Isuzu 5 speed...again

[jabingb]

I just acquired a '69 FHC and after driving it home from Seattle I'm determined to pursue the holy grail of a ~.8 5th gear. I have an Isuzu box for the project and would like to converse with someone here in the US that has successfully accomplished the conversion. There's a wealth of info here on the forum but it all seems to end around 2008, as well as "down under", surely there's more recent US activity?

[Famous Frank]

Hello Jerry,

I have installed an Isuzu 5 speed in my Elan but I have not yet driven it. I can have the adapter plate made up as I spent months with my local machinist and we have the program installed in his CNC machine.

Here are a few pics of the installation. ...... I think.

I too am looking forward driving an Elan on the expressway at less the 4 or 5 thousand rpm.

Frank

[tedtaylor]

frank, it appears the shifter is only slightly more rearward than original, so I suspect cutting into the center console more.
does the original drive shaft "slide" forward enough to bite the yoke OR do you have to use a different, longer driveshaft?

[jabingb]

Hello Jerry,
I have installed an Isuzu 5 speed in my Elan but I have not yet driven it.
Frank

Frank,
There's a fellow Elan owner here in the Bay area that is about at the same stage, was hoping to converse with someone that's driving one. Is your machinist interested in producing another adapter plate? Did you source a custom driven plate with spines appropriate for the Isuzu? And what about Ted's observation about the shifter appearing a tad behind the original?
Jerry

[Famous Frank]

Jerry, Ted,

Thank you for the questions. I spend hundreds of hours on this project and it's nice to get some questions, although it's now been sitting for so long I can't remember what I've done.

The shifter lever does sit approximately 1/2 inch or less farther back. The console hole is a no brainer as I manufacture new Consoles. i purposely don't put a shifter hole in them because of just this reason. People are installing different transmissions and you never know where the hole must be.

I even cut down the Isuzu Shifter Handle, heated it glowing red and reshaped it to look just like the Elan shifter, re-threaded the end, and then had it chrome plated. Took it to the Lotus Corps Club meeting a few years ago and no one knew it was and Isuzu.

The clutch disc I purchased from an old clutch guy here locally (who has since passed away and his building is now a new high rise) . It had the same splines but was about a 1/4 larger in diameter than the Lotus disc so I just put it on my lathe and cut down the OD. What can a little more asbestos dust do to me at my age anyway!

I struggled with the speedo cable but there are now some companies that will make an electronic speed and that's what I'm going to use.

I had a new driveshaft made because I'm using the Isuzu yoke with the Isuzu splines. The first one made up was a tad to large in diameter and I was afraid it could hit the frame so I added a little frame clearance where necessary and had a second driveshaft made up that appears will work fine.

I'm using a 3:77 rear end but the trans has a 3:32 first gear (if memory serves me.............hmmm, I'm starting to see a bunch of memory things here, ..............don't tell anyone) so it should feel and accelerate just like a semi close Elan trans with the 3:90 rear, which I've always liked.

I will check with my machinist on the adapter plate for a time frame and price. I've got well over $1,000 in mine but it was the first one. Yours should be less.

There is no weight penalty with the Isuzu. Although it has more stuff in it, the case is alloy. it might even be a few pounds less.

I had a different fabricator machine off the Isuzu bellhousing . He also checked out the trans internals which all looked fine. It came out great.

Here are a couple more pics.

Frank

[Famous Frank]

I did have to trim the metal part of the frame just a tad where the shifter assembly is located.

Frank

[jabingb]

I did have to trim the metal part of the frame just a tad where the shifter assembly is located.

Frank

Hmmm, wonder if this really can be accomplished with body on chassis, think I will try to reach out to Maurice again, although I think his approach was from a bare chassis as well. I'm not inclined to take the FHC body off so that may be an issue.

[Famous Frank]

Jerry,

I think it's doable ! Just curious, what did your Isuzu trans come out of?

Frank

[rcfurse]

Frank, Count me in for an adapter plate and a transmission if you can lay your hands on one. Let me know the numbers and I'll wire you.I had bought a Honda 6 speed box from the S2000 hoping I could work it but although it has a seperate bellhousing all the gearbox shaft bearings are located on the back of it. I have a Spyder chassis ready to trial fit. I would be delighted to handle the UK end to help you.

[jabingb]

Jerry,

I think it's doable ! Just curious, what did your Isuzu trans come out of?

Frank

Not sure, bought it in the 90s, no evidence of a model # stamped, maybe a tag that's missing? Ratios measured with 2 vise grips are approximately 3.125, 2, 1.375,1 & .8.

[Terry Posma]

I have completed this conversion about 2 years ago. I used a gearbox from a diesel. The ratios are slightly taller than the petrol version.

I used an adapter at the engine side but looking at this solution I would go with the adapter at the gearbox side as the Izusu bell housing is quite large and also requires a mod to move the starter motor. I used a concentric clutch throw out bearing.

The gear lever ended up about 20mm further back in the chassis and as I have made some of the 26r stiffening mods to the chassis required an extra bit of cutting. This took quite a bit of effort as I only wanted to cut just enough and no more. Gear lever is not angled back enough and so I can hit the dash with my knuckles if not careful. One of the many thing that needs a little fix.

The gear ratios for a diesel box are: 3.467, 1.989, 1.256, 1.00, .782. The petrol are 3.507, 2.175, 1.418, 1.000, .855. I have a 3.555 diff and it all seem to work ok. First is a bit shorter than a semi close with a 3.77 final ratio but the next 2 are a bit longer. Second and third very useable. Helps that the car has a 1720cc motor.

Much of the info I found came from searching this site. I have a copy of a manual for the box which was posted somewhere on this site as well. The ratios mentioned in the manual are incorrect.

[rcfurse]

Can anyone give any details of the Isuzu box? Which car/cars/trucks did it come from? is there a model or part number?

[Famous Frank]

Terry, nice write up and thank you for the update. I'm truly looking forward to mine.

You are correct about the shifter and the bellhousing. I resolved those issues by re-fabricating the shifter as I mentioned so mine should not damage my knuckles or the dash. And on mine, by machining off the bellhousing I was able to use the Lotus Ford bellhousing, starter, flywheel, etc. I installed a heavy duty fork but otherwise stock.

Although I haven't driven mine yet, I did test it with the help of Greg Zelazek. A friend of mine has a wooden box with a clutch pedal and standard clutch master cylinder. We hooked that up to the slave which is still mounted on the bellhousing in the stock location and tested the clutch release, etc. Put the trans in first gear, turn the engine over and watched the driveshaft turn. Pushed in the clutch pedal and the driveshaft did not turn. Magnificent peace of mind!

My trans came out of an Isuzu Impulse Turbo, .....the rear wheel drive model,...............I think 1987 or 88.

Any pics of your installation Terry? And if I may ask, what part of the world do you reside in?

I also have another out of a Isuzu pickup for a future build on another Elan.

Frank

[Famous Frank]

The ratios in the one I'm using are:

1st: 3.43:1
2nd: 1.96:1
3rd: 1.36:1
4th: 1.00:1
5th: 0.78:1

The 0.78 fifth gear with a 3:77 diff should make for some nice cruising, especially here in the Atlanta area where every idiot in the world is here doing 80 to 85 mph, and semi trucks doing 80 also.

Frank

[The Veg]

Pretty sure that my Plus 2 has a 3.77 as well...hmmmmmmmmm...