Exhaust routing at crossmembers?

Discussion in '1976-1983 Pickup Discussion' started by Perkolator, Oct 19, 2020.

  1. David Woods

    David Woods Newbie

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    Oh BTW Perkolator, if I were in your shoes with the crossmember you have pictured I would be elated. It would solve a ton of problems because of the added clearance from the arched relief of the crossmember. However, I would add a little modification by welding a 6" long steel channel section to the bottom of your crossmember that is deep enough and wide enough to provide rattle clearance but would serve as a skid-plate protection for the pipe.
    Otherwise, it is possible to bend shut or break the pipe as it gets crushed between the crossmember and whatever big rock, root or stump almost cleared it. I know this because my son and I had to drive with our heads out the window because where there is exhaust leak there is toxic CO gas that will seep into the cab. We were way up between Mt Rainier and Mt St Helens on fire-roads when we cracked the exhaust but it was summer so we were like two dogs with heads out the windows until we got back to civilization. Talk about dry eyes and mouth; I don't know how dogs do that and look happy.
    Driving out was really the only option for us. That was a very dangerous thing to do but it was a calculated risk because I had a CO meter/alarm that I would keep from tripping by having the windows fully open. Also, the heater controls must be set to full outside vent-in fresh air and at maximum blower speed to attempt to positively pressurize the cabin.
    Always maintain a CO alarm in the vehicle on any older vehicle be it car, truck plane or boat. I am surprised that onboard CO monitoring is not a required safety feature on current OEM motor vehicles. That should have been mandated long ago as an occupant safety feature, like seatbelts are.
    DAW
     
  2. Perkolator

    Perkolator Toyotaholic

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    Well I know there were many changes for the 75+ trucks, when they did the refresh - so that’s likely why Jetas’ and Pearce’s trucks have different crossmembers than my 75.

    I would also assume that there may be different crossmembers for the different transmissions these trucks were equipped with. Mine is a 5spd/W50 trans truck - is yours the 4spd? If so that may explain the difference
     
  3. David Woods

    David Woods Newbie

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    Mine is a 4sp although I have a W50 to put in this summer. I know that the bolt-up from the mount to the crossmember is a little different because the two trans mounts are different but that mod is easy. The crossmember shape could be different to and I'm going to find out.
    There is a guy down in Aberdeen that has a barn full of early parts: body, suspension, engines, etc. I guess I'll make the trek down there.

    I appreciate the feedback. If I hadn't seen your photo I would not have known there was another design crossmember that will bolt onto my truck other than the straight bottom type on mine.
     
  4. David Woods

    David Woods Newbie

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    A follow up on this discussion: I saw a 2nd generation truck in a parking lot and peeked under it to see the crossmember. It had the type I need with the arch in it rather than straight across the bottom. In fact it had an arch toward both of the ends, not just the drivers side. It looked like a '75-'76 but I couldn't see a VIN. It was lowered so I couldn't get a great look but I think there was a catalytic convertor just behind the crossmember. That wouldn't have worked if the arch wasn't made in that factory crossmember.
    I was set to build an oval SS pipe to be below my crossmember for ground clearance but it would be far easier to find a curved crossmember. Well, not exactly easy since it is getting harder to find an old intact truck but at least I know what I'm looking for.
    Does anyone know of a crossmember like I'm describing up here in Seattle?
    Thanks.
     
  5. David Woods

    David Woods Newbie

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    OK, I am replying to my own posts like a running monologue here....but I want to share what I found as a solution to my exhaust routing impasse.
    I found a '78 SR5 that has the crossmember that has a raised relief/arch on the left side to allow for an exhaust pipe to route under it.
    I have a W50 and a P51 and can bolt either in. The donor truck for the crossmember has a W50 trans that I will probably buy for a spare.
    I have heard alternative facts regarding the ratios of truck W50 vs Celica W50 vs P51 ratio spread. Any experience or input? I am leaning toward installing the P51 because it will be unique.
    The crossmember swap will make life a lot easier for exhaust system routing. I have long tube 4-1's and Doug Thorely tri-Y's to use. The physical conflict was that every one of those collectors was aimed directly at the old crossmember which had no arch/relief. Now that problem is resolved.
    Good luck with your projects.
     
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  6. MrDinkleman

    MrDinkleman Addict

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    Where/how did you find a P51? I thought those were only attached to the 18RG?
     
  7. David Woods

    David Woods Newbie

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    Yes 18RG. I bought two 5 speeds a few years ago that were the length I needed. They were very similar in appearance but I researched extensively and one is a P51. The casting numbers tell but now that I compare them there is an easier way to tell them apart: on the tailshaft housing at the output end on the left side there is cast a the perimeter of a square with about 3/4" sides on the W50; the P51 just has the left vertical and bottom sides of what would be the same size as the W50 but looks like an "L" as it is missing the top and right sides of what would be a square.
    I'll probably put in the P51 and see how it drives. I can swap to the W50 if I don't like the ratios or the Porsche synchro rings of the P51.

    I like to keep it one-off. Like the Conquest ESI-R 16" staggered wheels. The staggered Pantera 15" wheels are getting winter tires on them.
    This is a lightened Chinook only used for road trips/camping.
     
  8. Perkolator

    Perkolator Toyotaholic

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    The lower 1st gear ratio of the P51 might be a good idea for your heavier Chinook body

    I still haven't done my exhaust - no time. All my time is going toward yard work these days, oh well
     
  9. fred heath

    fred heath Addict

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    The chinook body is actually pretty light. I run the L43 4 speed in my Galavan and find it’s geared perfectly. These little motorhomes are never going to get above 70mph. Even with a bigger hp engine they’re aerodynamically unstable at anything over 60mph. If the chinook has the pop top roof, you’ll probably be leaving it on the highway somewhere.
    Only advantage to the 5 speed is the lower ratio of the 5th gear. Great for flat cross country driving, but not that useful for local travel. If you have the L43 now, I’d keep it.
     
    Last edited: Mar 17, 2021
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  10. David Woods

    David Woods Newbie

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    Yeah, tell me about the yard work - I have been doing it now full time everyday. If I take a day off I am too sore to do anything at all (except whine).
    I'm following up: trans crossmember from '78 SR5 long wheelbase was a good source for me for what I was looking for. I think the truck had been undercoated and never washed underneath so there was a lb. or two of dirt/gravel stuck onto it.
    Were there 1978 Chinooks built on SR5 long chassis? That is probably addressed on a sub-forum...I'll have to search...
     
  11. fred heath

    fred heath Addict

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    Toyota sold 2WD cab and chassis separate from their pickups. They were sold to places like motorhome manufacturers, U-Haul and some commercial applications. They’ve based on the long wheelbase chassis usually with the GO82 rear axle setup.
    If your chassis ID starts with “RN28” this is what you have. They were sold with both 4 speed and 5 speed transmissions.
     
  12. David Woods

    David Woods Newbie

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    The '78 donor truck for the crossmember and W50 I got was a GO82 (4.10/8") truck. My '75 is missing the door jamb tag and I can't find an underhood tag. I had read that the oil drain in the 8" differential housing is located differently from the 7.5" housing and that they can be identified that way.
    My '75 has a chinook tag on the drivers door, id is RN28 but there is no trans/axle code on the tag. I'll have to go back to the JY to see if the drain hole location corresponds to mine or not. I may buy the jy 8" diff anyway as a spare to install LSD unit and install rear discs. The diff housing drain hole on my '75 is located toward the passenger side from midline. I read that 8" diff drain plug is toward driver's side of midline.
     
  13. fred heath

    fred heath Addict

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    There should be a metal plate or tag inside the engine compartment (mines on the left inner fender). All the chinooks I’ve seen are built on the 2WD c&c. This means your chinook probably also has the GO82 rear axle. I’ve attached a copy of my chassis ID tag. You should have one similar in the engine compartment. EA06C29B-B32A-47E8-A218-8ADAED085FE2.jpeg
     
  14. David Woods

    David Woods Newbie

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    Thanks Fred. A Chinook factory decal is on my door inside face. I'll see if I can send a photo.
    Do you have a GO82 vehicle? If so, which side of midline is the differential case drain plug on, driver or passenger side?
    Thanks
     
  15. fred heath

    fred heath Addict

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    Forget the chinook decal. That was added by chinook when they built the coach.
    All early Toyota trucks (pre VIN) came with a metal plate inside the engine compartment which acted as an identifier. Your truck should have one somewhere. This plate will identify which transmission and axle your truck has.
    As far as the GO82 axle, I scrapped mine years ago and installed a GM 14 bolt, 10&1/2” ring gear ff axle in its place. The GO82 axles had a recall for breaking if used with duel rear wheels. If your chinook has duel rear tires you might want to change the axle. Single tires were fine and not subject to the recall.
     
  16. David Woods

    David Woods Newbie

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    Thanks.
    My '75 is missing the metal plate(s).
    No, I have single rear wheels. Even still, I'd like to know (without dissecting it) which differential, 7.5" vs 8", I have in my '75 with the drain plug to the passenger side of midline.
    Are the GM 14 bolt axles common with disc brakes and LSD's?
     
  17. fred heath

    fred heath Addict

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    Most likely you have the GO82 rear axle. The only repair parts different from the 7.5” would be the axle shafts and r&p. Brakes, wheel bearings, wheel cylinders all interchange. The 7.5” has unequal axle shafts and smaller carrier splines. 8” uses equal axle shafts and a beefier diameter.
    If you have factory singles, no need to upgrade the axle. 8” is plenty strong.
     

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