I've currently got a mostly stock L48 with the TH350 trans. The trans leaks basically continuously, I suspect because a couple of the bolts on the pan are stripped and won't actually hold in place. I've had the seal replaced a few times(2x professionally). Still leaks pretty regularly so I'm not sure what I need to do to fix it. I really could use better gas mileage if I'm doing major transmission work.

This leaves me at a fork in the road. I've got a friend who is willing to help me replace the transmission over the christmas break. So I can put a new/rebuilt transmission into the vehicle.

My question is basically what should I do?

Couple options as I see it.
1.Ignore the problem. I'm not sure how bad the problem really is, which is why I'm hoping for some insight here. Do I need to do anything about it at all?

2.Rebuild. Either do it myself(hahahha yeah right) or farm the job out. I'm not sure what this would cost, and would it even fix the problem(always assuming I HAVE a problem)?

3.Direct Replacement. Find a TH350, either used or new?/rebuilt and put that into the car in replacement for the one that is there.

4.Upgrade. Need to pick a different trans.
4a. 700r4. Good first gear, and overdrive.
4b. Richmond Overdrive 6Speed. I've always wanted a 6-spd, but I'm assuming this will be a MAJOR project to get into a born auto car.
4c. Something you reccomend.

5. Do I keep the original trans for originality or do I give it in as a core?

I'd like more gears than the 3 i've got now, and I could definitely use better gas mileage from an OD Trans.

Scot
Confused.

If you want to keep the trans you have the threads can be repaired with heli-coils (spelling???) Go to any autoparts store and ask for a thread repair kit, they will know what you need. The kit comes with a drill bit and tap and some steel coils that get screwed in to the striped holes.
If you realy want to replace it with an overdrive trans then the 200R4 is a lot easier then the 700R4. Its almost a direct fit for the TH350.

Welcome to the world of "fluid leaks". I'm sure a long discussion on valve cover leaks, oil pan leaks, etc. could also be discussed at length.

Let's first talk about the tansmission leak. You probably have a few location choices. 1) Front seal-where torque converter attaches. 2) rear seal where drive-shaft connects. 3) transmission pan 4) auto-down shift connection to engine - black line on right side of transmission. 5) speedometer connection-left side, behind transmission pan.
Depending on which one or ones are leaking, depends on time, level of problem and money involved.
The front seal would require the transmission to be removed. The rest do not.
As a side note, I do not know if cork gaskets were used in the leak fix process, but if they were used, and synthetic transmission fluid was also used, it is not uncommon for the lower viscosity synthetic fluid to leak past cork gaskets. If not, and the leak is coming from the pan, all that may be needed is to take off the pan and either straighten out the lip or replace the pan. Both are cheaper the a transmission replacement.

Second, transmission change. I still have a TH350 with a TCI aluminum pan. When driving down the road at 60 with an RPM at 3000, I also think of a transmission replacement.
However, money for the transmission, new drive shaft and possibly a new crossmember cause me hesitation.

I have a '74 L-82 with TH-400 that also leaked like a sieve. About a year ago I took it into Mr. Transmission thinking it was just a pan seal, cost about $70. When they got it up on the hoist they found it was leaking from every seal and gasket and should have a complete seal kit, cost about $300. Then when they got it apart, the bottom of the pan was covered with a 1/2" of gunk and suggested checking the clutch disc's while it was apart.Well you guessed it ... the disc's were all burnt or badly worn, so $1300.later I got a new pan gasket.This was in Can. dollars. What I'm saying is be prepared for the worst!!!

If you drive your car daily or near-daily, give consideration to converting to an overdrive transmission. If it's occasional pleasure driving, you'll not likely see any financial benefits from better gas mileage, etc. Also, if you want an overdrive trans, you'll likely end up paying more since rebuilders want an identical model transmission in trade.

If the tranny is running OK otherwise, try the heli-coil route as was already mentioned. That may take care of your problems. Even if it just slows down your leaks, it will give you time to determine your best course of action.

If I replace the transmission, I am definitely looking for an overdrive trans.

What makes the 200r4 trans easier to install than the 700r4? What are the 1st and 4th gear ratios for the 200r4 as compared to the 700r4? (I'd like a little kick off the line, and have been told that the 700r4 will do that quite nicely).

What I've seen so far is that a Manual conversion is not something worth considering?

Are there any 5 speed auto trans that have a "better" final drive ratio than the r4 transmissions already discussed? Or a 4 speed.

I drive the car a LOT when I'm in the same state(3months of the year). Sometimes 1000+ miles in a week. Once 700+ in a day. So I'm sure that an overdrive trans is a good idea! I think I get 60mph @ 2500. Different rear end maybe?

I'll look into the Heli-Coils. I know the threads are stripped from a few bolts and that the fluid drips from those bolts. My thought is that they are the problem, but I have no idea.

The cork gasket with synthetic fluid. Presumably the shop that did the repairs would have known this problem and not combined them? (assuming of course that you have to replace the fluid to replace the pan gasket?)

Scot

Ratios for the 200R4:

1st 2.74
2nd 1.57
3rd 1.00
4th .67

Ratios for the 700R4:

1st 3.06
2nd 1.63
3rd 1.00
4th .70

The 200R4 is pretty much identical in size to the TH350, so no need to shorten the drive shaft. Redwingvette has installed one of these in his '73, so he can give better info than I can. I'll be swapping my TH350 for a 200R4 as soon as I've got the money all in one place.

The 700R4 will be quicker off the line all other things being equal, but with the overdrive you could go to a 3.55 rear and get quicker launches and still have milage in or near the 20mpg range.

Keisler makes a kit to swap from an auto to a T56 six speed, but it's $5,000. It would take a looooong time for that to be cost effective, even with a daily driver.

Good luck on your decision! Let us know how it turns out!

The cool factor of the 6-speed is worth something though! Might look into the Keisler conversion, see what's needed and try to make it happen with something cheaper but same size(Richmond 6-speed was mentioned as fitting into a 4-speed in another thread and seems to sell for $2500ish.) I'll definitely let everyone know what happens. How much of a difference is .70vs.67 when it really comes down to the wire? Keisler's 6-Speed has a .5:1 final drive ratio. Comparing that to .67. I know nothing new, but anyone have any thoughts?

Scot

|UPDATED|12/7/2003 11:42:14 PM (AZT)|/UPDATED|

If you want a stick, I'd look into the Kiesler conversion. I like an automatic because you don't have to shift all the time (I'm lazy OK). I have a 700R4 in mine and love it. You can get all the swap parts from BowTie Overdrives and I would source the trans locally. I see some action on the 200R4, I just don't have any experience with it. If you plan on making a lot of power I'd stick with the 700. My .02

If the heli-coils don't work for you, there is another albeit crude way to stop the leak and maybe not need to remove the pan. Clean the holes well with a rifle bore brush and laquer thinner. Make a stud from the same thread rod or long bolt with the hex head cut off. Coat the hole with a liberal amount of JB Weld. It is an epoxy like material that the manufacturer say can be drilled and tapped. Coat the threads not going into the hole with paste shoe polish and cover with tape. This will keep the stuff from sticking all over the threads. Give it 24 hours to harden, remove the tape, wipe the threads and turn a nut on a washer. If your leak is caused by the 3 stripped holes, this should be an easy fix to hold you over.

With all the miles you are putting on an engine rebuild can't be too far off. At this time the tranny swap would be the best time. An upgrade to an OD unit would be the way to go. I am not familiar with the 200R4 but if it is a direct bolt in it would be my choice. A taller rear gear would compensate for the higher first gear if that is a concern. I have a 5.13 gear differential that I would trade for a good 3.08. You will pull tree stumps on the low end, but don't expect much more than 80 mph at top end. Good luck stopping that leak and whatever you choose.