dwragon
OBS Enthusiast
Hello everyone, I read a few snipits of a GMT 400 hydraulic to mechanical clutch conversion, but never found any posts about it. I have a 1994 economized quadrajet GMC 454 one ton dually 4X4 that I bought and made one 600 mile trip between the time the Throw out bearing went from silent to exploded, driving the last 200 miles without any clutch. I am going to try doing this conversion on this truck because I hate the hydraulic setups. This is not my first truck with the hydraulic setup, and none of them have been worth a crap, and I can validly say this as a former GM service technician who cut his teeth on these trucks.
The hydraulic setups were tried by GM in the early 60's and abandoned then because they could not get them out of warranty. GM went back to them later simply for assembly line ease of installation, not because they were the best setup. The aftermarket parts leave alot to be desired, and I have had horrible experiences with them, having had to replace throwout bearings at an average of every 9 months in many other trucks. I believe this is caused by a flat bearing riding on a coned pressure plate surface, with no freeplay due to hydraulic backpressure.
Of course to replace the T/O bearing, you have to pull the transmission, and on a 4X4 thats a royal pain. I searched until found a scattershield with the removable inspection section, which will keep me from having to pull the bellhousing to replace the clutch disk and possibly the pressureplate. That bellhousing off ebay cost me about 375$, and the machine work to make it fit the NV4500 cost another 200$. While in the process of this I discovered that the torsion bars were rust welded into the lower a frames and were impossible to remove. To get the transmission out, I had to cut the bracket into pieces, and by that found out that the bracket was stress fractured anyway, so I will also have to build a custom (read heavier duty) replacement bracket. This will not be a fast task, and time gaps may occur between posting, but I will complete this, so follow it if you are interested.
You must be registered for see images attach
The hydraulic setups were tried by GM in the early 60's and abandoned then because they could not get them out of warranty. GM went back to them later simply for assembly line ease of installation, not because they were the best setup. The aftermarket parts leave alot to be desired, and I have had horrible experiences with them, having had to replace throwout bearings at an average of every 9 months in many other trucks. I believe this is caused by a flat bearing riding on a coned pressure plate surface, with no freeplay due to hydraulic backpressure.
You must be registered for see images attach
Of course to replace the T/O bearing, you have to pull the transmission, and on a 4X4 thats a royal pain. I searched until found a scattershield with the removable inspection section, which will keep me from having to pull the bellhousing to replace the clutch disk and possibly the pressureplate. That bellhousing off ebay cost me about 375$, and the machine work to make it fit the NV4500 cost another 200$. While in the process of this I discovered that the torsion bars were rust welded into the lower a frames and were impossible to remove. To get the transmission out, I had to cut the bracket into pieces, and by that found out that the bracket was stress fractured anyway, so I will also have to build a custom (read heavier duty) replacement bracket. This will not be a fast task, and time gaps may occur between posting, but I will complete this, so follow it if you are interested.