GMC Syclone/Typhoon Propshaft Replacement
Editor’s Note - I wrote this in response to the many requests for information about the repair and replacement of the front propshaft on Syclones and Typhoons that were coming up on the SyTy mailing list. I was sending this e-mail to the list about once every three weeks as new people came on and asked about broken propshafts. Rather than continue to post it every time, I decided to put it on my website and simply send the link instead. Here’s the Unofficial Guide to Propshaft Repair, which I use to burn excess bandwith which would otherwise be used for pyramid schemes and the theft of copyrighted music. Please hold your applause until the end. After having the friendly local GMC dealer tell me that they wanted $1,500 to replace my Syclone’s worn-out propshaft, I turned to the list and was rewarded by its many helpful denizens with the web address for the company that originally made the propshafts and can rebuild/replace them. They can be reached at http://www.dynotechengineering.com. Mine only needed the front constant-velocity joint (the less-expensive one) rebuilt, so it cost me US$180 + shipping to have it rebuilt. If you broke the more expensive Cardan joint, you may end up having to get a new shaft (less expensive than rebuilding the joint) at around $475, if I remember correctly. Prices can and do change, so don’t quote me on them - I’ve just included them here for the sake of comparison. Also worth noting is the existence of alternatives to the stock shaft, like replacing it with the larger-diameter unit from a Bravada, or upgrading to an ATR shaft. Additionally, any decent shop that does custom driveshafts for 4x4’s should be able to build one for you from scratch, using the flanges from your stock shaft. I mention these options only in passing, because I don’t have personal experience with any of them. I do know, however, that the Bravada swap involves monkeying around with the transmission shift and/or TV cables for clearance. You can run safely without the front propshaft for extended periods, or so I’m told. This is an issue of some contention within ISTA, but the general consensus is that your transfer case can stand to run for a while without anything attached to the front output. I went without mine for three weeks, and the only problem I had was rear tire vaporization any time I applied more than 1/4 throttle. Removing and replacing the propshaft is a pretty simple job too, but you’ll need "torx" sockets in E12 (front) and E14 (rear) sizes. If you dork the bolt heads taking them off, they can be replaced with capscrews of the appropriate size and grade, or you can get new ones for about $1.50 each from GM. The part numbers are 1565-2529 and 1565-2530. Here’s the process I recommend:
Front end of the propshaft, showing the CV joint
The front end "wedged" above the differential flange
Back end of the propshaft, with double-cardan joint. Note the limited clearance for tools.
Jack up the driver’s side of the truck, and put it on jackstands so both the front and rear driver’s side wheels are free to rotate. Make sure you block both right side wheels, since you’ll need to release the parking brake and put the transmission in neutral at certain times. Undo the front bolts first, leaving the transmission in "park" so the shaft doesn’t spin, then take the transmission out of park and turn the front wheel until you can get to the bolts that were hidden before. Repeat the process on the back bolts - if your experience is like mine, you’ll find it’s a tight fit for the socket, and even with a long extension you’ll probably have to lift the front end of the shaft up past its mounting on the differential and ‘wedge’ it up there to get enough clearance to pull the bolts on the back. Be careful - the shaft is ridiculously heavy (20lbs?) and hurts when it hits you in the head. Also, the bolts were installed at the factory by adult male gorillas armed with air wrenches and locktite, so be prepared for some serious grunting to get them loose. Reassembly is the the same thing in reverse. Both front and rear bolts should be torqued to 70 Nm or 52 foot-pounds, and threadlocker (not "permanent"! Remember how hard it was to get ‘em loose?) would probably be good for your peace-of-mind.Let me know how it turns out!
Here ends the epistle.
