What should i do first.

[eighteenninetytwo]

The two big projects i need to get done at some point (no timescale necessarily) are :
1. Unlifting down to stock or 2" max
2. New transmission (plenty o leakage at present - mechanic says it's worn and in last 10% of life and to stop the leak means taking it out so I figure I might aswell get a new one instead)

Question is - which do i do first? Does the lift height affect the alignment of transmission and therefor I should get that done first to avoid having to change the tranny up again when the truck is unlifted. On the other hand, does being lifted make the tranny change easier with additional access etc?
any advice ?

[79 silverado]

With the info you have here it is difficult to answer precisely... but here is what my thoughts on the matter are and you can fill in the blanks.

There are two kinds of lift kits:

1) Suspension lift in which shackles/springs/etc are changed out. This kind of lift also changes the angle which the driveshaft runs at, and may require a lengthened driveshaft to cover the increased distance from the output to the differential. If you are changing out the driveshafts later there is the chance of messing something up ad creating a leak at one of these output shafts in the future if you are not careful.

2) Body lift in which the factory body mount bushings are replaced with spacers/blocks to lift the body higher off the frame, but leave the chassis and running gear unaffected in their stock configurations.

Sometimes someone uses a combination of a couple inches frame, couple inches body.

If your lift is purely a body lift kit, then I would go ahead and change out your transmission first, improve driveability and reliability, and know that the chassis and running gear do not need to be touched when you alter the lift kit height.

If your lift is a combination of body and suspension, and the way you want to change your ride height is to remove only the body lift and keep the suspension lift kit in place, then same answer as above.

If your lift is a suspension lift only and you are going to be removing this suspension lift and changing around the other driveline parts I would probably just do everything at once later.

The other thing I should add is that the crossmember and mounting point of the transmission unit itself remains the same with respect to the frame rails in any scenario unless you are putting in an aftermarket crossmemeber or anything like that.

[eighteenninetytwo]

The kit currently on it is about 4 inches, maybe a little more. In the the rear it's just blocks new shocks and u bolts. At the front it's new leaf springs also. The thought occurs to me having read your answer that it is entirely possible that the previous owner (mexican drug dealer) put the lift on without probably considering the effect it would have on the transmission alignment etc and this is one of the reason for the excessive leakage I'm seeing form the transmission. I'm starting to think that getting both done at the same time is the way forward thought that means paying someone to do it as opposed to doing the suspension myself.

[Ski-me]

Do you have a transfer case drop or is it still up in stock location? If it's still in stock, then there isn't any undue alignment issues (engine/tranny speaking). But, having a 4+" lift tends to have large tires too...and that's what strains the transmission.

I'd probably do the tranny first and then hit the junkyard for new front springs and shocks. If you just have blocks in the back, take those out and install new u-bolts.

Suspension, you can probably do yourself. Tranny, leave to experts. Do some research on local shops doing re-builds. Some do it better than others.....

What about driveline? Does it look stock? If so (and considering the lift), the slip yoke is probably pretty far out.

Any vibration right now in truck?

[swissarmychainsaw]

Can't say much about the lift situation, but:
When you decide to have your tranny done, I can recommend a good builder in the East Bay. Might not be real close to you, but I have endured the pain of bad transmission builds (AAMCO!) and would not wish that on anyone.

Keith's transmission in Hayward. It's worth a trip to talk to the boss, Mike.
http://www.yelp.com/biz/keiths-trans...-castro-valley

I have not had work done by him, but while I was dealing with the AAMCO fiasco I went and talked to Mike and wish I had.

Nick