View Full Version : Rivergate Conversion on a MK1 Midget??

03-27-2010, 10:30 PM
I have been seriously considering doing a Rivergate 5 speed conversion on the Midget. Has anyone done one on a early car (Bugeye or side curtain Spridget)? My car has the original 10CG engine in it. Was the conversion as easy as they say? Any tips if I do decide to go for it? Advice on things like - Should I go with the original slave cylinder or the one available from them? Pros - Cons - Little things you discovered first hand ect... would be appreciated.


03-28-2010, 04:11 AM
Your car is too nice to cut. There's no way I'd do it on your car. I'm not a purist, but your car needs to be preserved.

Trevor Jessie
03-28-2010, 07:34 AM
On your car I would install the engine and transmission separately so that the heater shelf does not have to get bent. I didn't use their slave, it depends on the diameter of your current MC. And... you will want the speedo adapter. You'll also want to get a spare shifter cover to modify to allow they modified shifter to work. Oh... and a spare shifter so that you do not have to cut up your original.

03-28-2010, 08:19 AM
Not sure of your intention, but most street rivers want the 5 speed for reduced cruising RPM.

You can get virtually the same benefit with a 3.9 (or even 3.7) final drive. Way, way easier and cheaper.

The A-Series engine is a torquey bugger....it can handle the taller final drive.

Actually, one my favourite transmissions is the ribcage that comes with the later A-Series engines.
That's a nice, simple swap if you still have the old-style smooth case trans.
I wish I could run a ribcage trans in my race car, but it has a 1500 engine and uses the cheesy BL "Marina" trans.

03-28-2010, 09:01 AM
Thanks guys, this is what I was looking for. I am also thinking about the 3.90 swap (actually leaning more that way due to the cost).
According to the Rivergate website, The kits have been modified so the heater shelf does not need to be bent anymore, and the only cutting is to the Datsun tranny. Apparently you have to do some grinding on the case.
Believe me Kellysguy, I'm not going to do anything if I have to cut the car.
My car is a 63, made a month and a half after the changeover to the 10CG and ribcase tranny. So it already has the ribcase upgrade, albiet, an early one. Is there a significant difference between the early and later ribcase trannys?
I have noticed mine is a bit noiser in the lower gears than newer ones (later 1275 cars), but that could just be this particular one.

Trevor Jessie
03-28-2010, 09:47 AM
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]According to the Rivergate website, The kits have been modified so the heater shelf does not need to be bent anymore[/QUOTE]

Sorry, but you will still want to install them separately. It is not difficult and only takes another 15 minutes or so.

BillM (who is busy at the moment) has a 1098 with a 5-speed. (I do not know what rearend he has)

03-28-2010, 10:12 AM
No cutting or bending required anymore it slips in all be there is some fanagling.
IF you plan on crusing broadway or the loop thru oak park and then blast up to lake Metigoshe for a weekend at the four seasons then me I would go with the 5 speed. If your under a few thousand miles a year then maybe its not a big deal. For me it is great! full sync all 5 gears reduced cruise RPM way quiter drive train. Did I mention full sync gearbox yea... It is by far the most bang for your buck improvment/update to enjoy driving your car it just makes things less....tense.
I enjoy hearing my engine and SU's sing not so much a clunky old gear box.

03-28-2010, 11:45 AM
My smooth case box only makes a wine in first gear and guess how much that is used. Now I will admit that it is a new smooth case. I got lucky.

03-28-2010, 12:19 PM
I have a 1098 with a 3.9 and I don't feel like I need a 5th gear. I drive on the highway a few times a week and it's pretty ok in 4th. If you like driving at 70+ for extended times I can see why you'd want it but I don't do that often. One thing I do notice is that driving in traffic at 30mph-35mph, which is a very common speed in everyday driving for me, is a little uncomfortable as it's right between 3rd and 4th gears. Anybody else ever notice that?

One small difference in the early/late ribcases is the reverse light switch. Your box doesn't have one unless it's already been switched to a later model.

03-28-2010, 02:08 PM
The more I read, the more I think that the 3.90 swap may be the way to go. Financially especially. I don't do much interstate driving, mostly back roads, 60-65 max, and 150 miles or so is about the longest without a stop. 2000 or so miles a year (mostly summer obviously). But, we are thinking about the 50th in Wisconsin next year :driving:.

03-28-2010, 02:48 PM
I've one of each, 5sp and 3.9 ribcase. If you have to cover some interstate the 5sp can't be beat but if you are on two lanes the 3.9 setup is fine. Personally I preferr staying on two lanes but if you have to get on the interstate with the 3.9 you can keep up. Both cars have 1275's and the 5sp has a 4.22 diff. You don't want to gear too high for your power. The 5sp car would'nt want a higher diff in my opinion. Course the engine is stock.
BE with 3.9 setup
66 midget with 5sp

03-28-2010, 06:04 PM
No cutting or bending required anymore it slips in all be there is some fanagling.

You sure about that? I thought you had to cut out the original trans mount area and weld in a new cross member.

Bryan, I have a 3.9 in my car now. W/ a 22.5" tire (175/70/13) 4k yields 68 MPH (speedo says 70, but caluculator says 68.)

Do a 3.90 or 3.70 first, they are cheaper and you can alway unload them if you change your mind.

Go here and play around. Scroll down to see the results.


03-28-2010, 07:43 PM
Search completed listings on ebay and there is a 3.9 that didn't sell for $89.99 and $27 shipping. Hopefully I'll be picking up two parts cars this week and maybe I'll have one for ya. I have one here but found out the hard way it's got a bent pinion shaft. Just swaped my old one back in.

Trevor Jessie
03-28-2010, 09:15 PM
A Datsun tranny can fit without modifying the car structure. With the stock 1275 and 3.9 rear end, my midget could cruise in 5th gear at 70 mph (3500 rpm) and pull hills without any problems. Certainly I did encounter some long steep grades that required gearing down ... but that happens with modern cars too.

03-28-2010, 09:32 PM
Does that count for RB cars too?

03-28-2010, 09:47 PM
I think the only option for 1500 cars is to convert to the Spitfire tranny with OD. That does require cutting the bottom and modifying the tunnel.

03-28-2010, 09:59 PM
Billm has a 1500 engine laying around so he might be able to make a plate fer me. I aint cuttin' nuthin' !

03-28-2010, 10:01 PM
Not getting to far off topic but I have a question:

Any MPG changes noted going from a 4 spd to 5 spd
Any MPG changes noted going from different gear ratio in rear

Other words which is best trans/gear combo for max MPG

03-28-2010, 10:07 PM
Does that count for RB cars too?

The best option for 1500's is the Ford T9 transmission - here it was on the Sierra XR4Ti - in England they were on everything. They do require surgery though but if you are willing are a much cheaper option than the Datsun is for the 1275. Rich Ball is experimenting with a Hyundai Pony with Morris providing parts and me cheering - we'll keep everyone posted on that. I was at a car show the other week and asked a transmission guy - he thought maybe a Ford Courier and I've always also wondered about a Chevette but really am not in the position to experiment.

03-29-2010, 06:08 AM
No cutting or bending required anymore it slips in all be there is some fanagling.

You sure about that? I thought you had to cut out the original trans mount area and weld in a new cross member.

The Ford T9 kit for the Spridget requires the center of the transmission crossmember to be cut out and another section put back in. I don't think it needs to be welded in (although welding might be stronger.) I will have to dig out my instructions. I don't have it in the car yet. Working or replacing the floorpans and the crossmember. Mine were rusted out (floor pans AND crossmember!)

The Datsun kit does not require any cutting on anything UNLESS you want to use the original starter, then the Datsun bell housing has to be cut.


03-29-2010, 08:58 AM
I won't cut period! If BIllm will make me a plate, I'll go Datsun only if I don't have to cut my car.

03-29-2010, 01:52 PM
Last week I was looking at putting the Datsun tranny on the 1500 and found that the 1500 flywheel is too big to fit into the Datsun bellhousing so that exact combination is OUT.
Next option will be to look at a different(smaller diam) flywheel that also fits the 1500 crank or a tranny with a bigger bellhousing (Datsun B210 or 510 maybe) but it also needs to fit into the trans tunnel in the car so that is iffy.
I'm working on it but running very slowly since other things are taking time too right now.


PS Trev- I have a 1275 w/Datsun 5 and 3.9 diff
BillL has the same but with 1098.