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Discussion Starter · #1 · (Edited)
Edit: Okay, she's up and running. Here is a list of things I've learned doing this swap - might save some other people some time.

1. Dimensions. Though the 70 and 80 are *similar* in overall dimensions, the 80 is bigger through the center and the rear crossmember mounting point is much further back. Because of that, I seriously doubt your current exhaust will fit - though there might be exceptions.
2. I used a TH400 yolk provided by Hughes and did not have to alter my driveshaft length at all. I tested free-hanging and on the ground and it looks good. If anything, I would LENGTHEN the driveshaft 3/16-1/4" (obviously not going to happen)
3. Be smarter than I was. When you have your flexplate bolted up - if you are using a crankshaft snout extender adapter gizmo, put your converter up against it and make sure the snout bottoms out against the adapter and verify your flexplate spacing. I had concerns with mine - but it ended up being fine. I removed the dust cover and the converter bolts just to triple check after the fact (added an hour+ to my Sunday afternoon)
4. Not just 80 info - but if you are looking for a keyed hot wire at the back of our trucks, the RED wire for the trailer hitch wiring is not connected from the factory. It is hanging down in front of the fuse box in the engine compartment probably hooked into a loomed wire. There is a post (front of fuse box and closest to the engine) next to the jcase fuse #32. It's a 30 amp fuse. All you need to do is connect that red wire to the post and put a nut on it - bam. Keyed power to the back of your truck.

I'll update if I think of anything else -


First I'd like to thank Joe for the crossmember and TCM - he's great to deal with.

Now - on to my story. Broke my 5th 70 in rush hour traffic a few weeks ago. I've yet to break one under WOT - but I certainly have a way of killing them. Couldn't justify putting any more money into that transmission as the last two builds had every wizz-bang high dollar part you could buy in them and it's still a fragile little bitch of a transmission.

The 80 fits in our trucks like it should have been there to start with. For some reason, I didn't have to do anything to my driveshaft except for switch the yolk. Perhaps it's because I'm using a TH400 yolk from Hughes instead of the factory 80 yolk - but the fit was perfect. I did have to trim the "ears" off the 80 to get it to fit around my 1 7/8" primaries, but that was the only real problem.

I wont get a chance to work on it again until Tuesday/Wed - but I'll keep ya'll updated as this progresses.



The 80 isn't physically THAT much bigger than a 70 - I was a little depressed until I looked at the input and output shafts and compared the general beef through the center of it.



Hughes SFI flexplate and crank pilot spacer --



Here is one of the ears I removed --




TH400 yolk - it will slip all the way in. We dropped the truck down off the lift to let the axle come up and push it in - only moves it about 1/4" for future reference.



Laying under the lift for a overall pic ---

 

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WANNABE SS OWNER
Trailblazer SS 2wd
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Looks great Rob! You Have had more trany problems than JJ but that 80 should put a end to them:cheers1:
 

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TrailblazerSS
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What eles did u need wit that TH400 yoke......if possible could u get me a link to where u got the yoke n the other parts needed to connect to drive shaft thanks
 

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Discussion Starter · #5 ·
What eles did u need wit that TH400 yoke......if possible could u get me a link to where u got the yoke n the other parts needed to connect to drive shaft thanks
Pliers to remove the snap rings. A big pair of channel-locks. A socket approximately the size of the joint caps and a big hammer.

1. Pull the snap rings
2. Support the yolk on a piece of wood (I used a 2x4)
3. Put the socket on one of the caps and beat the shit out of it until it pushes out the other side
4. Use the channel-locks to grab the mostly pushed out cap and pull it out.
5. Once one cap is off, you can get the joint out pretty easy
6. Reassembly is the opposite - just make sure to put some new grease in the end-caps to secure the roller bearings - they can be a pain in the ass if they fall out

U-joints are easy - I think a lot of people are intimidated by them, but it's honestly not a complicated process. It's even easier if you have a press on hand.

Edit: As far as sourcing the yolk - It's from Hughes - call and ask for Pete, he's a super good guy.
 

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Discussion Starter · #6 ·
I have a question about the shifter cable bracket. I've read through all the thread here and saw that people are referencing the need for a cargo van bracket - I was wondering if there were any other alternatives (want all my options before I hit the u-pull-it yards) and also if anyone had some pictures of theirs. I'd love to see a good pic of the bracket on a functional 80 swap -

Thanks guys -
 

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Discussion Starter · #9 ·
What's the cost of a 80 vs built 70
A built 80 is certainly more than a built 70. But a built 80 is way cheaper than a handful of built 70's. As crappy as that is - it's the reality we get to deal with. If you are making any sort of power with your TBSS, you are on borrowed time with the trans.
 

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Trailblazer SS
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Long time no see! Good decision on trans! I remember when u were on trans 2 lol
 

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08 Black Granite
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Great pics! Thanks for sharing, man that crossmember sure is sexy!

What size stall are you running?
 

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Discussion Starter · #13 · (Edited)
Great pics! Thanks for sharing, man that crossmember sure is sexy!

What size stall are you running?
Hoping to foot-brake it to the mid 3000's and have it flash close to 4k. I'll just have to wait and see how it works, my last converter from Hughes was way too tight. I was exceptionaly specific when ordering and there was no guessing - I know exactly what my truck weighs on each corner - I know exactly what it makes at the wheels... I really hope they got it right.

Just judging from shear size - I'm optimistic. The 80e converter is way smaller than my old 70...

 

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07 TBSS
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I'm gonna have to this swap next year, can somebody make a sticky on every part we need and wed site we can obtain the parts from!?!? Maybe I'm a idiot but it seems like everybody comes up wit there own ways of doing this swap, besides the 6 different flex plates we can use...

BTW who sells or makes that crossmember ?
 

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Discussion Starter · #15 ·
I'm gonna have to this swap next year, can somebody make a sticky on every part we need and wed site we can obtain the parts from!?!? Maybe I'm a idiot but it seems like everybody comes up wit there own ways of doing this swap, besides the 6 different flex plates we can use...

BTW who sells or makes that crossmember ?
Well - there really is a ton of different ways to do the swap. I chose the route I did for several reasons not the least of which was Joe's swap kit is already in use by several people and I didn't feel like being a beta-test for some of the newer solutions.

Crossmember is from Joe @ Left Coast 32. He's got a few threads in this forum about his swap kit.
 

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TrailblazerSS
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Pliers to remove the snap rings. A big pair of channel-locks. A socket approximately the size of the joint caps and a big hammer.

1. Pull the snap rings
2. Support the yolk on a piece of wood (I used a 2x4)
3. Put the socket on one of the caps and beat the shit out of it until it pushes out the other side
4. Use the channel-locks to grab the mostly pushed out cap and pull it out.
5. Once one cap is off, you can get the joint out pretty easy
6. Reassembly is the opposite - just make sure to put some new grease in the end-caps to secure the roller bearings - they can be a pain in the ass if they fall out

U-joints are easy - I think a lot of people are intimidated by them, but it's honestly not a complicated process. It's even easier if you have a press on hand.

Edit: As far as sourcing the yolk - It's from Hughes - call and ask for Pete, he's a super good guy.
Use the same u joint or new one an snap rings new ones or reuse thanks on help
 

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Discussion Starter · #19 ·
Use the same u joint or new one an snap rings new ones or reuse thanks on help
Same u-joint - same caps - same snap rings. Same everything other than the TH400 yolk. Took me all of about 10 minutes - and thats because I waited for some PB Blaster to soak in before hammering it and because I took the 90-degree die grinder with some buff pads to the caps to gently polish them up for easy reinstall. Could be done quicker. The only tricky part is making sure the roller bearings dont come out of the caps and a dab of grease all but eliminates that possibility.
 
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