Tired 915 - Rebuild or Rebuilt

[gregwils]

92k on the odometer and the ole' 915 seems a little tired, even cranky at times. First gear is a no-go above .00025 mph, second is a little unpredictable from kinda smooth to really notchy regardless of whose gear oil - kendall or swepco. And of course, it likes to sing a little bit on the highway when under light throttle.

My preference would be to rebuild it myself because I am thinking there are a few different things that need addressed in there and I would like to know exactly what was done to it. However, when I add up the potential parts - 1,2,3 ring and dog teeth, a few different bearings, gaskets and seals - it will probably be $1,200 - $1,500 if there are no major surprises.

I have done my motor, so am pretty comfortable tearing it apart on my own with one exception, the R&P. I know there are special tools required and experience that I don't possess to fix if that's a problem, and those could add up to a lot more money. Is it possible to open the side case and examine the R&P to determine if the R&P or bearings are healthy?

The easy way out is to buy a rebuilt unit from a source that advertises rebuilt 915's for $1,800 in Excellence. The amount is fixed, it would have a warranty, I just don't like that I don't know about the overall condition of it. Plus, the price seems a little light for them to make money on the labor and replace a lot of parts. Has anyone bought a rebuilt box from a company that advertises in Excellence for under $1,800? ;- ) Actually, since Wayne doesn't offer the same, I don't see this particular item as competing with him.

[Matt Monson]

You can pull the sidecover and inspect the ring and pinion pretty easily.

Whether you do the labor or someone else does it, rebuild on your own core. We're not very long from a time when having an '86 Carrera still be numbers matching will become relevant to value. Unless there's something wrong with your case that makes it unusable, I wouldn't do the gearbox on a core exchange basis like they do in the ads...

From Pittsburgh, Mike at Body Motion in NJ isn't too far. He can do a great job on a 915 rebuild for you if you are looking for a shop. You'll get a total and complete build sheet with details of what is replaced. But it's not going to be anywhere near $1800...

[db_cooper]

"Has anyone bought a rebuilt box from a company that advertises in Excellence for under $1,800?"

Is the ad near a MM ad? My point is Excellence will take an ad from anybody with a phone number and credit card...

Just rebuild yours..DIY or find a good local shop with references here on the forum.

Throw the Excellence away if you plan to do any purchases out of it.

[Peter Zimmermann]

Greg, from my experience, if your car/915 truly has only covered about 92K miles, then you're probably going to get a nice surprise. The '86 car has the strongest 915, and your chances of not needing a pinion bearing/diff housing repair are very good. I concur with Matt, do not do a "rebuilt" exchange, your chances of getting something inferior to what you have are just too good. My last four or five 915 rebuilds flirted with $4,000 each, so I'm naturally skeptical about $1800 "rebuilds."

That said, temptation suggests that you leave the differential alone, unless the car has done numerous DEs. It is also tempting to not replace any bearings, 92K street miles is not heavy use. My only concern is that you mentioned that the trans will "sing" under light throttle on the highway. This is very unusual, could you please elaborate and post which gear that you're in, and how many rpms that you're running when the noise is loudest, etc.

If you remove the diff side cover you cannot tell if the carrier bearings are good or bad, but you can get a great look at the wear on the pinion head by lifting the diff out of the housing. Bearing replacement is usually done at 150K+ miles, on a properly driven street use car they can last easily into the 200K mile range.

If I was to take your trans in for repair I would anticipate replacing the 1/2 dog teeth, 1/2 synchro rings, and 1/2 slider, and hold my breath while cleaning/inspecting 5th gear. This, of course, can change if you tell me that you don't like your second to third shift sometimes, or how you answer the above question regarding "singing."

[cudabnu]

I took mine apart to inspect everything myself, look good to me, but had 1 bearing sleeve loose in the case. I sent it all out in several boxes (I did NOT take any of the gears off the shafts except for 5th and reverse to get the center case apart) Once it was inspected by the pros at CMS it was another $1200 worth of parts that I needed! Since it is going behind a 3.6 I figuered I'd cry once and have it done right the first time, so it's also getting a new sideplate and 930 bearing, 1 piece bearing retainer, and a TBD.

[gregwils]

Ok. I am a lot of things, but Goober is not one of them. I appreciate the comments and agree with the numbers matching note. Pete - I have your 915 rebuild links saved, so will yank the R&P this winter to take a look.