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Old 11-28-2011, 01:37 PM   #1
C15_Sierra
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Driveshaft shortening q's

I'm finally getting around to shortening the driveshaft on my C15 LWB...305/TH350 went out, 5.3/4L60E going in. Motor mount adapters position the motor towards the rear 1", plus with the added length of the motor/tranny, I know I need to shorten the stock shaft

When I got the tranny buttoned up, I inserted the yoke about 2/3 of the way in (give myself some error room) and matched up where the carrier bearing holes were on the bracket, since I have a 2-pc driveshaft. Is this the proper way to measure a 2-piece? I figured if I only shortened the shaft in between the tranny and the carrier bearing, I would be good to go the rest of the way (basically mimicking the stock fit). But, since this is my first time, I'm measuring 5 times, asking the forums, and praying that I didn't screw anything up before doing something as irreversible as shortening the d/shaft.

Btw, by that method, I measured 4.5" as the length needed to come off - does that sound plausible to you LS swappers? Not sure which tailshaft size TH350 came out, motor/tranny are long gone (were originally from a '79 Camaro if that helps)

Any other tricks I should know, or just man the **** up and go to town?
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1980 GMC C15 Sierra LWB
Dark Carmine Red/Carmine Int
Was: 250/3spd (1980-88), then a 305/TH350 (1988-2011)
Now: 5.3/4L60E, 2.73 12-bolt open rear
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Old 11-28-2011, 10:34 PM   #2
kwin
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Re: Driveshaft shortening q's

When I had mine shortened in the past I set the slip yoke as deep as possible and let the driveshaft shop make the calculation, It worked for me.

Keith
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Old 11-29-2011, 12:02 AM   #3
yousesteers
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Re: Driveshaft shortening q's

If you are taking the entire driveshaft to the shop just measure from center of u joint to center of u joint and give tehm that measurement they will put the correct slip to it at least that is how i do mine. Do it how ever you want, draw a picture and take it to the shop and explain it to them they will uinder stand and make adjustments as long as they know your measurements and where or how it was measured
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Old 11-29-2011, 12:52 AM   #4
C15_Sierra
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Re: Driveshaft shortening q's

Cool...I'll talk to the shop and see what they say. Thanks guys!
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1980 GMC C15 Sierra LWB
Dark Carmine Red/Carmine Int
Was: 250/3spd (1980-88), then a 305/TH350 (1988-2011)
Now: 5.3/4L60E, 2.73 12-bolt open rear
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Old 11-29-2011, 07:56 PM   #5
76stepsidechevy
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Re: Driveshaft shortening q's

hey what shop are you using ? I never have luck finding anyone local, ive had two made by tom woods and had great luck with them but shipping is still something i'd rather avoid.
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Old 11-30-2011, 12:51 AM   #6
C15_Sierra
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Re: Driveshaft shortening q's

I used Driveshaft Services in East Hartford. I definitely recommend them - read below

I went straight after work on Monday, just dropped off the shaft at closing (they close at 4:30, and I work in Windsor), explained what I wanted done, and by lunch time the next day (today), it was done. For a small operation, I thought it was a quick turnaround, but maybe its customary in this business...

Now, based on what I had read, I was expecting around $100. Chris did it for $170, which was more than I was expecting, but as you're finding, there aren't many other choices. So we talked through what I wanted (just shorten the first half of the shaft by 4.5", as I have a 2pc.) and went through the entire condition of the shaft. Since the truck is old and previous condition of the shaft is unknown, I figured I'd have him replace the u-joints and carrier bearing to be on the safe side. Total cost was $260

Chris' approach was very thorough, as he pointed out some previous work done to the shaft and some potential problem spots (the rear half looked like it was dented very slightly, but balanced out) and told me ahead of time (Monday) that he wasn't going to charge me materials, just labor, to make a whole new rear section if it wouldn't balance out. The truck ran vibration-free before I took the shaft out, so he put it on the balancer after just the cut/weld to see how it was, and it balanced out great. I appreciate that kind of honesty and whether I overpaid or not, I'm satisfied so far.

I found the shop online (one of the only driveline places listed), so it might be worth to take a drive (if you can make it by closing time if you work south of WL) down to East Hartford, or at least give them a call. Chris is the guy I dealt with (its a small shop). Good luck
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-Steve

1980 GMC C15 Sierra LWB
Dark Carmine Red/Carmine Int
Was: 250/3spd (1980-88), then a 305/TH350 (1988-2011)
Now: 5.3/4L60E, 2.73 12-bolt open rear
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Old 11-30-2011, 08:51 AM   #7
rs72z
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Re: Driveshaft shortening q's

Btw, by that method, I measured 4.5" as the length needed to come off - does that sound plausible to you LS swappers? Not sure which tailshaft size TH350 came out, motor/tranny are long gone (were originally from a '79 Camaro if that helps)

That sounds about right after seeing that the prevous th 350 was out of a Camaro.
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Old 11-30-2011, 08:57 AM   #8
C15_Sierra
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Re: Driveshaft shortening q's

Just curious - any idea of what tailshaft size TH350 would have been in a '79 Camaro?

I like playing with numbers
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-Steve

1980 GMC C15 Sierra LWB
Dark Carmine Red/Carmine Int
Was: 250/3spd (1980-88), then a 305/TH350 (1988-2011)
Now: 5.3/4L60E, 2.73 12-bolt open rear
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Old 11-30-2011, 09:11 AM   #9
rs72z
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Re: Driveshaft shortening q's

Quote:
Originally Posted by C15_Sierra View Post
Just curious - any idea of what tailshaft size TH350 would have been in a '79 Camaro?

I like playing with numbers
The Camaro uses the short shaft, which the best i can remember is 6" shorter than the truck long shaft.
I think that is correct, if not i'm sure someone will correct me.
Paul
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Old 11-30-2011, 09:48 AM   #10
yousesteers
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Re: Driveshaft shortening q's

The price does not sound bad to me I think to shorten the rear and lengthen the front in my 4X4 was $430 with all new U joints and rear carrier bearing
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