New year, new to do list..

[sellersrodshop]

First, happy new yr to everyone! With the new year, focus is on finally getting a few nagging issues resolved with the old truck. I put this thing together 25+ yrs ago before I had a computer, when everything was done via magazine articles, parts catalogs or figure it out and fab it up on your own. Truck was put together to use, as I had another step side that was for show. It’s held together pretty well for being used as a truck and sitting out in the weather all that time, but needs some attention. When I put it together, I used a long tail TH350, with the intention of swapping it later for a 700r4. 20 yrs ago, I started that process which has turned into a complete nightmare, due to transmission builders and shops lying about the product, “losing” my 700r4 and so on (long story). I have a solid guy now who I will take the trans to and find out if I have been duped again and make a decision on whether to continue on with the 709r or just buy a new 4l60e and stand alone controller. The current TH350 leaks fluid out every place possible (has since day one, another long story). The truck was put together with parts from 3 different vehicles, a base Chevy short bed frame with all suspension, steering etc being swapped from a loaded 71 GMC. The rear axle is a 3.08 with brackets changed from leaf spring to trailing arm.

Second major issue to sort out is driveline angles and associated vibrations. When originally built 25 yrs ago, front was lowered approx 5.5”, 3” springs and 2.5” spindles (ECE) Rear was lowered 5” with springs only, rest stock configuration and have had a “cyclic” vibration that comes and goes in waves. I did make a set of brackets a few yrs back for the shocks to improve the angle after the original shocks used were blown out.

Now for the questions and advice part of this novel…

#1 To start on the driveline angle issues, would I benefit from starting with one of the trailing arm crossmembers with the adjustable, multi hole mounting brackets? & work from there to the rear? I would still like to drop the rear another inch and have some solid aluminum I could fab a small lowering block from and machine a few degrees of angle into them if needed to get things correct. Any other tips, recommendations etc will be appreciated and considered to get it right.

#2 any real benefit to going to aftermarket tubular trailing arms with the helm joints vs bushings or continue on with the stock arms and maybe poly bushings?

#3 I know the 3.08 isn’t an optimal ratio with a 700r4 or 4l60e. Considering it’s used as a truck with fuel mileage an issue, would a rebuild of the existing rear using a 3.42 work best or find one of the many 3.73 geared rear ends floating around and just swap it in? Truck will never be on a track and fuel mileage is the major concern. Wheels are 20x10 on the rear with 275’s. I will go to 295’s next tire change, but got a great deal on this package so will run these for awhile.

[wsurf4me]

I did poly bushings with my stock trailing arms and have no issues.

Also have 350 sbc with 700R4, 3.73 rear gear and 29" tall tires. At 80 mph I'm at 2500 rpm with the lockup. I do a mix of city and highway driving, on a good day I average about 12 mpg.

[sellersrodshop]

Originally Posted by wsurf4me

I did poly bushings with my stock trailing arms and have no issues.

Also have 350 sbc with 700R4, 3.73 rear gear and 29" tall tires. At 80 mph I'm at 2500 rpm with the lockup. I do a mix of city and highway driving, on a good day I average about 12 mpg.

I know the biggest mileage factor is aerodynamics. These old things are are pretty much like pushing a brick wall through the air! Figured that out years ago right after I finished this one. Had a 40 Ford couple with the same crate motor, trans, rear gear etc and the coupe got almost twice the mpg as the truck did.

[sellersrodshop]

Pulled it in and did some quick measuring with an angle finder. It’s like the pic below with motor/trans sitting at a downward angle around 4.5 degrees, driveshaft at dead zero and the pinion is down in front at 4.5 degrees. Thinking if I can make a shim to lift the transmission tail up a little to the 2.5-3 degree range in front, I can use one of the trailing arm crossmembers pictured in the first post to get the pinion back around zero and can shim the other couple of degrees to get it where it needs to be. No wonder it beats you to death at 55-70 mph…

[PbFut]

Pinion angle was always a chase in my little track car. The car had a LS2 in a BMW Z3 coupe. Kind of a Carol Shelby sort of monster. Big motor, little car. If the driveshaft angles were not close to perfect, I'd get a pretty sizable overall vibration increasing with speed. I readily saw 160 MPH. So yes for sure get your angles in order. Driveline shops can help. If there is one close by, may be worth having a pro set it up. Poly bushing probably worthless unless you autocross, or more, your truck. Solid bushings and heim joints on the street is flat nuts. My track car uses solid aluminum subframe bushings and heim joints on every suspension pivot point. Rock solid at the track, but it would kill the car within 500 miles on the street. Don't do it.

[sellersrodshop]

Originally Posted by PbFut

Pinion angle was always a chase in my little track car. The car had a LS2 in a BMW Z3 coupe. Kind of a Carol Shelby sort of monster. Big motor, little car. If the driveshaft angles were not close to perfect, I'd get a pretty sizable overall vibration increasing with speed. I readily saw 160 MPH. So yes for sure get your angles in order. Driveline shops can help. If there is one close by, may be worth having a pro set it up. Poly bushing probably worthless unless you autocross, or more, your truck. Solid bushings and heim joints on the street is flat nuts. My track car uses solid aluminum subframe bushings and heim joints on every suspension pivot point. Rock solid at the track, but it would kill the car within 500 miles on the street. Don't do it.

That BMW sounds like fun! I was in the process of gathering things to do a 5.0 swap in a 66 TR-4A when we moved and I sold off a bunch of projects. Kept the running drivers, truck and 69 mustang and have since drug home a 65 fastback mustang that I just couldn’t pass up for the price.