Engine and Transmission Tech

Hi

I'm an Englishman living in New Zealand and I've had a lust for Rover V8 engined cars for some years culminating in a highly modified 5.1litre engined TVR.

Before I sold the TVR I removed the engine and put it into storage for a future project. I now have a Rover P5B Coupe that I have big plans for!

With the ex-TVR Rover engine tuned more appropriately for a big saloon I hope to create a Bentley Turbo-like P5.

In order to accomplish this and keep the basic character of the Rover I've decided to keep the configuration as is - that means a beefier rear axle (Toyota Hilux with LSD converted to discs) but leaf springs and torsion bars.

One area of weakness is the transmission. The BW35 was at it's limit with the 3.5 Rover/Buick engine so the massive torque from mine will destroy it in seconds. On top of that the gearing results in a very busy motor at motorway speeds and the shift quality isn't great.

So I've decided to fit a 4L60E utilising the megasquirt transmission controller (megasquirt will also control the engine). The only trouble is finding an adapter to couple the Rover to the GM gearbox. One company I know of in Australia that lists such a kit charge a lot for it and can't tell me exactly which model of gearbox I can use! I've pretty much given up on getting the info I require from them.

I'm also curious to find out whether the GM180 'box fitted to the SD1 could provide the necessary solution. I believe this box may have a detachable bell-housing that will bolt-up to the 700R4/4L60E. Can anyone confirm this?

I'm looking for the simplest, strongest solution that will give me an overdrive 'box capable of upwards of 400lb/ft. Does anyone have any ideas?

Oh and before someone suggests it, yes I have looked into using the ZF 4HP22/24 but the torque handling of that box is just too limited for my application even with upgrades.

Jim, Welcome to our forum. I've seen 4L60E with detachable bell housings? Jim Blackwood would know better than I. I believe he is our consumate, auto transmission Guru. Once you have a suitable transmission, I suggest a read of his latest auto trans. project,you'll be closer to fabbing a suitable bell housing.Perhaps you can adapt that BW 35 bh. to fit ? Good Luck, roverman.

Interestingly enough, the BW35 is more than capable of handling your engine's power, as they were used behind all manner of American V8 engines in full sized cars and trucks. For quite a while it was the mainstay of the Ford lineup, and I-H used it as well, behind a beast of a 392 cu.in. V8 in a 6000 lb vehicle. I understand it was even used in some school busses. So strength is not really the issue. However the gearing is limited, as you say and there are numerous better choices. As I recall, it does have a removable bellhousing with a concentric circular mating flange. This broadens your potential choices dramatically, particularly if you are willing to look at the Aisin transmissions used in modern Japanese cars and trucks. There are some particularly good 4, 5, and 6 speed transmissions which use a similar removable bellhousing, meaning you might get by with a fairly simple adapter ring or some fairly inexpensive machining of the bellhousing. I'd begin by looking at the Lexus lines. I have a 5 speed on the bench and could measure the diameter of the flange for you if you like.

The problem with the BOPR engine is that it uses a unique bellhousing pattern. Since GM quit using that pattern in '64 the only source for mating transmissions has been Rover or the aftermarket and aftermarket bellhousings for auto boxes are very hard to find. I'm still not aware of anyone who makes a production piece, though there may be one out there somewhere, perhaps down under. So starting with your old bell is probably the best approach. But I'd suggest you broaden your search for a suitable transmission. There are several which are better choices than the old standby 4L60 (700r4) and 2004r, neither of which fits without an adapter anyway. Plus if tunnel clearance is an issue, the newer transmissions have nice narrow pans. The problem with the newer transmissions of course is the transmission controller. Some aftermarket controllers are available, and some stock controllers are usable, but research this area carefully before making a choice. Also I'd suggest you identify your candidate by serial or part number before buying to be sure you are getting the one you think you are.

Edit: I do believe there was a 4L60 which used a removable bellhousing. It was a limited application and I've never seen one and can't remember any more than that about it but it could be the application you mentioned. It is so scarce as to be considered nonexistent up here.

JB



Edited 1 time(s). Last edit at 10/15/2010 09:32AM by BlownMGB-V8.

I believe it is actually the later 4L65E transmissions with the bolt-on bellhousing.

Jim/Jamie, don't know how much room in the tunnel for a larger trans. I use the Volvo/Celica/Toy. truck, AW.#3040 aod,(blue tag), quite compact.You will need the unit with a "throttle valve cable", as these requre no "electonic controller". Should adapt to your BW 35, bh. quite readily.Can't tell tell you the torque capacity of this trans. Good Luck, roverman.



Edited 3 time(s). Last edit at 10/16/2010 01:29PM by roverman.

Hi guys,

Thanks for the replies.

I never knew the Borg Warner 35 was used so extensively in the states. I thought it was developed for little engines - hence the fact it is always stated as being marginal for the 3.5litre Buick/Rover. I do know it was developed further for the Australian market and put behind some larger capacity Straight Sixes but I never knew it was used in a school bus!

Anyway, I guess the whole point here is that I'm after a 'box with a decent overdrive.

I have seen at least one reference to the bell housing from a GM180 (to Rover V8) as used in the Rover SD1 being bolted-up to a 700R4. It may be that 700R4s were more commonly available in Aussie with detachable bell-housings. That probably merits further investigation on my part.

As for using Aisin gearboxes, I'd have no problems with this. The only thing is, i'd need to be careful about which one I chose. Being in New Zealand, the market for spares is very small and items like the Lexus boxes would be very rare and very, very expensive.

The A340/A341 box used in various Toyotas may be worth a look. I presume as this was used on so many different vehicles over such a long period that there will be non-electronic versions around that will make installation a bit easier? The A341 was used in Turbo Supras so it should be able to handle the grunt.

Jeep Cherokee TCU box(87-94). AW4 same tranny as A340 Toyota. Only needs 3 wires and TPS(throttle positon sensor). A couple of them on Ebay or look on car-part.com.You could rig a manual shifter bypass switch for solenoid shift and rocker switch to lock the torque converter, not recommended in low.

Jamie,

early SD1's used a slightly different version of the BW35...Called 44? or 66, similiar to what SII & S3 XJ6's used...Those boxes always remind me of Taxi's, especially when slowing & they clunk back into 1st with that "signature" whine.

The later SD1, or more correctly 3500SE use a French built 180 or Trimatic (Traumatic?) . Not a bad box in the 70's & I believe some are still being used in drags etc. Trimatics were used on Holden 6's, 4.2 & 5 litreV8's before a switch was made to Turbo 400's. I recall Holden recast the block to Chev bellhousing so these T400's wouldn't fit the Rover anyway. Last of the injected Holden V8's used 700R4's.

The 700R4 used in the 3.8 V6 RWD Holden Commodore might possibly be a good fit with an adapter? 88-91 boxes had minimal electric's too. Should be plenty of VN Commodores for wrecking in New Zealand.

Does the AW4 have a Chrysler v8 type bell housing pattern, Jim N? If so, 83-86 Range Rovers would provide an adapter plate as they use a 727 Torqueflite.

I'd like to replace the standard 727 Torqueflite in my 85 Range Rover with a 4 speed. Would these be stronger that a ZF 4hp22 ?

AW4 has separate bell, Jeep is AMC . Toyota A340 is Toyota and Isuzu version is GM small V6. You could make a motor plate adapter or adapt a Rover bell to the tranny.



Edited 1 time(s). Last edit at 10/21/2010 01:15PM by mgb260.