GM ever actually manufactured these spindles in-house. If they did, that ended a LONG time ago. However, spindles under this part number have been available in SERVICE from 1965 to the present, unless they have been VERY recently discontinued.

I first purchased a set of these spindles in 1978. Presumably, if GM ever made them in-house they were making them then since they were still used in PRODUCTION at that time. The quality of these units was atrocious. Among other things, the runout on the spindle flange caused the installed rotor runout to be in the range of .015" TIR.

Subsequent to 1978, I purchased several more sets of these at various times and they have been "entered into rest" in my collection. The overall apparent quality improved, but the runout on the spindle flange was excessive in just about every example of the ones I measured. Anything more than .002" TIR on the spindle flange will produce TIR exceeding .005" on the rotor at the measurement point.

I think that what happened on these things is that GM's specs for runout on the spindle flange may not have been too tight. That's because in PRODUCTION, the spindle flange TIR was not too critical. GM riveted the UNFINISHED rotors to the spindles and then machined the ASSEMBLY to a "somewhat exacting" TIR spec on the rotor. So, the actual TIR on the spindle flange was not too critical for PRODUCTION purposes. Unfortunately, the PRODUCTION spindles were NEVER sold by GM in SERVICE as a complete assembly with the rotors. Worse yet, I believe that the spindles, seperately, were supplied in SERVICE with the same manufacturing specs as the PRODUCTION units. This is a case in which the SERVICE spindle, if it was going to be supplied seperately from the rotor, should have been manufactured with different specs. But, I don't think that it was and, I suspect, that's the genesis of the long-standing problem with GM spindles.

The GM spindles are a high nickel alloy forging and are quite strong. However, the TIR problems often render them useless out-of-the-box. Correcting it by machining is a "delicate" operation, expensive unless you have the capability to do it yourself, and, inevitably, weakens the spindle, especially if too much material is removed from the spindle flange face in order to correct the TIR.

I believe that some of the reproduction units on the market may be of "foreign" manufacture. That does not automatically make them bad, though. Just something to consider. I am pretty sure that the International Axle units are of US manufacture. Their guarantee of less than .0005" TIR on the spindle flange makes them VERY attractive, in my opinion. The less TIR, the better. Period.

[Joe C.]

Thanks Joe *NM*

[Craig S.]

Re: Joe: P.N. 3872476.......

Joe - Tom at International Axle has changed his forging dies to produce the two tabs that are present in the original GM spindles. I obtained a set of these out of his first batch last year or so if I recall. He had many made prior to that that did differ in this aspect. However, as you state, his quality and material are superior and the only way to go in my book. He will also special manufacture a set for anyone leaving the green dichromate off, but I think it is a better way to go for protection of corrosion..Craig