720 Pickup Suspension Tale

[philip]

This is one for the school books.

When I got this truck, it had the stock steel wheels with LARGE 195/75x14" tires on it. The tires would contact the plastic inner fender when making turns into my driveway. The truck turned with a lot of effort for a little truck even for manual steering.

Upon inspection, I noted the upper control arm bushings were badly worn so I arranged to have them replaced along with the reaction rod bushings and an alignment. The parts got installed but the alignment guy said there was no way he could get the camber OR caster near specs ... implying that the frame was sacked. Something on the order of 2 degrees negative camber and a LOT of positive caster on both sides with no alignment shims present.

So ... I found and installed a set of upper ball joint spacers which pushed the camber out at least 1+ degrees which still left the total setting at about 1/2 degrees negative. No change to caster. That improved tire wear.

I drove around for about 18 months like this and have gotten decent tire wear but ... the steering / turning effort remained on the high side.

IN the past few months, the truck developed a shimmy when the right tire crossed over bumps especially with the tires aired higher than 30 psi. I checked here for Al's earlier experience with idler arms and made a couple of discoveries. Idler Arm models.

This past weekend, while under the truck replacing the idler arm, I studied the suspension ... wondering. I couldn't put my finger on just what looked odd but something just looked "off."

A friend stopped by to supervise. He made an innocent comment about the tire not seeming to be centered in the fender's wheel opening. I got to thinking and then ... it all came together. Too much caster, insufficient camber, high effort steering, lots of tire tilt during sharp turns, and tire scraping the inner fender on turns with a bounce. Hmmm. Time to visit the boneyard to see other 720s. Maybe I'll get an answer.

Here's the truck today. See how the tire is not centered in the wheel opening?


Measurement from the fender to the tread edge.


Visiting nearby mini-truck graveyard (Ferman's Mini-truck, Santa Ana, CA) I took some pictures of a 1983 720's left suspension with my cell phone camera.
Note A-arm is shaped to offset forward the ball joint.


Now look here! This my truck with the LEFT upper A-arm on the RIGHT side!! Furthermore, the frame tower mount does not orient the A-arm perpendicular to the frame. Rather, the tower angles the A-arm toward the rear a few degrees. Notice too the 1" thick ball joint spacer I installed to gain some camber.


Here are a pair of 720 upper A-arms.


How this all got reversed is a guess. My belief is ... Nissan committed this sin while the front end shop reinstalled the A-arms back as they found them.

Who'da Thunk It? (Grrrrr)

I'm going to a different shop later this week to get things fixed. May also get a front sway bar installed.

[kassim503]

ahahaah, that is one for the books

[philip]

Got my truck back today. The mechanic had a few things to say to me about the job. Seems that getting the left upper control arm out was such a bear due to insufficient clearance at the inner fender that he nearly gave up! He had to widen the previous slice and bend one side of the slice about an inch to get the arm out! Stuff happens. I've heard similar tales about the older Toyotas too.

The arms came out, got reversed, ball joint spacers removed, new (used) front sway bar installed (the truck left the factory without one), the ride height dialed back up to stock, and a complete alignment.

WHAT A HUGE DIFFERENCE DRIVING and especially CORNERING!! MUCH less steering effort to make tight turns and no more steering shimmy after sharp bumps. Cornering improvement is almost beyond words.

Note that now the tire is centered in the fender opening.


Reversing the upper control arms moved the tire forward about 3/4". Also reduced positive caster considerably and restored camber adjustability.


Compare the upper ball joint now with the "before" photos post. Notice the ball joint is slightly ahead of the shock absorber instead of behind it. Upper ball joint spacer not reused.


This truck did not get a sway bar from the factory. It has one now and what a difference in cornering it makes!

[philip]

SNIP
How this all got reversed is a guess. My belief is ... Nissan committed this sin while the front end shop reinstalled the A-arms back as they found them.

Who'da Thunk It? (Grrrrr) SNIP

Yesterday, I swapped the Datsun for a friend's '98 Jetta TDI that was having eletronic migrains again (no turbo & several failure codes). This is the same fellow who bought the Datsun brand new in '82.

He drove the truck around quite a bit doing errands. He called me later in the day to tell me the truck NEVER made U-turns with that little effort. "What did you do to the steering?"

Yep... October of '81 must have been rookie line assemblers training month at the Datsun/Nissan truck assembly plant.

[Zoltan]

what does it take to install sway bars? Any drilling ? What year trucks can I get the swaybars from?

[philip]

what does it take to install sway bars? Any drilling ? What year trucks can I get the swaybars from?

The FSM shows all 720 "capable" of having a front sway bar. But like mine, the cheap models didn't get 'em. There was no drilling involved and all frame holes had threaded lugs. Lower control arms had the dished hole for the sway bar link rods. It's a bolt-on. WELL worth it!

[Zoltan]

I think your truck is same as mine, except for the A-arms mix up. Mine has about 156K miles and I am looking to replace the front struts as well. What would you recommend? For the sway bar, can I look for trucks as far as 1986? I assume the sway bar can come from a gas truck as well.

thanks

[philip]

I think your truck is same as mine, except for the A-arms mix up. Mine has about 156K miles and I am looking to replace the front struts as well. What would you recommend? For the sway bar, can I look for trucks as far as 1986? I assume the sway bar can come from a gas truck as well.

thanks

These trucks use "double wishbone" or "A-arm" suspension with shock absorbers. They do not have load bearing "struts" (McPherson suspension, 1947)

For shocks, I've been using Monroes. There ARE better shocks around but Monroes have a Lifetime Warranty through your retailer ... so long as you keep the sales reciept. You will be given a free replacement EVERY TIME the thing starts leaking oil. I've used this warranty twice.

This is important because the "Value Engineers" at "Datsun/Nissan saw fit to remove the travel stops from under the A-arms (they are present in 620 trucks) and instead, use the extension limits of the shock absorber to limit travel when the suspension unloads. I have not investigated using the shock from an early ('81-'82) 4x4 ... thinking being it might have the same compressed length but slightly longer extended length. Look into that!

The sway bar and connecting rods can come from any TWO wheel drive 720.

[Zoltan]

I was looking into Monroe shocks, but I am absolutely unfamiliar with them. Checkers lists a whole bunch, but when I go to Monroe's web site, these products are not listed there any more and I couldn't find any information on these. Perhaps you could help me to chose one:

This is what my local Checker's has:
#20721 Gas-charged, heavy duty ($12)
#59016 Lt truck, gas-matic ($15)
#59316 Lt truck, gas-matic ($22)
#37047 Sensa-track ($33)



Monroe lists these:

for general purpose:
#32206 Monro-matic plus

For towing and hauling:
#58417 Sensa-track (1 pair/pk)
#31162 Monro-matic plus
#MA802 Max-Air


I think a general purpose shock would suffice. I don't carry heavy stuff or haul.

[philip]

I was looking into Monroe shocks, but I am absolutely unfamiliar with them. Checkers lists a whole bunch, but when I go to Monroe's web site, these products are not listed there any more and I couldn't find any information on these. Perhaps you could help me to chose one: SNIP
I think a general purpose shock would suffice. I don't carry heavy stuff or haul.

For shocks, I have been dealing with a local Carquest warehouse. Their house brand shocks are Monroe-matic+.

I have:
Front Monroes: 32206 "Monroe-matic-Plus"
Rear "house branded": 47320 OEM shock (I prefer a ligher dampened shock for the rear)

Both of these are gas charged shocks that come tied down fully compressed.

You would probably be happy with Monroe-matic or SensaTrac for the front and a softer OEM shock for the rear. Remember to file your receipts JUST IN CASE of shock failure.

"No tickie, no washie"

[claybodie]

As usual, thanks for the great information.

I am looking to replace the shocks in both front and back. I'm also looking at carrying some pretty heavy fuel loads from time to time with a spare tank in the back. As it is, my truck sags pretty sadly with a moderate load in the back.
I don't know too much about this, but a few things have been suggested to me:
- have the leaf springs replaced and beefed up to handle better loads.
- replace the shocks with adjustable air shocks.

Any comments on this?

[philip]

As usual, thanks for the great information.

I am looking to replace the shocks in both front and back. I'm also looking at carrying some pretty heavy fuel loads from time to time with a spare tank in the back. As it is, my truck sags pretty sadly with a moderate load in the back.
I don't know too much about this, but a few things have been suggested to me:
- have the leaf springs replaced and beefed up to handle better loads.
- replace the shocks with adjustable air shocks.

Any comments on this?

The most weight I ever had in the poor ol Datsun was this 300 mile trip in 2004 where I ferried two motorcycles from Beatty, NV to Los Angeles. Honda ST1100 (about 760 lbs), Yamaha TW200 dirt bike (about 300 lbs), and we two humans (est 325 lbs). Getting across Death Valley involves two steep, nearly mile high passes. This was overloaded for the ol Datsun's power, marginal front brakes (larger starting in '83), and loaded weight bias. I'd limit payloads to 1000 lbs and NO MORE. The rear end didn't really bottom out nearly as much as the front end topped out over minor bumps. As far as wallowing around turns, THIS would have been the time to have had that front sway bar in place.