Pre-emptive transmission rebuild?

"StudyStudyStudy" (jesterjin) 07/22/2016 at 14:30 • Filed to: None

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Hey guys,

I pulled the 7mgte engine out of my Datsun 240z and now I am staring at my transmission. The bell housing bolts were not as easy to get to as I had hoped. Might be possible if you dropped the tranny down a bit, but otherwise super difficult, I had to use just a socket as a wrench wouldn’t grab and the ratchet would hit the firewall, and turn it by hand after I got it loose to get the bolts out.

My fear would be that I manage to get the engine together, put it in and have the transmission go bad soon after. Some say they have never had this happen, others say it will happen eventually. The benefit is that my car weighs about 1/2 as much as the supra so there should be less strain on the transmission. I kept my tires skinny so that they will also act as a relief. My concern is that when I got this transmission it had been behind built supra motors according to the previous owner, being drenched in oil I can only imagine what kind of life it has been through.

The transmission is an R154 from a toyota supra. They are known to be stout until they are not. There is a weakness in the oil delivery to a thrust washer causing that to give which then causes an excess clearance causing the actually gear to wear out. When this happens the car will start popping out of first and then gears will start wearing out. New gears if available are about $500 a piece.

My transmission currently does not have the issue of popping out of first gear. It shifts ok, although getting into reverse is a bit difficult sometimes.

Driftmotion does rebuilds including the upgraded weak parts (chromoly thrust washer, billet bearing retention plate), new forks, new bearings, new seals for $1200 total ($700 for parts, $500 for labor). Shipping to and from is probably going to run $200-250.

What would you do? Don’t fix it if it ain’t broke? Fix it because it will be a pain in the ass later? I am super on the fence here.

WiscoProud > StudyStudyStudy 07/22/2016 at 14:35

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If you're already having issues and it has a questionable history, I would go ahead and do it for the peace of mind.

crowmolly > StudyStudyStudy 07/22/2016 at 14:36

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My first thought is about creative ways to pull the bolts.

As an example, pulling a bellhousing in an LS1 Camaro/Firebird can really suck if you don’t use wobble sockets, extensions, and u-joints. If you do, it’s not that bad.

Can you come up with a combination of tools to make removal easier? I want to say don’t rebuild and save the ~$1500.

Your reverse gear might not be synchro’d, in which case it will always be a bit difficult.

SidewaysOnDirt still misses Bowie > StudyStudyStudy 07/22/2016 at 14:38

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For that price, how much is another tranny? If you’re going to be dropping it anyway, why not drop it once it’s a problem and put a newer one in?

just-a-scratch > StudyStudyStudy 07/22/2016 at 14:38

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How much does it cost to replace the transmission of it fails? If it's$2000 or more I would go ahead and rebuild now. Get potential headaches out of the way.

StudyStudyStudy > crowmolly 07/22/2016 at 14:40

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Short of just drilling access holes from inside the car I’m not sure. I imagine if I took it to a shop they could undo the trans mount lower the trans and use a really long extension to get at the bell housing bolts with it tilted. Downfall of moving the engine so far back :(

Thanks for the suggestion, so far 1 vote for, 1 vote against.

StudyStudyStudy > WiscoProud 07/22/2016 at 14:41

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Questionable history is for sure a concern, some other friends have pointed out that, that in itself might be something too, like what if it already had a rebuild or something.

Thanks for the input so far 1 for 1 against :)

StudyStudyStudy > SidewaysOnDirt still misses Bowie 07/22/2016 at 14:43

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That has occurred to me, another tranny would be $1,000 for a used questionable one. I could just buy another used one and send it out for a rebuild and throw it in when I need to I suppose. On the flip side that would also be a 150lb, $1000 piece of metal rolling around my little space.

Thanks for the input, 1 for, 2 against now

StudyStudyStudy > just-a-scratch 07/22/2016 at 14:46

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It would depend. If I caught the failing washer, then I could get away with just a rebuild, $1500 or so. If I didn’t catch the failing washer, then probably the first gear is going to need replacement which would be $2000 or so. If I didn’t catch the failing washer and didn’t have the time to deal with it, probably $3000 to have a shop pull it, rebuild it, and put it back in.

2 for and 2 against now.

SidewaysOnDirt still misses Bowie > StudyStudyStudy 07/22/2016 at 14:48

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That sucks. Figured it was common enough for them to be way lower, but if Supra people use them, maybe they’ve all been destroyed.

crowmolly > StudyStudyStudy 07/22/2016 at 14:48

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Eh, consider me on the fence :)

What does the trans fluid look like? Clean, no particles?

iSureWilll > StudyStudyStudy 07/22/2016 at 14:50

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Can’t help much with the rebuild stuff but...

Most shops will unbolt the rear trans mount and support the back of the trans with a jack. Lower it until the trans hangs, then raise the jack up a hair to support it. Then you should be able to use extensions and a universal joint to get to the bolts. You won’t be able to see them, but you can use your right hand on the ratchet and left hand up on the socket while you feel around for the bolt. Stabilize the socket with your hand if you can while you torque on the ratchet and you should be golden. Its easier than it sounds.

StudyStudyStudy > SidewaysOnDirt still misses Bowie 07/22/2016 at 14:51

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I think the problem is that it is one of the few manual transmissions that has the potential to hold up quite a bit of power so every car with a 2jz that came with a W58 or an auto target them for the swap, SC300, IS300, GS300, Auto MK4 supra, Auto Mk3 supra, so on and so on.

I remember buying my 5 speed for the L28 for $100.

StudyStudyStudy > iSureWilll 07/22/2016 at 14:53

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That is what I imagine, the concern is that the engine being so far back might hit the firewall before it can tilt too far down. Also I don’t know of any shop that would take out the transmission, package it up, send it out to be rebuilt, and install it without charging me a kidney, and I’ve heard some experience is needed with these transmissions or a rebuild will be right around the corner.

StudyStudyStudy > crowmolly 07/22/2016 at 14:55

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Yea, I find myself so much on the fence, every time I think I figured it out, I hop right back on.

Trans fluid has been changed 3 times or so in the 1000 miles it has been driven. Redline Mt90 has been in it the last two times and both times came out pretty clean.

LongbowMkII > StudyStudyStudy 07/22/2016 at 15:05

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If you’re able, keep an eye out for people buying 1/2jzs from Japan. Often they are sold with the transmission iirc. Or maybe just find someone who wants a jdm jz and split the cost of shipping?

iSureWilll > StudyStudyStudy 07/22/2016 at 15:07

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The head(s) will probably be what rests on the firewall and you should still have some room to get at the bellhousing bolts. You may have to play around a little bit to get the right angle.

Good luck!

DynamicWeight > StudyStudyStudy 07/22/2016 at 15:18

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Is this a daily driver or fun weekend project? DD I say replace now. Project I say wait till it breaks. You can spend your whole life trying to find every little issue and fix it. The internet is full of things like this where “Oh yeah, they all break like that” but in truth it really only affects some small percentage of cars.

Also depends on where you are financially. If you didn’t fix it and it broke, would your first thought be “Shit! This is gonna cost me!” or “Shit! Now I have to pull the damn thing again.”

Actually the more I think about it, 1500 doesn’t sound like all that much for a rebuild. I say go for it. Then it’s all minty fresh.

Also, another dumb thought, could you cut down a socket to get a ratchet in there?

StudyStudyStudy > LongbowMkII 07/22/2016 at 15:25

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Hmm haven’t thought of that. There is an importer here, but last time I checked they wanted $1500 or so for a very used looking transmission. Thanks for the thought!

StudyStudyStudy > iSureWilll 07/22/2016 at 15:26

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Thanks, the dilemma is that right now I took all those bolts out to remove the engine. It would just be a matter of undoing the two transmission mount bolts and sliding the trans forward to disengage the drive shaft. Later it would be a bit more difficult...

iSureWilll > StudyStudyStudy 07/22/2016 at 15:35

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Ah gotcha. Sounds like you got it under control.

StudyStudyStudy > DynamicWeight 07/22/2016 at 15:37

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Definitely a weekend/project car type of deal. Doesn’t have to be on the road all the time and I do have the best package AAA offers.

I hear you on that. There are so many contradictory things, some say it only fails when you drop the clutch, others say their grandma was driving the car and it failed, others say they drag race every weekend and it holds up fine. Not sure who to believe, but there are several intelligent people who have found fault with the part and photographs to back them up so I am more leaning towards an eventuality rather then a possibility.

I have the money, I wouldn’t have to put it on a card or anything, and I have a fairly large overtime check coming in a couple months which would probably cover everything plus a large portion of the engine rebuild, I just wouldn’t get to pocket much of that. If I put it off it would definitely be a real bummer as jacking the car up to a height where I could tilt the trans back just to get the trans out leaving the engine in would require new stands and taller ramps and such.

$1500 is very affordable compared to what the quote was to fix my automatic in my daily driver. Which is also part of it, is it so affordable that I should just do it? Or am I just throwing money away. Or will I even want this driveline in a few years time, or will I even have this car. Lots of questions with lots of answers.

If I could get a wrench on it it would be easy peasy for a future removal. Problem is it is the american spec metric bolt so the heads are massive. I can get a ratchet on it, but after a couple turns the handle gets stuck against the firewall. I could find J-spec headed bolts to probably solve that problem for the future. Right now though it is an inconvenience I have already dealt with since the engine is already out. Further adding to the dilemma.

DynamicWeight > StudyStudyStudy 07/22/2016 at 16:21

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Can you get a ratcheting wrench on it? The head of your socket wrench can’t be that much smaller than the head of the ratcheting end of the ratcheting wrench.

I bought this set and have never looked back. Not sure if it has the size you need:

https://www.amazon.com/GearWrench-20-…

If you’re questioning whether you’ll even have the car.... more and more I think wrestling with a few bolts on the off chance something does break, is the way to go. Also, even if the shop you’re thinking of using is highly rated, there is still a chance they could screw something up. I don’t have a ton of first hand experience here, but the consensus amongst the older folks is that the factory putting together a bunch of nice new parts, is going to generally come out better than a bunch of (perhaps quite talented, perhaps not) dudes putting together a bunch of old and new pieces.

StudyStudyStudy > DynamicWeight 07/22/2016 at 18:38

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Can’t even get a regular wrench on it which means a fatter ratcheting wrench is out of the question.

I have thin walled sockets I use for this particular situation. A regular heavy duty socket wouldn’t fit. Pretty sure I can find some smaller headed bolts if I looked around enough.

If it was just another transmission I would agree, but this has a pretty well documented failure cause. That is true it could always come back worse, even with the best intensions.

Bah, more pros and cons to weigh.