Project 635 - 300HP RWD 620

[DADZSUN]

Fritz, thanks for posting specifically to my request - much appreciated.
I’m trying to get properly oriented in the photos - it was tough at first to even get there. Still the securing of the diff to the block below the skirt is eluding me.
...
Byron

Hi Byron,

Here's a couple more pics with the AC compressor and alternator out of the way.

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The differential appears to be between #1 and #2 cylinders. I've since removed the F160 (see next posting for more details) and the VQ35DE AWD block has a hollow upper oil pan that allows the driver side axle 'stub' to feed right to a carrier bearing on the first pic.

FrontAxle2.jpg (154.05 KiB) Viewed 2111 times

[DADZSUN]

Enough good things have happened that it's time for an update!

I've been plugging away on this steady, mostly focusing on front suspension placement & reinforcement. I managed to get the front shock towers identical to G35 stock 13 degree castor. The control arm (ie: TC bushing placement) is also near to stock. This took quite a bit of time to locate and fab.

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CA_Spindle_New.jpg (375.98 KiB) Viewed 2110 times

The VQ35de was cleaned up and some new bits added, including an alternator, starter, and lightened pulley. I have a plenum spacer that I'll wait until after start-up to install. I plan to get an UpRev tune to hit 300hp and more responsive driveability.

VQ_Pulley.jpg (156.4 KiB) Viewed 2110 times

I managed to grab the VQ/Auto tranny and diff/transfer case weight (709lbs).

AWDWeight.jpg (164.57 KiB) Viewed 2110 times

... and did a quick early test fit. The rear frame bracing obviously had to still be cut at that point but it gave us an idea on engine placement for axle operation and firewall location.

TestFitmentAuto.jpg (172.49 KiB) Viewed 2110 times

It became clear that although the VQ could fit in the 620 engine bay, either:

• The engine would have to be placed far enough back to allow for proper front axle alignment and thus the firewall would need a large portion removed to recess the block, or

• Ditch the AWD plan, move the block forward and save the firewall

In the interest of getting this done quick (driving by fall?) and simplify the install, I called and audible and decided on option #2.

TestFitment.jpg (475.21 KiB) Viewed 2110 times

It just so happened that I have a CD009 in the garage originally allocated for the 280z build that I 'borrowed' for 635. RWD will save approx 200lbs, not require any kind of auto shifter mounting and control module for operation, and permit obnoxious burnouts. I will be retaining the G35 wheelspeed sensor feeds and traction control to keep some civility when driving.

The beefy CD009 did require from relief around the tunnel, I plan to use the G35 donor car tunnel to fill this in.

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End result, we've got a fit! Firewall stays intact, there's still a clear path to the steering rack, and room to run the exhaust. Honestly, this is about as good as it can get for a swap this ambitous.

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The hood even closes with a couple of inches to spare - that's with the entire VQ block above the sway bar and cross member, no recessing.

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Next up, I'll be working on the cab. Replace the two rocker arms, and source the G35 tunnel and floor pan to graft into the cab. My son will be pulling the G35's rear subframe and gas tank in anticipation for June work.

Even though I'll loose AWD and winter driving (not really, I plan to drive when there's no snow and rely on TC), I'm really stoked about RWD fun. The truck will still be able to haul stuff and a rack/roof top tent is still feasible.

[DADZSUN]

I've been hammering hard on this truck, the goal is to start it up this September.

Since the last update I've replaced both rocker panels and inner skin. A ton of other little pieces were also replaced. In the pic below I had to rebuild the front arch rib and lower A pillar. There's still a missing tunnel and driver floor pan but I want to wait until the cab is back down on the frame to push that footwell as deep as possible for more leg room. Passenger-side floor pan is done and cab mounting points have been reinforced on all 3 completed corners.

Rocker.jpg (93.52 KiB) Viewed 1998 times

I seem to be exceptionally talented at finding the hard way to do a swap. It started with a KAe Truck block with S13 intake and transmission. With my decision to go from AWD to RWD on this project there were a 'few' changes required.

AWDOilPan.jpg (170.79 KiB) Viewed 1998 times

The big difference was the upper oil pan. Using a RWD pan would 1) allow the starter to properly clear the CD009 6 speed, 2) align the oil filter to the side, 3) create more room in the middle of the pan to sink the block further down.

Yep, after chatting with Andrew I decided to move the engine back 5" and down 4". The firewall will now definitely has to be cut (approx 5" recess) but the improved handling should be worth it.

Here's how it sits now.

EnginePlacement.jpg (163.29 KiB) Viewed 1998 times

EnginePlacement2.jpg (138.25 KiB) Viewed 1998 times

Swapping to RWD mounts further allows the block to be lowered.

Mounts2.jpg (65.21 KiB) Viewed 1998 times

Swapping upper pan was a PITA but fairly straightforward. The windage tray on the AWD was part of the pan and not on the block's craddle per the RWD setup. Thankfully there were holes to simply migrate it over.

OilPans.jpg (137.91 KiB) Viewed 1998 times

Ever wonder how much oil is max? Right at the windage tray it seems.

DipStick.jpg (83.38 KiB) Viewed 1998 times

Why not use the spare RWD block I had on hand? Because my suspicions during the $300 purchased were confirmed, LOTS of shavings in the oil pan. No biggie, I really only planned to use it as a jig and scavenging the parts has already saved me the purchase price. I do plan to dive a bit deeper into the block and see if it's just a quick bearing replacement to fix up.

VQ_Weight.jpg (152.57 KiB) Viewed 1998 times

I'm starting to get a more accurate idea of the VQ/CD combined weight, approx 525lbs w/o oil. I will weigh the stock L20 soon to get an idea on the weight change.

This weekend I hope to complete the engine and tranny mounts and start on the exhaust. Afterwards I'll pull the engine and finish up the engine bay with more reinforcements/seam seal/paint. Next, the firewall will get notched and the cab will get patched up for good.

Lots of work, but also LOTS of fun!

[Byron510]

I was about to ask - if the motor went backwards, why not retain the AWD...
But then I realized that you were likely able to drop the motor down and backwards because the diff and oil pan were changed.

Great progress.

Since you have both the AWD system and the CD09 trans on hand, does it look like the AWD transfer case would mount to the CD09? You know where I’m going with this, but I’m curious if the rear housing on the both box’s might look interchangeable.

Anyways, great to see an ambitious project like this. Please do keep us posted.

Byron

[DADZSUN]

... does it look like the AWD transfer case would mount to the CD09?

Hi Byron, unfortunately the G35 transfer case is integrated into the rear of the automatic transmission.

Even if an external, 'separate', unit was sourced, using the AWD upper oil pan to allow room for the driver-side front axle to clear the block will not mount up to the CD009 manual transmission. For some reason Nissan chose to use a different bellhousing pattern between the manual and auto transmissions.

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In hindsight the AWD engine/tranny/transfer case combo would 'fit' (relative term here) into my 620 but I'm still happy with the idea of -300lbs off the front and a rowdy Nissan version of an El Camino.

300hp in a 2700-2800lbs pickup will be a challenge but I plan to develop my own traction control system using the g35's wheelspeed sensors, install 245/45R17 tires on 17x8 Subaru STI wheelset, and Wavetrac Torsen-based differential to put effective use to all that power.

[DADZSUN]

Project 635 is still plugging along nicely. It's a crap-load of work, but it's fun work.

The front two engine mounts are complete as is the transmission mount.

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I completed the exhaust routing from the stock manifolds to under the cab (to ensure floor pan clearance). I'm using 2" exhaust per bank, each has a high flow cat complete with Vband mounts. The two banks will likely join soon after the tranny mount using the improved G35 'highflow' Y pipe, and continuing with 2.5" to the tailpipe. The exhaust had to be carefully constructed off the manifold to ensure it came down hard enough to clear the deeper footwell I engineered into the frame and cab.

ExhaustManifold.jpg (162.74 KiB) Viewed 1812 times

The front of the frame is now pretty much structurally complete. Once the rear is done I'll remove the body and powertrain and set the frame on its side to close holes, weld, seam seal, then paint.

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Once the frame was complete I cut the cab's firewall to clear the recessed VQ. It fits pretty good all things considered, the intake plenum's elbow is just below the upper cowl. It should be reasonably easy to close in, I'm not yet sure what the impact is yet to the heater box...

VQ35deNotchedFirewall.jpg (152.58 KiB) Viewed 1812 times

With the cab in place I began to work on driver-side control fitment. I've got a set of nice '99 Miata seats to use, they're light, comfy, and minimal size - especially in the backrest.

SeatFitment.jpg (143.24 KiB) Viewed 1812 times

For steering I managed to source an electric steering column that works with the stock G35 steering shaft and UJoint, BONUS! Steering is now done and the assist helps a ton! Steering wheel is a little closer to dash than stock to have a more comfortable reach.

ElectricSteering.jpg (138.34 KiB) Viewed 1812 times

I installed the driver floor pan and will complete the firewall once the pedal box assembly (likely Tilton) is installed. With the deeper firewall and lowered floor pan I managed to gain 3" of much needed leg room.

While I wait for the pedal box, today I started on the rear. Once again my rusty G35x fought me, and one of the main mounting bolts snapped. I'm not sure where I can source another, it's got a taper up top to help centre the rear subframe.

MountingBolt.jpg (132.4 KiB) Viewed 1812 times

Rear subframe is 286lb if anyone is curious. The mounting point measurement appear that they will play nicely with the 620 rear frame rails. I should have a much better idea on my next update.

RearSubframe.jpg (126.62 KiB) Viewed 1812 times

Going forward, I'll remove the stock G35 fuel tank along with the EVAP and returnless fuel system. I'll remove the 620 bed and start the alignment/fitment with the G35 rear subframe.

I'm still confident that I'll be able to at least fire up the truck by mid-Sep.

[greenthumb]

Love the updates! So much ingenuity going on here. The shifter for that CD009 is set pretty far back. With the engine being recessed into the firewall, where does your shifter location end up relative to your seating position?

[DADZSUN]

The shifter for that CD009 is set pretty far back. With the engine being recessed into the firewall, where does your shifter location end up relative to your seating position?

I'm considering two options.

Serial Nine has a sweet solution and is Canadian as well. They appear to also have the shortest traditional rear-mount setup.

SerialNine.jpg (72.42 KiB) Viewed 1783 times

Even shorter, and frankly a bit better placement with my existing setup,is the Autosport Engineering setup. This is a LOT more involved setup requiring permanent changes.

AutosportEngineering.jpg (5.48 KiB) Viewed 1783 times

I'll likely go with Serial Nine and engineer a custom higher (forward) offset shifter if required. I do plan on implementing a few more tricks to get that driver's seat further back which would bring the Serial Nine placement back into play.

Fritz

[DADZSUN]

I made some substantial progress on 635 so I figured I'd post an update before forgetting some of the details.

Front.jpg (84.02 KiB) Viewed 1726 times

The G35 is finally gone giving me more room to reorganize the build. I've got a 20'x40' garage but with 3 Datsuns, 2 of which are in project phase, and a 3rd (510) trying it's hardest to remain an on-going project, room is lacking - and the missus' is keen to get her winter parking spot back!

The bed and rear axle/brake/suspension came off 620 fairly easily.

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Weights were surprisingly similar with only +30lbs added to 635 with the G35 equivalent bits.

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The G35 rear slid under the 620 frame easily enough. Once I get new frame mounting bolts machined I'll be able to fairly easily complete the installation. This is looking to be a very viable swap option for 620 owners looking for an affordable IRS or LSD or disc or 5x114.3 swap.

G35Rear_2.jpg (79.67 KiB) Viewed 1726 times

I'm looking to mount a simple coilover off the spring perch location, or fab up a new mount to replace it (maybe with some adjustability). The top of the damper is only a couple of inches above the frame rail, and since it's now located in the stock wheel arch location (5-6" of headroom), the bed will not have to be modified to house the coilover.

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A cheap eBay strut tower bar arrived today. It's got to be a good sign when it bolts right up and fitment is exactly within the middle of available adjustment. There's 2" of clearance confirming the engine is in fact a bit lower than stock setup.

StrutTower.jpg (150.55 KiB) Viewed 1726 times

... and that's about as far as I can go without more parts arriving. The G35 fuel tank doesn't have a chance of fitting so I'll need a new universal fuel tank (or Pathfinder unit to play nicely with the VQ returnless system). I can't fasten the rear subframe until the mounting studs are machined. I can't dive into rear suspension until the rear is fastened and available clearance is 100% confirmed. I can't complete the firewall until the Tilton pedal box assembly arrives, ditto with the shifter and the tunnel and seat placement.

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It's the first time in months (a year?) that I don't have large outstanding tasks to complete. So I'm looking at smaller cosmetic changes that I know will chew some time. Likely first up is the dash, I've begun filling its cracks with epoxy. I'm going to move to flexible body putty for the final finish but first I think I'm going to first take 1.5" out of the depth (right across) to effectively lengthen the steering's reach. A pretty radical modification for a small change but worth it at this stage IMO. Also, I do plan to remove ~10" out of the rear of the bed to give a more symmetrical look to the cab while retaining the long wheel base.

[Edm620]

"The G35 rear slid under the 620 frame easily enough. Once I get new frame mounting bolts machined I'll be able to fairly easily complete the installation. This is looking to be a very viable swap option for 620 owners looking for an affordable IRS or LSD or disc or 5x114.3 swap."

I like how clean the G35 rear fits under the frame, I've had thoughts about IRS...

[DADZSUN]

...I like how clean the G35 rear fits under the frame, I've had thoughts about IRS...

Nice segue for a quick update. My newly machined 4140 M14 Nissan-spec'd frame studs arrived today.

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I only need 4, and 12 were made so I have two extra 'sets' of mounting studs for anyone who's interested.

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[DADZSUN]

Another update. Seems like the tedious stuff is almost behind and progess appears quicker, at least more tangible improvements.

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I managed to get initial supports welded onto the G35x rear subframe. Decided to roll it out into daylight for the first time in nearly a year to see how she sits. The rear will get a more bracing and cleaned up this week.

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Pinion angle is looking good. The transmission is angled 1 degree down from horizontal (and adjustable via the mount design), and the diff is 2 degrees up from horizontal. Driveshaft will be ordered this week and once installed, the exhaust can be complete.

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The G35 rear subframe sits beautifully in the 620 frame rails. Front mounts are dead centre under the rails and the rear mounts are about 1.5" inboard. There lots of room for suspension articulation. There's even enough room behind the subframe and in between the 620 crossbeams to house a couple Tesla S 5.3 KWH batteries...

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ZFever hacked OEM VQ35DE ECU, and modified harness is done and being shipped back up north. I've got to get the fuel tank sorted out to fire up the VQ hopefully in the next few weeks. Suspension will also be ordered soon.

[Byron510]

The project is really great to follow, thanks for keeping us up to date with all the details - great stuff.

Regarding the subframe studs, will you also threat the other end and bolt to the (modified or fabricated) frame of the truck as per OEM?

Love the progress, looking forward to following further.

Byron

[DADZSUN]

The project is really great to follow, thanks for keeping us up to date with all the details - great stuff.

Regarding the subframe studs, will you also threat the other end and bolt to the (modified or fabricated) frame of the truck as per OEM?

Love the progress, looking forward to following further.

Byron

Thanks Byron.

Yes, I'm trying to duplicate OEM engineering as much as possible. I treated the rear studs similar to the front compression stud, having it penetrate the 2x3 .120 tube, weld both ends.

CA_Spindle_New.jpg (375.98 KiB) Viewed 1161 times

In the case for the rear I actually added another .120 plate within the tube for the frame stud to pierce 3 plates and have 4 welds total. I didn't picture it because it looked ugly (not a lot of room to clean) and I didn't care because it was going to be hidden under multiple gussets anyways.

[DADZSUN]

Interesting progress since the last update, it was one of those 2 steps backwards to go 3 steps forward. Normally I'd be pissed having to redo work, but in this case my patience (age) is keeping perspective of the long-term objectives.

After getting the rear subframe on and temporarily mounting the bed and cab, I realised that the rear frame stud brackets (to fasten the rear subframe) were way too high. The truck looked like a jacked up 4wd machine. Rather than resort to lowered suspension to eat up the gap, I knew that with a bit of effort I could have proper suspension geometry AND lower setup. So I cut the rear mounts almost 3" shorter and now the rear of the truck sits much better.

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While I was at it, I reinforced the rear frame rails to handle the increased torque from the VQ35DE. This will also provide mounting points for additional gussets off the frame bolt/studs, and for the new fuel tank.

X_brace.jpg (96.19 KiB) Viewed 1158 times

Unfortunately, the front needed to now loose 1-2". The problem is that I couldn't lower the frame further down around the engine cross member because that would also lower the cab. The cab couldn't be lowered because the VQ intake manifold was at the top of the notched firewall and I didn't want to cut higher into upper cowl (wiper motor location).

That all changed one night when surfing YouTube and I noticed an interesting feature on a VQ35de swapped Toyota Corolla:

YouTube.jpg (87.98 KiB) Viewed 1158 times

Somehow these guys managed to reverse the upper intake manifold. I have previously tried on my backup block but it turns out I didn't dive deep enough. The trick is to reverse the lower manifold (only), the two upper manifolds bolt the same only now facing backwards. There were some sacrifices, the rigid fuel line between the banks no longer fit, and some accessory bosses required cutting on the upper manifold. Plumbing will also have to be reworked. Regardless, I made the changes, including the decision to run a return fuel system (with flexible lines to suit my clearance requirements) instead of OEM returnless hardlines.

ReverseManifold.jpg (93.24 KiB) Viewed 1158 times

This change not only gave me the 1.5" of height clearance to drop the frame further down around the engine, but it pulled the intake manifold right out of the cab! The limiter was no longer the firewall cowl but the hood.

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I can now close up much more of the firewall with a straight sheet of metal which *should* allow the OEM heater box to remain. I will still need a mild ~2" recess/hatch in the lower firewall to clear hard coolant lines and driver's valve cover, and to provide access for any troubleshooting.

ReverseManifoldClearance.jpg (114.8 KiB) Viewed 1158 times

With the reverse intake manifold a feasible solution, I've since cut the frame's front subframe mounting bosses 1.5" (to allow it to sink further down around the engine). While the G35x front subframe was removed I decided to disassemble it and send it off for sandblasting to remove the copious amounts of rust. Once back, it will be permanently fastened, rather than the previously hoped bolt-in setup (I chickened out due to scope-creep and strength considerations).

Besides that, I've finally received all the proper bolts to install the clutch/tranny so it's now a single unit. Before closing things up I was sure to replace bushings & bearings, and the shifter fork pivot ball with a stronger aftermarket unit since the OEM ones have been known to self-decapitate.

ShifterForkBall.jpg (73.74 KiB) Viewed 1158 times

Up next I should soon be receiving a brand new 720 19 gallon fuel tank. It will be in the same location as OEM, just in front of the rear axle and under the bed. It's a tight squeeze but I think I can make it work and the 50% extra capacity over the OEM 12 gallon tank will be nice. With that, the truck should be ready for a quick fire-up by mid-September. Better to test it now while the cab and bed are out of the way.